Remote Control Remote Control System Solution Keyless Entry Compa
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Remote Control System Solution Keyless Entry Comparison Infrared versus Systems Infrared System System Dedicated Transistors Keyless Entry/ Remote Control U2740B Transmitter Remote-Control Applications Introduction General Information Remarks U2740B Remarks Demo Board Loop Antenna Demo Board Remarks Battery TEMIC's Demo Board Circuit Evaluation Description Starting Transmission Modulation Modulation Supply Voltage Development Customer-Specific Board Customer-Specific Modifications TEMIC's Board Using Different Crystals Different Design Different Values Loop Filter Spurious Emission Development Board Placing U2740B-Relevant Parts Placing Remaining Parts Performance Calculation Magnetic Loop Antenna Appendix Demo Board Schematic Demo Board Component Placement Component List Appendix Output Stage U2740B Single-Ended U2740B's Output Stage Components RF-Based Remote-Control Systems Transmission Frequencies Systems Further Boundary Conditions System Comparison Remote Control Concepts Standby versus Polling Concept Superheterodyne Superregenerative Receiver Comparison Operation
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Contents (continued)
TEMIC Receiver U4311B, U4313B, U4314B Parameters Receiver Frequency Response Data Filter Data Regeneration General AC-Coupled Data Filter Quasi DC-Coupled Data Filter Pattern Error Rate Measurements Operation Demodulator Characteristic Signal-to-Noise Ratio Operation Discriminator Characteristic Bandwidth Signal-to-Noise Ratio Circuit Diagrams Test Board Operation Test Board Operation Complete Remote Control System Circuit Proposal Transmitter Operation Circuit Proposal Superheterodyne Receiver Complete Link Summary Future Considerations Appendix Remote Control System: Receiver Front Complete Receiver Design Hints Introduction Circuit Arrangement Complete Receiver Front Remote Control System Circuit Alignment Description Circuit Diagram, Layout Component Placement Components 433.92-MHz Operation Components 303.85-MHz Operation Front Measurement Results Demo board with Part Microcontroller Demo Board Receiver, Part Receiver Measurement Results Appendix Components Complete Receiver 433.92 MHz, Components Complete Receiver 433.92 MHz, Components Complete Receiver 303.85 MHz, Components Complete Receiver 303.85 MHz,
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Remote Control
U431xB family designed realize lowcurrent remote control system. This system flexible with regard amplitude frequency modulation, different transmission coding wide range data rates. transmitter well receiver likewise equipped with surface acoustic wave (SAW) resonator frequency stabilization. both transmitter transceiver's front end, transistors S822T/ S852T used they well suited low-current operation. superheterodyne receiver based TEMIC's receiver U4311B. These monolithic bipolar technology include necessary parts from signal processing data output. receiver ICs, together with transistors low-power microcontroller M44C260, enable realization receiver with average current consumption approximately This outstanding feature achieved standby- polling concept conjunction with specific circuit arrangement. further type receiver U4314B which suited exclusively operation. achieves supply current below without sleep mode, also without baseband processing. U2740B single-chip transmitter automotive keyless entry. With on-board voltage-controlled oscillator (VCO), U2740B provides compact solution small form-factor designs with improved performance over SAW-based transmitters.
System Solution Keyless Entry
Batt BPV23FN U426B TSHA5200 "Super-het" MARC4 family, e.g., M44C260/ M44C890 encoder S822T S852T U2740B "Super-regen" Alarm S822T S852T Filter comparator DA5209/ DA5276 Ultrasonic alarm S822T S852T strip U4311B M44C260/ M44C892 Decoder control U2535B U2538B Regulator watchdog Reset
Door locks Trunk
Lights
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Comparison Infrared versus Systems
infrared remote controlling central locking systems cars standard feature luxury- midrange cars. will also offered lower vehicle ranges near future. remote control systems inexpensive, well experienced easily realized with conventional production techniques. Recently some areas, low-power radio links have replaced infrared systems. Especially market, RF-based systems offer advantage being affected dirt, snow. Nowadays, car's windows often additionally shaded reduce excessive heating interior. Unfortunately, shading attenuates transmission remote control systems just much emission from sun. compare advantages drawbacks infrared radio frequency systems, becomes obvious that radio frequency technology helps overcome some restrictions infrared technology. However, infrared technology other problems solved; both systems likely co-exist.
tional characteristic. This high-directional characteristic IRED frequent object customer criticism, since aiming target with accepted. looking receiver, infrared system quite simple. photodiode converts received light into current which then converted into digital signals special circuits without high-power requirement. Higher system costs result from several receiving diodes increased expense installation. costs subassemblies system, however, will always low, compared system.
System
systems operating band restricted line-of-sight coverage optical systems diffraction reflection radio waves edges conductive surfaces well their capability penetrate di-electric materials. This becomes apparent illumination space even under complicated spatial circumstances buildings. Also necessity receiver with transmitter removed because commonly used small, low-gain aerials show almost perfect omni-directional radiation pattern. range system well defined because mentioned propagation characteristic additional polarization losses. These vary from zero approximately depending relative orientation transmitter receiver antennas. Nevertheless, there high statistical probability sufficient field strength most cases. other side, problem could probability excess range, such when several conductive surfaces coincidentally located close transmitter receiver such that they form elements parabolic reflector. Wave guidance occurring along conductive planes, instance multi-storey park, increase operation range well. this case, considerable discrepancy between optical perception range user range transmission link exists. applications with higher security requirements, misuse must prevented. Listening-in radio frequencies with sensitive special receivers appears problem. Average technically-orientated criminal intelligence sufficient receive, store re-transmit data telegram without changing code. These problems were mentioned when infrared transmission links were introduced, seemed critical owing restricted range directional effect IRED.
Infrared System
Common infrared remote control systems galliumarsenide light-emitting diode transmitter which emits light 1000 wavelength. possible speak rectilinear propagation. Reflection mainly takes place visibly reflecting surfaces. Diffraction edges restricted just wavelengths therefore neglected. this reason, several receiving diodes should installed ensure correct operation under various conditions. appropriate, omni-directional receiving diode used. Operation system restricted area which user reaction. Interference caused continuous light from from headlights other vehicles, 100-Hz components mains-operated incandescent lamps their harmonics case gas-discharge lamps. Interfering light 30-kHz band from modern energy-saving lamps with switchmode power supply also considered. Spectral components data signal within these frequency bands should avoided coding. transmitter side, purpose current saving, pulse-position modulation with extremely markto-space ratio used. Operation carried single IRED (Infra Emitting Diode) with extreme direc-
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Dedicated Transistors Keyless Entry/ Remote Control
Part Number Function Features Package
Transmitter Receiver
BPV23NF TSHA520. TSHA550. U426B-FP U2535B-FP U2538B-FP driver, transmitter, constant current source, preamplifier, typical 0.26 standby current, preamplifier, typical 0.55 standby current, diode emitter family photo detector, sensitivity typical Side view T1-3/4, T1-3/4,
12_, High efficiency, 24_,
High efficiency, Low-power consumption
Adjustable constant current (0.2
Only external components required
Transmitter Receiver
BFQ67 BFR92A S822T S852T U2740B-FP U2741B U3741B U4311B U4311B-FS U4311B-FL U4314B-FP receiver, 10.7 MHz, amplifier, demodulator, logarithmic RSSI receiver, 10.7 MHz, amplifier, demodulator, inverting clamping comparator non-inverting Silicon planar transistor Broadband amplifier planar transistor, input impedance transmitter remote control transmitter remote control receiver noise, high gain noise, high gain noise, current noise, current Wide frequency range: MHz, supply voltage versions, supply voltage Full integrated part demodulator, very current consuption Low-power consumption, Low-power consumption, 105_C Low-power consumption, Low-power consumption, typical SOT23 SOT23 SOT143 SOT23 SO16 SSO16 SO20 DIP16 SSO20 (0.65) SO16L
Remote Control Encoder Transponder
U9280M-FS Microcontroller with transponder interface Transponder function with remote control encoder integrated SSO20 (0.65)
4-bit Microcontroller, Suitable Systems well Encoder Decoder
M44C260 M48C260 M44C510 M44C090/M44C890 M44C092/M44C892 M48C892 4-bit MCU, ROM, RAM, 8-bit timer, watchdog, EEPROM version M44C260 encoder, ROM, encoder, EEPROM optional encoder decoder, EEPROM optional version M44Cx9x-series qFORTH language, standby current, operating modes (For more information, please information Microcontrollers section) SSO28 (0.8) SSO20 (0.65) SSO28 (0.8) SSO20 (0.65) SSO20 (0.65) SSO20 (0.65) SSO28 (0.8)
Note: Micromodules subassemblies transmitter/receiver request.
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U2740B Transmitter Remote-Control Applications
Introduction
remote control market, TEMIC leading position since more than years. Now, TEMIC's latest remote control product, transmitter U2740B, ready increase performance transmitters more secure convenient radio systems. market applications such automotive keyless entry industrial domestic installation (garage-door opener, remote meter reading, security systems, etc.) rapidly growing. estimated that these remote control systems with power data rates kbit/s will have annual increase more than 30%. now, most transmitters SAW-(Surface Acoustic Wave filter) based, operating with modulation, batteries inaccurate output frequency. Using dedicated transmitter U2740B, customer able carry (Amplitude Shift Keying) (Frequency Shift Keying) modulation nearly same cost. This improves system performance more precise transmitter frequency better signal-to-noise ratio, resulting smaller (BitError Rate) value regarding receiver. high-quality systems with much better interference resistance, course better alternative. receiver U4311B also able handle ASKand FSK-modulated data. more information, please chapters "Components RF-based Remote Control Systems" "UHF Remote Control Systems: Receiver Front Complete Receiver Design Hints". U2740B capable being operated with only Lithium cell this even temperatures -20° Celsius. precision output frequency depends only crystal used. order help customer optimize system costs achieve simple compact design with high security level, TEMIC supports system requirements offers semiconductor devices needed (including software). members MARC4 family M44Cx9x able encode well decode standard hopping codes high-security encryption algorithms minimum energy consumption. Applications realized using TEMIC Semiconductors products able match legal prescriptions worldwide perfectly remote-control market needs.
Transmitter (e.g., key)
Receiver
cell
Encoder
Keys
transmitter U2740B receiver RF-Receiver
U4311B U3741B* U4311B
M44Cx9x
Decoder M44Cx9x
development, samples available Q1/98 Figure
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General Information
Remarks U2740B
U2740B PLL-stabilized, highly integrated ASK/FSK transmitter especially designed data rate transmissions. well suited keyless entry, home security many other remote control applications. device features very supply voltage (specified down -20°C 85°C) enable single lithium cell even very temperatures 80%-discharged lithium cell; well supply current PLL, crystal oscillator (XTO) circuits (typ. mA). high output power (+1.8 dBm) with supply current typ. entire circuit (VCO, PLL, power amplifier) makes this device cost-competitive, high-performance solution keyless entry systems. single-pin crystal oscillator integrated switch changing load capacitance crystal ideal systems enable very reproducible frequency deviation more than kHz. high output power with only current power amplifier results achievable (Effective Radiated Power, measured according 200) small keys dBm. contrast SAW-stabilized transmitters, U2740B crystal-stabilized output frequency which eases design transmitters with smaller tolerances output frequency range enables select frequencies different from those SAW-stabilized systems.
(measured with network analyzer). resulting radiated power about dBm. design transmitter board, resonant loop should cover whole area transmitter board. impedance loop antenna should transformed differential load impedance outputs ANT1/ANT2 about ZANT1,ANT2 using loop quality factor QLoop magnetic loop covering whole board, efficiency 2.7%, radiated power will reached regarding demo board. quality factor constant, efficiency loop antenna increases function (Area)1.5. impedance transformation, gamma-match method used. Experimental results carried TEMIC show that microcontroller, U2740B battery (with 3-mm distance board) fixed area surrounded resonant loop will damp quality factor below 100. Further results demonstrate that most cases, resistor necessary reduce quality factor. quality factor loop antenna must tuned. quality factor fixed values capacitors C10, used.
Remarks Battery
single CR2025 lithium cell recommended power supply U2740B transmitter. This cell capacity about mA/h Sending 20000 telegrams year duration each data transmission (with time crystal oscillator, depending crystal) will result energy consumption year. This means, that energy consumption transmitter much lower than self-discharge lithium cell. alternative battery, CR2032 lithium cell used. typical value minimum operating supply voltage -20°C guaranteed value under mentioned conditions Thus, U2740B matches specification lithium cells -20°C discharge. U2740B device standby current VAM_in which typically nanoamperes 25°C. temperature 85°C, TEMIC guarantees standby current (typical value 0.16 µA). TEMIC's M44Cx9x series processor standby current (typ. µA), resulting very standby current system. discharge battery year. With 20000 messages transmission time each current consumption, energy consumption year. This means that battery changed every years.
Remarks Demo Board
demo board, output power about with differential load impedance ZAntenna VAM_in differential input impedance loop antenna measured with network analyzer. loop antenna theoretical efficiency (-20 radiated power should about dBm. measurement radiated power demo board according showed radiated power (all spurious emissions dBm). transmission frequency demo board 433.92 load capacitors crystal designed frequency deviation. board operates with supply voltage temperature range -20°C 85°C. loop filter designed transmissions kBaud Manchester coding.
Loop Antenna Demo Board
antenna printed demo board efficiency approximately with quality factor QLoop differential impedance antenna about
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TEMIC's Demo Board
Circuit Evaluation
Figure shows schematic transmitter demo board, figure connections board. First, power supply connected between GND. Then, AM_in-, CS-, FM_in Pins should connected GND. result, board operates standby mode current consumption only nanoamperes. Next, AM_in demo board have connected demo board transmit mode consumes about
L1=18nH Toko LL2012-F18NJ C5=2.2p OSC1 TOKO KV1832C R1=2.7k C1=4.7n R3=22k R2=1.5k 4=2.7p OSC2 C2=5.6p C3=22n FMin PDout XTAL2
send FSK-modulated signals, signal generator with rectangular output frequency have connected FM_in. When connecting small whip antenna spectrum analyzer's input, radiated spectrum seen. send ASK-modulated signals, FM_in connected ground means jumper, signal generator should connected AM_in.
U2740B
ANT2
100p tenna
Vref Iref power
ANT1 XTOout C8=10n R5=2.7k
R4=10k C10,11=4.7p Vs=3V C9=1n
XTAL1 3.39MHz 4.7p
Figure Schematic demo board
AM_in
Description
operating voltage amplitude modulation input frequency modulation input lock-detect output (only when pull-up resistors added crystal oscillator output (only when pull-up resistors added) chip select input
Crystal 3.39
AM_in: FM_in: XTO:
FM_in
Figure Connections demo board
pull-up resistors R1/R5 inserted, they mounted bottom side demo board.
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Starting Transmission
U2740B starts operation. crystal oscillator starts operating with delay about dependent crystal used. Within next locks times frequency crystal. FM_in AM_in should during this time. FSK-modulated signals, AM_in should connected after output modulated using FM_in DATA input. ASK-modulated signals, FM_in should connected GND. AM_in should used DATA input. best start data transmission wait until first negative falling edge appears lock detect output. Then, locks within next Settling time about depending crystal.
Development Customer-Specific Board
When designing customer-specific solution with U2740B remote control transmitter, design hints given below will help solve arising problems. following paragraphs describe design customerspecific VCO-LC tank, different crystals, dimensioning passive filter frequency control loop. most difficult part regarding design very small transmitter layout, especially layout magnetic loop antenna. Therefore, detailed design hints development layout well equations calculation customer-specific solution's given. Regarding demo board, result equations value according measured absorber chamber exactly same.
Modulation
equivalent circuit AM_in (Pin (±20%) resistor diode series. current power amplifier controlled level current flow into modulation bandwidth MHz. current into AM_in 0.75 (0.5 typ.). AM_in, blocking capacitor necessary. This, however, reduces usable bandwidth modulation about MHz.
Customer-Specific Modifications TEMIC's Board
Using Different Crystals
crystals demo board have size about 11.35 (width/ length/ deepness). Such HC49S crystals well suited small transmitters such keys represent most costeffective solution available. crystals demo board obtained from Data Module Germany. They have stability 25°C temperature stability ppm. ageing first year. resulting center frequency tolerance kHz. crystals needed, Data Modul also offer them small XK-1 packages. case using different crystals, values capacitors have changed that frequency deviation nominal center frequency 433.92 MHz. This achieved changing capacitor with voltage FM_in until output frequency about 433.95 MHz. capacitor with voltage FM_in adjusted until output frequency reaches 433.89 MHz. crystal used must have series resonance resistance case external crystal oscillator chosen, used connect this oscillator. operate when CMOS voltages applied, peak-to-peak voltage ~100 should used. achieve this value, voltage divider with resistors used. peak-to-peak voltage then coupled with capacitor
Modulation
FSK-modulate output, output power must constant value. supply voltage used, supply voltage directly switched AM_in Pin. supply voltage further resistor added such that nominal current into AM_in When voltage FM_in capacitor switched parallel Thus, crystal operates frequency which less than case switch being closed (depending values C6/C7) output frequency FSK-modulated. 433-MHz operation, frequency shift lower shift possible when values chosen capacitor smaller). This frequency shift very stable within given temperature range mass production.
Supply Voltage
temperature -20°C, supply voltage necessary proper operation. 25°C, this 70°C, (see "Remarks Battery"). These values appropriate single lithium cell voltage supply.
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Different Design
U2740B digital phase/ frequency detector with charge-pump output. must designed that control voltage sufficient trim output frequency 433.92 MHz. When using different inductors varicaps demo board, small loop might added near loop antenna couple output power frequency counter. achieve better coupling between loops, short might placed loop antenna's instead resistor 433-MHz operation, following values must chosen: capacity range capacitance diode must selected that control voltage will generate output frequency MHz. control voltage will generate output frequency MHz. resulting value KVCO voltagecontrolled oscillator used design loop filter with
Different Values Loop Filter
achieve best performance transmitter PLL, loop filter must matched baudrate customer-specific system. This considered case FSK, especially spurious emissions importance. following equations determine values resulting damping frequency control loop. TEMIC's demo board, following valid: using FM-demodulation option spectrum analyzer, effect loop filter output signal seen. fVCO transmitter frequency (433.92 MHz) fVCO divided phase comparator frequency, (512) output current phase comparator constant MHz/V) max.Data
KVCO Switch Loop
Loop
Switch
Loop
demo board being designed TEMIC, KVCO MHz/V. customer-specific design, tolerances temperature dependencies this resonator have result control voltage dimensions layout should match those given demo board. this case, value customer-designed board modified. variation range wide enough frequency high, higher value added capacitor parallel with necessary. proper operation within specific temperature range mass production, resonant impedance tank must inductor with varicap with series resistance therefore recommended operation. Problems occur when loop antenna strong coupling tank VCO. Therefore, tank should placed area surrounded resonant loop. contrast, other components small transmitter placed there achieve area large-sized possible loop antenna. Other problems occur when modulation control lines (lines from AM_in FM_in) have coupling distortion tank VCO. TELEFUNKEN Semiconductors 08.97
-tan(p cos(p
Loop
Loop
Loop
Loop Loop
switching time, TSwitch, between output frequencies depends transmission code baudrate. Manchester coding Switch
baudrate baudrate
Non-return-to-zero coding Switch
values have exactly ones given calculations. designer select values from series being close possible given ones. Example: Transmission with Manchester coding kBaud kBaud non-return-to-zero coding: Switch
Development Board
When designing small transmitter, board layout very important aspect. layout design carried with special care. transmitter board optimized, functioning U2740B optimum radiated power might below maximum achievable value. easiest match impedance loop antenna output U2740B gamma match (similar functioning resonance transformer with capacitors) demo board. Doing also fastest method design board. Please note: carefully designed layout enables omit tuning points transmitter!!
75.3 23.2 4.26 20.63 1.55
Loop Loop
Placing U2740B-Relevant Parts
resonant loop antenna demo board circle with diameter) should cover area transmitter layout large-sized possible (for restrictions, please "Different Design") should placed opposite side U2740B. skin-effect losses, width resonant loop wire must resonant loop shall surround VCO-LC tank because strong coupling between resonant loop tank cause problems. increased detune resonant loop, capacitors C10/C11 resistor should possible from user's hands. means resistor quality factor loop antenna determined value. using np0-capacitors with ±5%, quality factor about dimensioned. choose value resistor inductance length resonant loop have calculated. This value loop inductance also used estimate values capacitors C10, C11. values C10, their turn necessary determine tuning range tuneable capacitor used C10, design phase. supply voltage should connected resonant loop opposite side C10, C11, impedance resonant loop transformed value being optimum load impedance power amplifier U2740B. this, connection line connecting ANT1/ANT2 resonant loop placed opposite side board. move connection point, connection lines prolonged. first layout, there feedthrough holes, various positions them have tested. This done drilling various holes into board, feeding through wire soldering upper- bottom side board. best position feed-through holes might used second layout version. must tuned maximum every feed-through position. TELEFUNKEN Semiconductors 08.97
following values chosen:
Spurious Emission
phase-comparator frequency (for 433-MHz system), U2740B able reach spurious emission values even 10-kHz loop bandwidth frequency control loop. Such values, however, achieved only case good blocking (Pin 11), AM_in (Pin FM_in (Pin well supply voltage pins. spurious performance considered critical parameter (e.g., transmitters with effective radiated power dBm), blocking circuits necessary meet values prescribed law. this case, possible only 100-pF blocking capacitor between Pins home security applications with substantially higher antenna efficiency whip antennas radiated power dBm, spurious emissions necessary meet values prescribed law. this case, blocking circuits well layout with only slight coupling between output Pins ANT1/ANT2 AM_in FM_in Pins necessary.
When designing second layout, various values have tested until maximum radiated power reached. achieve optimum tolerance performance, similar values should used. should np0-type capacitors with tolerance case tolerances significantly less than higher value quality factor, used. U2740B's outputs ANT1 (Pin ANT2 (Pin 14), differential load impedance should differential output capacitance output should used differentially. This recommended differential output being used single-ended output power which less than being used differentially. differential mode also suppresses second harmonic that conditions regarding radiated power second harmonic prescribed met.
Loop
inductance resonant loop length wire forming resonant loop
LLoop
achieve reproducible values power radiation mass production, quality factor resonant loop should chosen according
tolerance capacitors used (C10, C11)
DC/C
Placing Remaining Parts
high-frequency part board operates well, remaining board area inside resonant loop used place microcontroller, switch, battery etc. These components placed (esp. battery) cause decrease resonant loop's quality factor. possible, space between battery loop antenna should most cases, value must increased achieve same power radiation without additional components resonant loop.
tolerance capacitors used 2.5%, length coefficient within chosen temperature range board material must considered well, resulting change DLLoop/LLoop added DC/C. temperature coefficient capacitors typically ppm/K. effect temperature capacitor neglected most cases. Calculation resistor
Loop
Calculation loop antenna's efficiency:
Loop
Performance Calculation Magnetic Loop Antenna
transformation impedance output U2740B operates well, efficiency loop antenna thus power radiation calculated. Both operations carried following way: differential input impedance loop antenna demo board measured power flowing into loop antenna calculated. Next, efficiency loop antennna calculated with equations given below. Thus, possible estimate radiated power. measurement radiated power carried TEMIC according resulted exactly same value radiated power (with neglectable deviation dB), i.e., Str. RStr.
radiation resistance function resulting loop inductance approximately function A0.5, efficiency loop antenna with constant quality factor function A1.5. 1.5)
increase covered area times results increase effective radiated power (typ.). efficiency typical loop antennas used keys (without trimming point) within range (-20 (-15.3 dB), depending size. With tuning point, typical qulaity factor used, resulting efficiency increase 2.3% (-16.4 6.8% (-11.6 dB). loop-antenna size major design aim, stray capacitances will smallest value loop capacitor value about using capacitor, trimming capacitor series quality factor 150, maximum possible efficiency value, i.e., about dB), achieved. this kind loop antennna, area about each antenna must tuned.
radiation resistance resonant loop antenna area inside loop antenna wavelength frequency
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wire's width small, skin-effect losses resonant loop lead reduction loop antenna's quality factor. easiest calculate skin losses square resistance copper wire 433.92 (Rsquare mW/square approx.). copper wire's surface should have plate this increases series resistance. series resistance, resonant loop calculated follows: square width wire used length resonant loop wire
maximum possible quality factor with
given:
Loop
most cases, this quality factor much higher than 500. quality factor capacitor used determines maximum possible quality factor loop antennna.
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Appendix
Demo Board Schematic
TOKD LL2012 FI8NJ
OSC1 OSC2 AMin PAGND
St1/5 AMin
TOKO KV1832C St2/3 St2/4
Loop antenna ANT2 ANT1
2.7k .10k
U2740B
XTOout 3.39 XTAL2 XTAL1
C10, C11= 2.7k .10k St1/6
St2/2 FMin
FMin PDout
St2/7 St2/5
St1/1 St1/2 St1/3 St1/4
St2/1 St2/6
13345
Demo Board Component Placement
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TEMIC U2740
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Component List
Components 2-kBaud Manchester coding Varicap TOKO LL2012-F18NJ
TOKO KV1832C Rank alternative Toshiba 1SV276, this needs, however, different design)
3.3900 ppm, -10°C 70°C from DATA MODUL Germany
Crystal:
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Appendix
case customer intends apply different methodology adjust loop antenna, information given Appendix read carefully before starting design. transistors Q1/Q2 designed maximum current Therefore, current into AM_in must supply voltage series resistor connected AM_in should used (e.g., supply voltage series resistor kW).
Output Stage U2740B
shown figure U2740B's output stage consists open collector transistors, differential pair connection. output current, IOut, switched from vice versa. This output current seven times current flowing into AM_in Pin. output-stage driver designed that driving power sufficient switching from (and vice versa) within range MHz. voltage swing this output limited peak each collector because chosen circuit arrangement. differential peak-to-peak output current differential load impedance differential output voltage swing peakto-peak. Calculation output power:
Single-Ended U2740B's Output Stage
Sometimes, might necessary employing U2740B's output drive whip antenna. this purpose, however, recommend balun transformer, U2740B's output single-ended configuration instead. this, outputs have connected power supply, other LC-impedance transformer network. Figure shows possible arrangement. output voltage swing ANT2 limited peak-to-peak current peak-to-peak. single-ended load impedance should using this value, output power 0.75 (-1.25 dBm) will delivered. network transforms load impedance into value needed U2740B's output stage (i.e., Please note that realization layout, some modifications regarding values transformer network might become necessary stray inductances capacitances board.
out,
out,
dBm)
Vout, peak-to-peak output voltage Iout, peak-to-peak output current
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ANT1
ANT2
AM_in
PAGND IOut Figure Power output stage U2740B
ANT1 ANT2
AM_in
IOut
PAGND
Figure Single-ended output 433.92
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Components RF-Based Remote-Control Systems
U4313B which mentioned several positions this report dedicated designs. described applications U4311B appropriate way.
Transmission Frequencies Systems
(Citizen Band) 224.5 (Microwave Ovens) (GB) 433.9 (D,EC) 315/433.9 (USA) SAT-TV EUROPE SAT-TV SAT-TV
13.5
SW-Radio AM-Radio
FM-Radio
Figure Chart frequencies
radio-frequency-based remote control system designed, first decisions choice operation frequency. frequency bands that utilized RF-based remote control systems were fixed national authorities therefore they vary different countries. Nevertheless, most countries similar frequency allocations remote control systems exist: short-wave band ("citizen band" MHz), band (300 MHz), band around GHz. chart frequencies given figure
divided into channels most countries, expense filtering must high. great disadvantage large number public services this band, that rather crowded. avoid distortions from high-power transmitters, good large-signal behavior high selectivity required. band makes rather small antennas possible. Especially small loop antenna transmitter side included miniaturized PCB. behaves spot radiator, quasi isotropic transmitting characteristic provided. Wave propagation rectilinear first approach, receiving "round corner" possible deflection metallized edges. wave propagation along conductive surfaces helps overcome larger distances, example parking garages. production, conventional techniques applied using discrete active components with high gain power-loss. Advantageously, they Surface-Mounted Devices (SMDs), like passive components, too. These parts available many variations thanks telecom mass production. layout much more critical than short wave band, especially miniaturized solutions required. fact, layout treated component requires experience production subassemblies.
first short-wave band will considered. advantage these frequencies larger operation distance that obtained with certain transmitter power, efficiency active components better than higher bands. layout Printed Circuit Board (PCB) less critical, because parasitic capacitors small compared used components unwanted coupling easily avoided. Unfortunately, required antenna size largest possible frequency bands. relationship between antenna size, operation frequency received power fixed distance discussed chapter "Appendix". radiation characteristic transmitter antenna isotropic, therefore operation range depends antenna's orientation. frequency range
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Finally look 2.4-GHz band. this frequency range given transmitter power, operation range shorter compared band. reasons higher free-space losses poorer efficiency active components. absorption water molecules, these frequencies injurious health operation distance reduced rain. production subassemblies this band requires special techniques, components expensive degree integration very small. With regard efficiency, this frequency range suitable lowcurrent applications. advantage 2.4-GHz band possibility transmitting high data rates thanks larger bandwidth available. conclusion small-sized, universal, low-power remote control links, range seems best choice. following chapters, only applications this frequency band will discussed, although receiver applied transmission links working other frequencies too.
Further Boundary Conditions
decision made towards radio frequency based remote control system 433.92 MHz, legal prescriptions only part boundary conditions. Other boundary conditions depend desired application. automotive field, stringent requirements manufacturers have met: average current consumption every additional module built into must exceed Additionally, maximum case size transmitter receiver, required operation distance, temperature humidity range, EMI, well shock protection reaction time examples boundary conditions. location antenna subassemblies could also cause difficulties. technical attributes, such transmitter power receiver sensitivity, modulation system coding techniques derived from boundary conditions. Most these aspects interdependent some them discussed subsequent explanations.
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System Comparison Remote Control Concepts
Control inputs
Encoder
transmitter
Antenna
Transmitter module
Antenna
tuner
amplifier demodulator
Data filter comparator
Decoder Control outputs
Receiver module Receiver module
Figure Block diagram remote control system
engineer designing RF-based remote control system choose between various concepts which described subsequent chapters. order gain overview, block diagram figure simplify matters, uni-directional transmission system considered. Therefore, only transmitter single receiver needed. Nevertheless, most following considerations apply also multi-directional systems. Both transmitter receiver subdivided into digital analog section. digital part transmitter encodes information serial stream which modulated upon carrier. This done transmitter unit. Vice versa receiver module, serial data signal recovered subsequent decoder makes transmitted information available control outputs.
More complex require higher supply currents, lower average supply current obtained standby polling concepts, which explained subsequently. standby concept minimizes current consumption receiver utilizing fact that some functions permanently required. Therefore, receiver modes exist. First standby mode, only those parts turned which needed detect presence relevant signal, necessary switch receiver active mode. this second mode, remaining components, which needed further signal processing, enabled current consumption consequently increased. advantage this concept short reaction time. soon input level exceeds "wake-up level", switching carried virtually without time delay. ensure that receiver does permanently remain active mode, wake threshold above limiting sensitivity active mode. This disadvantage because profit receiver's absolute sensitivity. other side, taken into account that decoder, permanently receiving random sequence will sometimes detect valid telegram. statistic probability such event, caused noise, interference similar signals increases with frequency duration times when receiver active mode. wake-up concept therefore helps reduce redundancy transmitted code.
Standby versus Polling Concept
some applications such those automotive market, low-current consumption most important demands receiver side. meeting this demand using low-current, permanently receiving amplification demodulation, combined with front that stacked with integrated circuit. those applications, receiver U4314B with total current consumption below provided TEMIC. This integrated circuit discussed this paper. data sheet available further informationis required.
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polling concept, switching receiver between sleep mode active mode externally controlled. low-current microcontroller switches receiver periodically short time active mode looks occurrence valid data. such data detected, microcontroller causes receiver remain active mode until complete data telegram received more valid data packets received defined time. this reason, active time long enough decide whether signal contains valid data. Obviously, benefit polling mode better sensitivity, because separate wake-up level needed beyond receiver's active mode limiting sensitivity. drawback this concept longer reaction time which depends switching rate. duty cycle between sleep times active times determined required average supply current, active times reduced desired value, reaction time longer principle. Summarized, decision these concepts depends degree importance reaction time sensitivity. TEMIC provides receiver covering both conceptions.
same frequency primarily used here well. harmonics VHF-range television transmitters, mobile phone network and, slightly apart, television band close 433.92 MHz. These potential sources interference seem critical compared influences remote controller short wave range instance expect. Nevertheless, high selectivity required. Radiation receiver appear local oscillator's frequency, which located 10.7 beside input frequency. easily suppressed preamplifier input filter. 10.7 chosen well-used technology, low-cost components from radio production available with many different specifications. receiver take over signal processing until data output, operational amplifier clamping comparator included base-band filtering data shaping. U4311B U4313B suited well demodulation. drawback superheterodyne concept comparatively high expense, fortunately whole processing from input data output managed integrated circuit TEMIC. Image frequency reception typical shortcoming superheterodyne receiver, this case, reception frequency 423.22 minus 10.7 MHz. achieve good image rejection, bandwidth input filter preamplifier narrow enough. requirements regarding receiver radiation strict, superheterodyne receiver only possible concept. superregenerative receiver more simple subsequently cheaper than superheterodyne receiver. superregenerative concept does intermediate frequency. modulated directly converted base band means periodically oscillating transistor stage. oscillation frequency same received frequency, radiation receiver reduced simple input filter. selectivity, this, rejection against band interferences worse because there additional filtering like superheterodyne's band. Another drawback mediocre large-signal behavior. Especially low-current concepts, oscillations receiver transistor intermitted strong input signal. Using amplitude modulated systems, data transmission commonly applied with modulation depth 100%, rise time receiver limits data rate kBaud.
Superheterodyne Superregenerative Receiver
integrated circuits U4311B U4313B support superheterodyne receiver concept with average current consumption approximately special device U4314B, which supports receiver with total supply current below front those receiver concepts typically consists input filter, preamplifier stages, local oscillator mixer stage. oscillator mixer combined single stage. front converts modulated down Intermediate Frequency (IF) 10.7 which passes filter supplied receiver Technical details discussed following chapters. superheterodyne concept well-known from radio receivers, where proved good performance with regard sensitivity, selectivity large-signal behavior. Radio specialists technically informed radio listeners aware image frequency reception cross modulation. These aspects also significant remote control receiver. practice, field strength required interference expected only proximity strong transmitters, they will then restrict system range. Amateur radio must taken into account frequency 433.92 because
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summarize, superregenerative receiver cheap alternative data rates low-performance applications. legal prescriptions regarding receiver radiation have fulfilled. other applications with higher requirements system's performance operation, superheterodyne concept superior. narrow-band operation, prescribed France, solution without alternative.
advantageous apply special coding technique with mark-to-space ratio shifted close one. Amplitude modulation does work noise suppressive, therefore interferences stronger compared system. This effect known every radio listener audible difference between medium wave reception. operation enables higher transmission rates shorter transient times. Therefore, operation better choice semi-duplex transmission. open future developments, which will probably require higher data rates. transmitter works maximum power during whole transmission that average output power higher compared transmitters. continuous transmission further gives better compatibility with existing infrared systems, that same coding used. Frequency modulation exploits system's bandwidth much better than amplitude modulation, therefore able reduce interference, modulation index herewith also bandwidth matched. However, easy achieve high frequency deviation with rather simple, SAW-based transmitters. benefit TEMIC's concept additional expense versus receiver: only discriminator filter resistors have added.
Comparison Operation
remote control link with superheterodyne receiver offers possibility using amplitude modulation well frequency modulation. operation more simple realize, especially with regard transmitter design. achievable sensitivity referred certain error rate TEMIC system comparable operation with small frequency deviation.
most simple solutions sometimes have drawbacks. cheap single-stage transmitter used, obtainable data rate limited kBaud. This fact results from comparable long transient time transmitter, when completely turned off. However, several applications, such keyless entry systems instance, these kinds transmission rates sufficient. achieve high average transmitter output power,
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TEMIC Receiver U4311B, U4313B, U4314B
more detailed description remote control system, figure once more. first, receiver part will discussed. U431xB family essential components, their main features listed below. common features. integrated circuits U4311B U4313B include following functions:
Wide supply voltage range Suitable battery operation operation mode (U4314B only Low-current consumption standbyor polling concept (with U4314B total current consumption below tional amplifier clamping comparator data filtering shaping included
amplifier Logarithmic demodulator demodulator Wake circuit with mono-flop Operational amplifier Data comparator, non-inverting type U4311B, inverting type U4313B
With exception U4314B, high-performance operaA short description these integrated circuits given subsequently, table shows survey their different
Voltage regulator
only difference between these polarity data output. U4314B receiver without baseband processing. technical data further information concerning receiver ICs, please consult data sheets.
Table Survey remote control receiver U4311B, U4313B, U4314B
Common Features Wide supply voltage range: amplifier, U4311B, U4313B including operational amplifier realize data filter clamping comparator data shaping, with serial data output external data processing Stabilized reference voltage externally available Quiescent current approximately
Differences Feature 16-pin package 8-pin package Included wake-up circuit switches active mode case sufficient input level externally applied control signal (additional polling) Permanent receiving with total supply current below Inverting clamping comparator Non-inverting clamping comparator operation RSSI output operation U4311B U4313B U4314B
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following explanations receiver's part, please assume that U4313B being used. principle, this information transferred also other ICs. block diagram, showing IC's internal parts external components complete receiver shown figure 10.7-MHz signal from front passes integrated amplifier, which operates amplitude- frequency-modulated signals either logarithmic demodulator quadrature detector logarithmic demodulator implemented avoid settling time problems effected amplifier with automatic gain control section. data shaping filter advantageously realized with internal high performance operational amplifier reduces system bandwidth optimized compromise regarding noise reduction data rate. Thus optimal error rate achieved without further additional active components. brief description various data filter designs follows chapter "Data Filter Data Regeneration".
Received Signal Strength Indicator (RSSI) activated. level signal increases, whole circuitry turned wake-up circuit. This signal externally available which switches level active mode. wake output supplied with open collector, high level depends voltage which connected. Therefore, this output suitable switch external components like microcontroller applying control signal with standard level. After adjustable hold time, determined wake time constant integrated circuit rests down sleep mode. this case, supply current required. external resistor matched ground blocks wake circuit gives full function lower level, supply current increases typically output signal operational amplifier input inverting comparator. time constants adjustable must adapted transmission code data rate. time constant should large, compared data rate optimized noise- suppression. difference peak values controls hysteresis, their mean value used comparator threshold. This clamping comparator works data regenerator. subsequent chapter, results DC-based dynamic measurements receiver presented discussed. These explanation complete deepen measurement results given data sheets.
Mode control input
comparator connected output filter level-dependent hysteresis clamps reference voltage signal minimum maximum peaks described later. Without input signal sleep mode beside bandgap reference wake circuit, only amplifier demodulator which operates
Wake-up output
Inverting clamping comparator Wake
Data output Control outputs Microcontroller M43C200 M44C260 M44C892
VRef 433.92 resonator 423.22
Bandgap Internal VRef level Quadratur detector Wake-up circuit
Front S822T/ S852T
10.7 Ceramical filter RSSI output 10.7 ceramical tuned filter output Data filter amplifier Operational amplifier EEPROM
from output
Figure Block diagram receiver U4313B
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Parameters Receiver
order carry measurements receiver testing adapting certain applications, printed circuit board available. This contains complete signal processing from input data output. circuit diagrams given figures respectively figures applications U4311B/ U4313B. placement components found figures figures Figure shows layout universal PCB. These circuit diagrams represent actual application circuits. marked otherwise, statements component numbers referred these test circuits. component values application-minded deviate from those circuits published data sheets. principle measurement setup given figure showing external connections board measurement equipment. data generator level shifter necessary measurements which discussed within this chapter. electrical characteristics integrated circuits nearly independent supply voltage, internal functional blocks referred bandgap stabilized voltage. This applies also supply current figure which shows typical dependence supply current from supply voltage U4313B.
Supply current (mA) Supply voltage Standby mode Active mode
Figure Supply current U4313B supply voltage
Data audio frequency generator output
Power supply
Voltmeter
input Level shifter (optional) output
Amperemeter
Modulation input Signal generator output
Power supply Comparator output Data Data filter output input Wake-up switch
Circuit entirely turned
test board
output (Pin output (Pin Field strength output Wake-up output Amperemeter
Wake-up function
Figure Setup measurement parameters
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Switching between passive active mode controlled wake-up switch, with input test board disconnected, that signal generator necessary. Another possibility apply unmodulated signal with levels above below wake-up threshold, while wake switch "wake-up function"- position. output voltage power supply shifted from cover whole supply voltage range. this measurement, amperemeter shown figure disconnected, otherwise current output would increase total supply current. receiver U4311B U4313B provide internal wake-up circuit with fixed threshold. wake threshold receiver ICs, that means required level switching from sleep mode active mode, almost independent supply voltage temperature. variation supply voltage over total range from causes variation wake threshold less than This means that sensitivity receiver nearly independent supply voltage. input integrated circuit family U431xB provides input impedance approximately match directly ceramic filter, resistors needed transformation 50-W input resistance test board. voltage loss caused this circuitry calculated follows:
increased current consumption used criterion being active mode. Another criterion logical state wake output. high level indicates sleep mode, consequently active mode marked level. wake output supplied with open collector, high level depends voltage which connected.
Frequency Response
parameters receiver include measurements signal-to-noise ratios, demodulator characteristics frequency response data filter error rate measurements. these subjects will discussed separate chapters. Within this section will merely have look frequency response amplifier. possible transmission systems signal processed same amplifier, characteristic influences applications. amplifier works without gain control circuit.
Output current (mA) dBmV dBmV frequency (MHz) dBmV dBmV
With actual values resistors, loss approximately -5.6 voltage level dBµV IC's input corresponds voltage level 45.6 dBµV input test board with this also output signal generator. level measured either directly IC's input with millivoltmeter spectrum analyzer, measurement referred input test circuit which will method further measurements published within this paper. Please confound these different values with each other.
Figure Frequency response amplifier
measurement configuration according figure used. frequency unmodulated signal generator swept, applying various levels test board. current from output ground measured with amperemeter while data filter decoupled. diagram figure shows level depending internal characteristic receiver ICs. seen, amplifier broadband type with slight band pass characteristic.
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Data Filter Data Regeneration
Another subject, which concerns well operation, base band filter data regeneration. optimal matching data filter used code great influence system performance, e.g., achievable operation distance. Therefore, following chapter completely dedicated this item, based profound investigations different filter types. following design hints give some assistance, using implemented operational amplifier U4311B U4313B active data filter. order minimize distortions caused filter's settling time, Bessel- Butterworth type filter proposed. bandwidth data filter should kept possible obtain noise output. Transmission rates about kBaud kBaud seem adequate many applications, case 0-1-0-1 sequence this corresponds frequency kHz. Therefore, cut-off frequency sufficient lowpass filters second order discussed subsequently. DC-coupled filter operation according figure transient time measured. This means, that data signal transmitted permanently, there will appear valid telegrams receiver's data output after receiver switched active mode. Only very first received active mode might undefined high-bit. transient time corresponding filter mode according figure approximately transient times much longer AC-coupled filters dependent coupling capacitor voltage gain between DC-coupled filter recommended polling concepts. figure filter transient time, wake time constant minimum value removing capacitor
General
types filters were investigated. first AC-coupled therefore recommended Manchester code, that means code free component. second filter quasi DC-coupled demodulator's output stage provides advantages, coding with significant component chosen. example code with long start burst, usually applied transmission AM-systems. "Start burst" means impulse beginning data transmission, which much longer than data bits. mixed with "start bit", which marks beginning data telegram. case such coding, value filter's coupling capacitor increases. Especially operation, electrolyte capacitors used, because polarity depends tolerance frequency (above below center frequency 10.7 MHz) instantaneous value data signal. avoid higher costs bigger size large capacitor, recommend quasi DC-coupled data filter. Thereby, same frequency response obtained with smaller capacitors. Both filters achieve same results input sensitivity given maximum Error Rate (BER), will shown later figures applications using polling mode most important parameters reaction time, because determines timing polling, that means minimum active time. this reason, transient time board examined. quasi
order achieve well-defined operating point circuit, operational amplifier directly DCcoupled respectively output, various bias voltages corresponding pins. this reason additional high-pass filter characteristic implemented. voltage gain filter should range demodulator's output voltage comparably large nearly independent input level. optimum value voltage gain depends gradient characteristic. systems, recommended because input levels, gradient characteristic therefore also demodulator's output voltage swing very small. value demodulator's output voltage depends R11. dimensioning filter's voltage gain been optimized practical examinations. high gain bandwidth product internal operational amplifier, treated ideal data rates several kBaud. input impedance data filter determined resistance FMrespectively output. calculations, internal output resistance well external resistors have considered. demodulator current source, therefore only external resistors significant; impedance output According test circuits figure total resistance approximately operation, according figure less sensitive against unwanted feedback, inverting filter chosen. designing active Bessel type, data filter, programs filter handbooks used. dimension active second-order Bessel type lowpass filter used test circuits, following formulas helpful, according reference [1]:
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1.362
0.618
these formulas, signifies (negative) voltage gain lowpass filter, cut-off frequency, output impedance demodulator, arbitrary value. Data filter comparator time constants design custom specific, matched data telegram. TEMIC recommends carrying dimensioning filter comparator components using test signals. this purpose, test board used. important criterion sensitivity given maximum error rate (BER), described chapter "Bit Error Rate Measurement". Depending mark-to-space ratio coding, best results obtained with different values R12, that clamping comparator gets asymmetric characteristic. receiver U4311B U4313B similar with exception data output polarity. U4311B includes non-inverting U4313B inverting clamping comparator. Therefore, operational amplifier used either non-inverting inverting filter without need more components. Furthermore, optimal adaptation microcontroller input polarity does require additional expense.
0.01
Figure Frequency response 2-kHz Bessel lowpass data filters with AC-coupling
frequency response data filter influence coupling capacitor drawn figure Obviously codes with long start burst, value increases. filter rise time mentioned before between typically. Therefore, quasi DC-coupled filter should preferred. Nevertheless, AC-coupled filter suitable smaller filter bandwidths realization filters with real band pass characteristic (for example substitution resistors capacitors). Those filters might used especially Manchester codes with higher baudrates, kBaud more. more broadband filter with small cut-off frequency would noticeably increase noise.
Quasi DC-Coupled Data Filter
conventional transmission systems, start burst necessary control receiver gain (AGC) during full transmitter output power. TEMIC system, such start burst needed wide dynamic range amplifier logarithmic demodulator respectively signal limiting mode. Nevertheless, start burst used assure compatibility with existing transmission schemes, e.g., former systems. wake concept used, start burst fill wake time receiver. those applications polling method, recommend quasi DC-coupled filter. principle circuit diagram given figure complete diagram values components shown figures filter optimized codes with long start bursts transmission rate kBaud kBaud. main difference connection operational amplifier's non-inverting input demodulator output means link.
AC-Coupled Data Filter
most simple achieve additional high pass characteristic AC-coupling between demodulator filter. following example dimensioning, data filter comparator's time constants have been optimized Manchester code with long start burst about transmission rate kBaud kBaud. high-end cut-off frequency filter kHz, voltage gain filter matched demodulator output resistance position numbers components correspond test circuits figures
0.47 Frequency (kHz)
V/Vmax (dB)
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Input (from demodulator)
limited same range means resistors R16.
Output
comparator)
Figure Principle circuit diagram quasi DC-coupled data filter
0.01
cut-off frequency determined time constant this link. impedance non-inverting input high, large resistor coupled with small capacitor nevertheless very cut-off frequency achieved. remaining filter network same type ACcoupled one. order achieve well-defined mean operating point, resistors used. These resistors ensure that offset voltage between inverting non-inverting input operational amplifier limited. operation, operational amplifier's common mode input voltage range additionally output voltage
Figure Frequency response lowpass data filters with quasi DC-coupling
frequency response examples quasi DCcoupled data filters shown figure According circuit diagrams, figures 2-kHz lowpass filter mode 4-kHz lowpass filter mode chosen. rise time part mode typically mode approximately seen, cut-off frequency below voltage gain operation
Data audio frequency generator output
Power supply
input Level shifter (optional) output
Modulation input Signal generator output
Power supply Comparator output Data Data filter output input Wake-up switch
Circuit entirely turned
test board
output (Pin output (Pin Field strength output Wake-up output
Wake-up function
Figure Setup measurement data filter's frequency response
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Frequency (kHz)
meter
V/Vmax (dB)
measurement setup evaluate data filter's frequency response seen figure Dependent type signal generator, level shifter necessary adapt audio frequency generator modulation input signal generator, that desired modulation depth respectively frequency deviation achieved. ensured, that carrier output power constant kinds modulations, that means, modulator must clamped "highlevel" modulation signal (same conditions TV-signal transmission example). audio frequency generator produces sine wave, which swept from kHz. voltage level (RMS) signal measured data filter output. Modulation depth deviation should value respectively avoid clipping effects limited dynamic range operational amplifier. measurements input level dBµV chosen. Please notice that data transmission, dynamic range operational amplifier without effect, subsequent clamping comparator used data shaping.
generator. Figure shows measurement setup. oscilloscope will display some kind "eyes", which result temporal superposition different sequences data filter's output. This signal which must converted digital stream comparator. picture scope screen with pattern system seen figure With pattern, assess signal quality, which gives basic information about amplitude- phase response system. Most important open area eye. horizontal width characterizes critical moment sampling vertical size criterion uncertainty sampled amplitude. optimal area decision, whether certain high located middle opening. long completely closed, there chance data regeneration means comparator. rather simple optimizing certain parts transmission system tuning maximum opening desired threshold sensitivity. results watched simultaneously scope screen, this method well-suited fine adjustment components. Figure shows measurement input level dBµV which corresponds wake-up threshold receiver. that almost perfect open. Therefore, signal quality very good. complete baseband signal processing functions DC-coupled, optimal threshold binary decision element mean value low- high bits' amplitude. This applies long interference present. AC-coupled system, particular transmission many successive equal bits leads so-called baseline wandering decision element, what means that optimal threshold shifts. amount this baseline wandering depends low-end cut-off frequency proportion ratio data rate number successive equal bits. Therefore, simple 0-1-0-1 sequence test signal does reveal real performance system.
Pattern
already mentioned previously, data filter matched used data coding. Therefore, certain criteria needed decide whether data filter been optimized successfully. methods well-suited this purpose: analysis pattern measurement error rate. first method will discussed within this chapter, second method explained thereafter. first familiar with expression "eye pattern". random sequence bits applied input transmission channel that band-limited, data output systems would rectangular shape. case, input that board, output signal appears data filter output. course this method also suitable test complete transmission link. oscilloscope connected system's output, while triggered clock pulse data
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Data generator Clock Data output
Oscilloscope External trigger Y-trigger input
input Level shifter (optional) output
Power supply
Modulation input Signal generator output
Power supply Comparator output Data Data filter output input Wake-up switch
Circuit entirely turned
test board
output (Pin output (Pin Field strength output Wake-up output
Wake-up function
Figure Setup examination pattern
this reason, usually Pseudo Random Sequence (PRS) used data signal pattern measurements. This sequence given length 2n-1 bits which transmitted periodically. Such pseudo random sequences generated means backcoupled shift register. distribution bits sequence quasi random maximum number successive equal bits probability occurrence lowand high almost equal never identical, because sequence number bits. largest number successive equal bits identical with exponent formula 2n-1 determining length sequence. longer PRS, more spectrum extends lower frequencies. length must therefore chosen according maximum number successive equal bits which expected real used data signal. certain coding tested, encoded before applying transmission system.
Figure pattern remote control system, data rate kBaud
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Data generator Clock Data output
Oscilloscope External trigger Y-trigger input
Counter
input Level shifter (optional) output
Power supply
Modulation input Signal generator output
Power supply Comparator output Data Data filter output input Wake-up switch
Circuit entirely turned
test board
output (Pin output (Pin Field strength output Wake-up output
Wake-up function
Figure Setup measurements
Error Rate Measurements
Another possibility judge quality transmission link measure Error Rate (BER). indicates probability wrong output receiver. systems with limited bandwidth (what applies every real system), depends transmitted stream. systems with bandpass characteristics, only data rate limited system's high-end cut-off frequency, also low-frequency cut-off important. latter limits maximum number successive equal bits. Therefore, also when measurements being made, pseudorandom sequence recommended. measurement setup given figure original data signal clock pulses applied measuring instrument, together with received data from comparator output test board. measuring instrument compares transmitted received data certain decision times that derived from clock pulse. this purpose, transmitted data clock pulse time-delayed inside measurement unit, that they fitting received data. bits which compared
equal, measurement unit generates impulse error output, which applied counter. error rate, calculated from number errors, transmission rate, counter's gate time, follows:
Alternatively, second counter clock output used determine number transmitted bits. Then calculated simple division number errors number transmitted bits. small disadvantage introduced method measurements that does reproduce conditions reality exactly. real transmission system derive clock pulse decision time from received signal. This will increase real compared measurement setup where clock signal applied separately. proposed measuring instrument easily realized with off-theshelf gate circuits proved good estimation real transmission systems. block diagram measurement unit given figure complete circuit diagram figure
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Received data EXOR linkage Transmitted data Time delay adjustable linkage error output
Clock
Time delay adjustable
Clock output (optional)
Figure Block diagram measuring instrument
Delay downward slope data Delay upward slope data 74LS123
74LS86
74LS86 invert data
Received data Transmitted data
74LS08
error (Clock out) Clock
74LS123 Delay upward slope clock
Delay downward slope clock
Ground
Figure Circuit diagram measuring instrument
dimensioning measurement unit carried data rates kBaud, signals based level. adjustable time delay realized with double mono-flops type 74LS123 conjunction with quad EXOR linkage 74LS86. With component values given circuit diagram, maximum delay time approximately delay
times upward- downward slope data must equal, that length will changed. sampling instant well duration decision time individual adjustment delay times upward- downward slope clock.
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lowpass filters inputs gate 74LS08 eliminate pulse spikes that generated EXOR linkages their input signals switched exactly same time. time constants elements were that influence data nearly neglectable data rates about kBaud. Figure shows measurement error rates AMand transmission with various deviations. this example, pseudo random sequence 25-1 transmission rate kBaud used. measurement taken U4311B with AC-coupled data filters. time decision, whether right wrong decoded, middle bits. length short compared length bit. measured level corresponds carrier peak level output used signal generator, according "high-level" square wave signal. previous diagram shows that system's sensitivity, thereby operation distance enlarged constant transmitter output power receiver sensitivity higher deviation. System optimizing done transmitter part, too.
0.01 0.001 0.0001 input level (dBmV)
system superior system used deviation more than kHz. deviation kHz, margin about this comparison, low-pass filter with voltage gain used AC-coupled filter, DC-coupled filter dimensioned according figure gain value AC-coupled data filter DC-coupled filter, latter dimensioned according figure seen, that margin between wake-up threshold limiting sensitivity approximately actual dimensioning.
input level (dBmV)
Wake-up threshold
Modulation depth deviation (kHz)
Figure sensitivity 10-3, AC-coupled data filter
deviation 22.5 modulation depth 100% deviation input level (dBmV)
Wake-up threshold
Figure error rates kbit/s length 25-1, AC-coupled data filters
following measurements give comparison sensitivity U4311B data transmission with error rate (BER) below 10-3 mode. Within next chapters, will examine AMand system more closely. Figure shows dependence with AC-coupled data filters, figure measurement result quasi DCcoupled filters. system using modulation depth 100% achieves claimed lower input levels than system using 22.5-kHz deviation. seen, that modulation depths above 60%, sensitivity nearly constant. without decrease performance, modulation depths below 100% used, which method reduce transient times operation.
Modulation depth deviation (kHz)
Figure sensitivity 10-3, quasi DC-coupled data filter
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Operation
mentioned before, system realized with less costs compared link. system, this applies mainly transmitter, while receiver side additional expense small. amplifier provides wide dynamic range gain controlled, settling times have considered when choosing code data transmission. However, rise time simple one-stage-transmitter limits maximum data transmission rate. demodulator logarithmic type that rectified voltage compressed avoid overshooting following operational amplifier. used also systems Received Signal Strength Indicator (RSSI).
seen, operation range demodulator covers more than decades. This corresponds capability simple tuners, higher dynamic ranges require gain-controlled tuner. However, with regard given transmitter output power, such additional expense does seem necessary. input levels above dBµV, output current decreases. utilizing modulation with small modulation depth, such high input levels should applied avoid inverting demodulated data signal. With modulation depth more than 60%, this problem does appear. Compression effects disturb digital system, because such high signal levels signal-to-noise ratio very high shown later. dependence supply voltage very low, shown figure seen that supply voltage range from variation wake threshold less than output stage supplied internal reference voltage obtainable output voltage limited this value. this reason, maximum reasonable value load resistance considered that this resistor determines output impedance which must obeyed dimensioning following data filter. utilizing quasi DC-coupled filter, additionally taken into account.
output current (mA)
Demodulator Characteristic
logarithmic demodulator output current source that provide output current approximately measurement setup same used examination parameters according figure measurements concerning demodulator characteristic, data filter should connected demodulator output avoid unwanted feedback. characteristic demodulator versus input level different temperatures shown figure input levels, good temperature dependence evident. Thereby, wake threshold, which determines input sensitivity wake mode finally operation range transmission system nearly independent temperature. This threshold typically dBµV loss resistors this corresponds approximately 45.5 dBµV input test board. spread output signal high input levels compensated sliding comparator therefore without influence transmission quality.
Supply voltage Supply voltage Supply voltage
input level (dBmV)
output current (mA)
Figure AM-demodulator characteristic input level various supply voltages
+85°C +25°C -40°C
input level (dBmV)
Figure demodulator characteristic input level different temperatures
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Signal-to-Noise Ratio
signal-to-noise ratio standard signal quality. define Signal Noise Noise (S+N/N) ratio digital system with 100% modulation depth, first necessary distinguish between different kinds noise:
output voltage VS+N (dB)
level:
Measured with input signal, therefore noise constant.
(low level)
(high level)
High level:
Measured with unmodulated carrier. While raising level carrier from dBmV approximately dBmV, noise increases because level dependent directivity logarithmic detector. With higher values input level, amplification amplifier therefore also noise decreases.
input level (dBmV)
Figure Signal-to-noise ratio without data filter
(S+N)/N ratio difference between (S+N)and curves. This ratio increases from limiting sensitivity dBµV more than referred Nhigh, respectively referred Nlow, input level dBµV. fact, effective (S+N)/N ratio lies between those values depends probability high bits. maximum signal-to-noise ratio limited noise, respectively dynamic range receiver. (S+N)/N measurings, only thermal noise, which considered white Gaussian noise, present. Therefore, sensitiveness systems pulse noise, example ignition noise, does become evident. rule thumb, (S+N)/N ratio sufficient secure data transmission, course this value depends amount transmitted data. results measurements (see figures agree with this rule. (S+N)-curve measured with modulated carrier, modulated either with sine wave rectangular signal. Figure shows signal-to-noise ratio output modulation depth 100%. voltage level (RMS) signal measured while data filter decoupled. configuration measurement corresponds figure with exception meter, which connected output. bandwidth meter limited 22-kHz lowpass filter. signal-to-noise ratio improved insertion data filter (here: AC-coupled type, voltage gain -5), shown figure Here, voltage level output (Pin AC-coupled data filter measured. With exception data filter dimensioned according figure measurement setup seen figure
measurement result with quasi DC-coupled filter according circuit diagram figure seen figure filter voltage gain exceed comparator's limiting sensitivity even input levels. raising voltage gain, receiver's sensitivity improved, though ratio deteriorates. This because absolute value low-level noise increased enlarged filter gain.
filter output voltage VS+N (dB)
(low level) (high level)
input level (dBmV)
Figure Signal-to-noise ratio with 2-kHz Bessel lowpass filter, AC-coupled,
filter output voltage VS+N (dB)
(low level) (high level)
input level (dBmV)
Figure Signal-to-noise ratio with 4-kHz lowpass filter, quasi DC-coupled,
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Operation
U4311B/ U4313B enable realization operation with expenditure. Only discriminator filter resistors, R15, have added compared operation. performance link correlated system bandwidth, measurement versus frequency deviation figures have already shown. optimum system bandwidth depends deviation, manufacturing tolerance frequency determining elements transmitter receiver's local oscillator. Their frequency drift with temperature considered well. most current solution achieve stable transmission frequency resonator. Usually, such resonators available with manufacturing tolerance kHz, with additional temperature drift range kHz. same tolerances appear both transmitter receiver, total amount tolerances kHz. bandwidth receiver's processing matched system. former consists mainly bandwidths discriminator filter. Because tolerances, discriminator filter advantageously should tunable that manufacturing tolerance receiver's resonator equalized. taken into account that receiver transmitter normally work temperatures different from each other, proposed discriminator bandwidth kHz, according figure with sufficient actual conditions, i.e., frequency deviation between kHz. Using SAW-based transmitters, higher frequency deviations achieved easily. resonators with 75-kHz tolerance market, devices with under development. TEMIC recommends these components achieve best possible system performance. other concepts used stabilization operation frequency, instance X-tal controlled systems, adjustment discriminator's center frequency might necessary. this case, also single-ended ceramical discriminator filters used, connected directly from ground. another benefit, given system bandwidth approximately better exploited higher frequency deviation more.
Discriminator Characteristic Bandwidth
preceding explanations showed that necessary bandwidth part determined tolerance SAWs rather than deviation transmitter. With increasing bandwidth discriminator, amplitude output signal decreases therefore signal-to-noise ratio deteriorates which reduces obtainable operation distance. demodulator stage suited discriminator filter single-ended type well known from integrated one-chip radio circuits. discriminator works 800-W load therefore matched directly ceramical resonator. discriminator filter also composed discrete components formed L/C-tank circuit, that adjustment center frequency possible. discriminator filter should temperaturecompensated ensure constant center frequency over operating temperature range. discriminator filter notch type. demodulator bandwidth depends hand from difference between serial parallel resonance discriminator filter, adjustable series capacitor C10.
Output voltage 10.3
10.4
10.5
10.6 10.7 10.8 Frequency (MHz)
10.9
11.1
Figure Characteristic discriminator
other hand, steepness S-curve adjusted external resistors R14, R15. higher values resistors, bandwidth decreases. been mentioned formerly that these resistors component output resistance which must well-defined correct operation following data filter. influence variation resonances, here achieved variation C10, illustrated figure meet best transmission characteristic system, cut-off frequency discriminator should correspond bandwidth receiver's overall frequency response. measurement setup seen figure data filter must decoupled from demodulator output. voltage output measured, level applied test board dBµV.
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Data audio frequency generator output
Power supply
input Level shifter (optional) output
Modulation input Signal generator output
Power supply Comparator output Data Data filter output input Wake-up switch
Circuit entirely turned
Voltmeter
test board
output (Pin output (Pin Field strength output Wake-up output
Wake-up function
Figure Setup measurement characteristic
Signal-to-Noise Ratio
Figures present signal-to-noise ratios versus input level test board with operation various types data filters frequency deviations. measuring carried analogy that receiver, measurement setup corresponds figure Figure shows signal-to-noise ratio frequency deviation 22.5 without data filter, limiting sensitivity dBµV therefore worse compared that system. However, (S+N)/N ratio increases more rapidly with input level threshold effect system. Here, benefit system becomes obvious: level signal therefore also noise independent transmitted information. Therefore, (S+N)/N ratio higher input levels better than that receiver. signal-to-noise ratio input levels improved data filter clearly illustrated figure this measurement, AC-coupled data filter according figure used. corresponding graph quasi DC-coupled data filter dimensioned according figure shown figure Finally, signal-to-noise ratio frequency deviation given figure using same quasi DC-coupled data filter measurement before.
TELEFUNKEN Semiconductors 08.97
output voltage VS+N (dB)
filter output voltage VS+N (dB) input level (dBmV)
input level (dBmV)
Figure Signal-to-noise ratio without data filter, deviation 22.5
Figure Signal-to-noise ratio with 2-kHz lowpass filter, quasi DC-coupled, deviation 22.5
filter output voltage VS+N (dB)
input level (dBmV)
filter output voltage VS+N (dB)
input level (dBmV)
Figure Signal-to-noise ratio with 2-kHz Bessel lowpass filter, AC-coupled, deviation 22.5
Figure Signal-to-noise ratio with 2-kHz lowpass filter, quasi DC-coupled, deviation
TELEFUNKEN Semiconductors 08.97
Circuit Diagrams
printed circuit board identical types receiver suited well operation. Both types data filters, matter quasi DC-coupled realized. adaptation desired modulation type carried component assembling. wake comparator output equipped with open collector. test circuits, these outputs referred stabilized voltage VRef means resistors respectively R13. also offers option refering outputs supply voltage This possibility favorable espe-
cially with regard connection microcontroller with supply voltage data input microcontroller provides internal pull resistor, left out. order couple input ceramical filter 10.7 also used instead C11. layout offers both possibilities. suited connector input. discriminator tank replaced singleended ceramical discriminator. this case, replaced bridge. recommend ceramical discriminator MURATA 10.7 which offers bandwidth kHz.
Figure Universal layout test circuits, scale 2:1, view: component side
TELEFUNKEN Semiconductors 08.97
Test Board Operation
test circuit with 2-kHz Bessel lowpass data filter with AC-coupling, (same circuit U4311B)
input
Wake-up output
U4313B
Wake
Data filter output Comparator output
Figure Circuit diagram
Part list
Figure Components placement
TELEFUNKEN Semiconductors 08.97
test circuit with 4-kHz lowpass data filter with quasi DC-coupling, (same circuit U4311B)
input
Wake-up output
U4313B
Wake
Data filter output Comparator output
Figure Circuit diagram
Part list
Figure Components placement
TELEFUNKEN Semiconductors 08.97
Test Board Operation
test circuit with 2-kHz Bessel lowpass data filter with AC-coupling, (same circuit U4311B)
Filter (optional)
input
Wake-up output
U4313B
RSSI
Wake
Data filter output Comparator output
Figure Circuit diagram
Part list Filter TOKO A119ACS-19000Z
Figure Components placement
TELEFUNKEN Semiconductors 08.97
test circuit with 2-kHz lowpass data filter with quasi DC-coupling, (same circuit U4311B)
Filter (optional) input
Wake-up output
Wake
U4313B
RSSI
Data filter output Comparator output
Figure Circuit diagram
Part list
Filter TOKO A119ACS-19000Z
Figure Components placement
TELEFUNKEN Semiconductors 08.97
Complete Remote Control System
following circuits within this section proposals complete link realized. design PCBs range presumes care experience, also appears component. most critical parameters size quality discrete components. producer such subassemblies, possibilities potential mass production have considered.
modulation input Loop antenna 433.92 optional modulation input
Circuit Proposal Transmitter Operation
Within this chapter, circuit proposal given which just give idea realize transmitter. There nevertheless other possibilities. practice, transmitter module contains only transmitter, also either data control interface even encoding. However, will only discuss transmitter's part. simple design, consists only single stage, SAW-based oscillator whose inductance tank circuit realized loop acts also antenna. When designing transmitter, quality factor, loop antenna important. doubling yields four times larger total transmitted power. Another benefit high less obvious, least important. higher quality factor, greater ratio effective current fundamental wave compared current harmonics because resonance step-up appears only resonance frequency antenna circuit. Therefore, suppression radiated harmonics essentially determined quality factor aerial. will have closer look theoretical background within chapter example simple single-stage transmitter operation 433.92 given figure amplitude-modulated switching base voltage transistor (Amplitude Shift Keying, ASK), well frequency-modulated help varicap tank circuit. varicaps used realize almost powerless frequency modulation. operation desired, left out. this case, replaced capacitor transmitter works with supply voltage between (two lithium cells). applying supply voltage, data signals with level used modulation.
Figure transmitter circuit diagram
Part list 433.92 MHz, Siemens Matsushita 2527 S852T BB804
Circuit Proposal Superheterodyne Receiver
TEMIC's proposal low-current receiver includes previously commented standby concept conjunction with special circuit arrangement consisting stacking circuit stages current reducing. This stacking appears, hand inside tuner, other hand cascading entire tuner with remaining baseband parts which covered receiver principle configuration receiver seen figure signal path considered, input stages cascaded achieve higher sensitivity better rejection local oscillator radiation compared single-stage preamplifier. mixer self-oscillating type master1-excited, depending requirements large-signal behavior. both types, local oscillator stabilized resonator. Varying current consumption between front circuitry buffered Zener diode. power consumption section lower than that part dependent receiver mode Zener diode takes over differential current between active standby mode. clamps front supply voltage approximately
TELEFUNKEN Semiconductors 08.97
achieve sufficient stabilization, low-current Zener diode helpful. total supply current unit limited circuit series resistor necessary.
Figure shows circuit proposal low-current receiver working 433.92 according concept described before. receiver designed 18-V supply voltage total quiescent current consumption approximately Coming from antenna input with characteristic impedance received signal passes doubletuned miniature helical filter. This pre-selector provides good far-off selectivity, improves image rejection makes subsequent prestage insensitive deviations antenna impedance. preamplifiers common base circuit DC-cascaded. grounded base amplifiers distinguished high reverse isolation guarantee good suppression local oscillator signal antenna input. Maximum gain input stages achieved tuning L101, L102, C109. level well spurious response harmonics less than port receiver module, encased plate cabinet shielding. tuner, special low-noise, low-current, low-voltage bipolar transistors applied. transition frequency used S852T given collector current which provides gain about stage 433.92 MHz. Alternatively S822T used, providing slightly improved transition frequency compared S852T. Using common base circuit, input impedance these transistors approximately collector current following self-oscillating mixer, signal converted intermediate frequency 10.7 MHz. large-signal characteristic receiver improved using master-excited mixer proposed figure whereby complexity circuitry power consumption slightly increased. means resonator frequency determining element, local oscillator oscillates high frequency
Power supply
band therefore frequency multiplication necessary. This results tuner free spurious resonances minimal expense. oscillator frequency adjusted exactly tuning L104. Zener diode D101 keeps operating points transistor stages tuner constant although total current consumption depends mode receiver. protection against wrong polarity power supply, suppressor diode D102 used. Compared diode series with receiver, causes voltage drop used also transient suppression. tuner works without Automatic Gain Control (AGC) avoid settling time problems especially systems. Therefore, dynamic range subsequent stages must kept view. part dimensioned according figure operation with ACcoupled data filter. Special care taken when designing layout printed circuit board. This necessary avoid parasitic oscillations coupling ground lines. preceding subsequent circuits correspond first samples built examinations lab. More detailed information about complete links given separate paper. Another receiver circuit proposal with part designed operation given figure tuner, master-excited mixer used, realized kind cascode circuit with local oscillator. mixer gain enlarged insertion C116. L107 C112 work absorption circuit C111 suppresses backward mixing collector base diode T103. given polling concept, part designed circuit with minimal expense. data filter simple lowpass filter first order with voltage gain -25, high-frequency cut-off kHz. diode D102 inserted avoid damage caused wrong polarity supply voltage. voltage drop this diode, supply voltage range receiver shifted higher values (approximately plus
input
U4313B
Data output
Signal path Power supply
Figure receiver unit schematic diagram
TELEFUNKEN Semiconductors 08.97
D102
C101 C113
L106 D101 10.7 R103 L105 C114 R104 L104 C109 C111 T103 C112 C110 R107
423.22
L101
C102 T101 C104 R101 C105
C103
R108 C115
Wake-up output
U4313B
RSSI
L102 L103 C106 T102 C108
R105
C107
R109
Data output
R102
R106
Figure Circuit diagram
Part list
TOKO A119ACS-19000Z
T101 S852T T102 S852T T103 S852T D101 (Rohm) D102 BZT03/D18 (TEMIC TFK)
R101 R102 R103 R104 R105 R106 R107 R108 R109 L101,102,104 coils, winding turns, wire L103 helical filter COMPONEX 40545 L105 transformer 12:3, TOKO A119ACS-18999N (without internal capacitor) L106 resonator 423.22 2531 (Siemens Matsushita Components)
C101 C102 C103 C104 C110 C105 C106 C107 C108 C109 C111 C112 C113 C114 C115
TELEFUNKEN Semiconductors 08.97
C101
C110 R103
L106 D101 D102
R106 C103 C111
L105
L101
C102
10.7
T101 C104 R101 C106 L102 L103 T102 C109 R102 R105 C108 C114 R108 R109 T104 C115 R104 L104 C105 C107 R107 C113 C116 T103 L107 C112
U4311B U4311B
Modecontrol input
423.22
Data output
C116 optional
Figure Circuit diagram receiver unit operation using master-excited mixer, polling method
Part list T101 T102 T103 T104
S852T S852T S852T S852T
C101 C102 C103 C104
D101 (Rohm)
D102 1N4148 R101 R102 R103 R104 R105 R106 R107 R108 R109 L101,102,104 coils, winding turns, wire L103 helical filter COMPONEX 40545 L105 transformer 12:3, TOKO A119ACS-18999N (without internal capacitor) L106 L107 resonator 423.22 2531 (Siemens Matsushita)
C105 C106 C107 C108 C109 C110 C111 C112 C113 C114 C115 C116
TELEFUNKEN Semiconductors 08.97
Complete Link
Normally, transmitter custom-designed, accordance requirements size, coding system, output power specifications, etc. receiver designed universal module. unit custom-specified operation desired data telegram component placement selection. Last least forecast possible further developments given. Another application report available, containing more information about complete receiver [9]. This report based explanations measurement techniques developed within report hand. Focus given tuner, discussing circuit proposals measurement results. PLL-based transmitter U2740B developed with better frequency tolerance improved modulation capability. limited modulation capability actual SAW-based transmitter design, frequency deviation limited less than kHz. Unfortunately, tolerance SAWs demand band-width more than kHz. this reason, increase deviation about will result improvement system-sensitivity approximately Certainly semi-duplex full-duplex radio links will needed special applications these will included future activities.
Summary Future Considerations
This report described function integrated circuits U431xB explained fundamental system aspects. Some applications receiver were discussed giving comprehensive design hints application circuits including layout. applied measurement techniques, which have been illustrated, make possible characterize optimize complete system. resulting circuit proposals presented this report were realized first samples laboratory worked well.
TELEFUNKEN Semiconductors 08.97
Appendix
(Study radio wave radiation propagation operating frequency harmonics)
this chapter, theoretical relation radiation propagation radio waves given great details. This serve point most important parameters link some physical criteria choice optimal operating frequency range. using small-tuned loop antenna, will shown which parameters optimized achieve maximum effective radiated power operating frequency, while keeping emission harmonics low.
Next, total radiated power, such small loop turns area, respectively diameter, which tuned with parallel capacitor, deduced analogically that electrical Hertzian dipole [4]. Assuming spherical coordinate system, electric magnetic intensities
Transmitter
Receiver
Figure link
benefits range become obvious study radio wave propagation versus frequency. simplification, free-space propagation assumed only field region considered. Referring transmission frequency, respectively wavelength, received power, distance, from transmitter, with output power, antenna gain, referred isotropic radiator, respectively, receiver side according reference
related free-field characteristic impedance
surface integral power density, yields total radiated power,
logarithmic attenuation ratio, free-space propagation defined
32.5
Substitution electric intensity solving integral yields
Taking widespread demand small size into account, small loop antenna seems good choice. pattern such antenna equal that Hertzian dipole with gain 1.5. Supposing transmitter, well receiver antennas, that kind 1.5), following achieved from equation
29.0
TELEFUNKEN Semiconductors 08.97
with
Quality factor loop antenna
max| Hence
(10)
1000 1500 2000 2500 Frequency
(11)
Figure Assumed quality factor loop antenna versus frequency
quality factor, resonant circuit determines resonance step-up loop current. With impressed output current, from transmitter antenna, effective loop current equal (12)
Furthermore, area, circular loop with diameter,
(13)
Herewith
Exemplary, total transmitted received power calculated MHz, 433.92 2400 because these frequently used bands. corresponding values roughly estimated 100, Assuming transmitted power, above mentioned frequencies -56, dBm, whereas received power, distance will -83, respectively. This applies free-space propagation shows that higher frequencies favorable when using such small antenna. Figure shows dependence received power versus loop diameter, frequency, fixed distance assumed quality factor, loop antenna versus frequency drawn figure
(14)
Received power/
Substituting from (14) (1), following derived
(15)
with assumption (two small single-turn loop aerials) finally
-100
(16)
Figure Received power, distance versus frequency, antenna loop diameter,
seen from this formula, received power directly proportional whereas inversely proportional This equation only valid diameter, loop small compared wavelength, Furthermore, independent Particularly losses skin effect increase with frequency reduce Therefore, owing circumstances practical optimum does exist. TELEFUNKEN Semiconductors 08.97
practical operation, some additional factors influence propagation characteristic. Diffraction reflection radio waves edges conductive surfaces well their capability penetrate dielectric materials frequency dependent. shielded metallic structures size gaps slots structure small compared wavelength. This fosters higher frequencies well. other hand, bears mind that propagation losses absorption
Loop diameter
2000 1600 1200
Frequency
regard radiation characteristic small loop aerial. According [4], such loop's inductance
(17)
constant determined geometry loop. Taking circular loop 1.07, quadratic loop 1.47 finally 1.81 equilateral triangular loop according [4]. consider circular loop with wire gauge therefore circumference, (18)
Figure loop antenna 433.92 versus
effective loop current, operating frequency
Equation (17) only valid This boundary condition implies that constant almost influence inductance therefore this regard geometry aerial quite uncritical. mentioned before, effective radiated power essentially determined loop current resonance step this current such parallel resonance circuit function quality factor,
with resonance step-up factor
respectively
shown equation (12) effective loop current fundamental frequency therefore effective loop current n-th harmonic from following equation (24):
Figure Equivalent circuit tuned loop antenna
capacitance, equivalent shunt resistance,
(19) with resonance step factor
(20)
Figure shows characteristic circular loop with wire gauge versus loop diameter,
respectively
Loop diameter
reflections dielectric layers (e.g. window panes) increasing rapidly frequencies above GHz, range appears best frequency choice purposes. Moreover, absorption radio waves band molecules beneficial because this pays regard human protection.
kOhm;
(21)
(22)
(23)
(24)
(25)
(26)
TELEFUNKEN Semiconductors 08.97
relation between impressed effective loop current fundamental first harmonic frequencies plotted figure operation frequency, 433.92 MHz, quality factor, assumed.
Quality factor
10000 1000 0.01 0.001 0.0001 0.01
Figure Radiated power 433.92 harmonics versus
Figure Effective loop current 433.92 harmonics versus impressed loop current
Finally, effective radiated power loop antenna fundamental wave harmonics considered. With regard fundamental wave, following derived
Figure Radiated power 433.92 harmonics versus
(27)
-100 -120 0.00001 0.0001 0.001 0.01
referring n-th harmonic following analogously deduced
(28)
Figure Radiated power 433.92 harmonics versus
should noted that equations only valid D<<l. Among others, radiation pattern higher harmonics quasi isotropic. Substituting equations (17), (19), (20), (21), (24) into equations (27), (28), assuming
seen that 433.92 MHz, radiated power fundamental wave approximately dBm, first harmonic second harmonic dBm. Therefore, suppression first harmonic whereas second harmonic. conclude once more, emphasized that previous considerations were based several approximations simplifications. Nevertheless, results accordance with practical investigations. least they well suited appraise individual practical results deduce possible objects optimization.
(29)
derive subsequently shown three diagrams figures TELEFUNKEN Semiconductors 08.97
Remote Control System: Receiver Front Complete Receiver Design Hints
Introduction
This report description develop costsaving superhet receiver radio-frequency-based remote control systems range. should seen completion previous main chapter. complete receiver consists front end, part microcontroller. based receiver TEMIC's U431xB family. Circuit configurations either standby current supply voltage possible. main goal front-end development design assembly that meets practical require-ments with reduced number components alignments, while achieving excellent sensitivity wide dynamic range. production line, only low-cost measurement equipment necessary testing tuning. First, principle circuit arrangement illustrated with different configurations make either low-voltage low-current receiver. Next, circuit proposal front shown, using TEMIC's high performance transistors S852T. Finally, complete remote control receiver introduced, optionally including signal decoder that designed with low-current microcontroller (µC) M44C260 family. suggested circuits have been tested practice demo boards components were developed. These boards ready series production, only demonstration system features. They suitable different operation frequencies, either amplitude frequency modulation wide range supply voltages. Four different versions have been completely specified part lists them included appendix. measurement results this paper were taken these demo boards. range, printed circuit board must regarded component. layout co-determines performance. development always done under different guidelines, circuits introduced here only used basis customer's developments. will necessary adapt circuits requirements series production.
Circuit Arrangement Complete Receiver
receiver based modular concept, such that there different options interconnection subcircuits front end, part signal decoder (e.g., µC). choice these circuit arrangements determined requirements supply voltage, supply current sensitivity. Circuit configurations their features using different integrated circuits given table Figure represents low-current version with standby current active mode current excluding current consumption microcontroller. Zener diode used limit front-end supply voltage with increasing receiver supply voltage. optional resistor might necessary receiver switched between active passive mode front designed exactly current consumption. passive mode, supply current part also without additional resistor, current would left Zener diode. exception U4314B, with total current consumption current constant, diode resistor left out. supply voltage range this setup low-voltage applications, setup shown figure useful. order limit current consumption, supply voltage should stabilized otherwise restricted values between 4.7-V Zener diode used stabilization series with resistor, supply voltage range achieved.
Front
part
Microcontroller
Figure stacking front part
Front
part
Microcontroller
Figure Front part parallel
TELEFUNKEN Semiconductors 08.97
Table Characteristics remote control receivers with various circuit arrangements
Type
U4311B U4313B Wake-up Polling Concept According Figure According Figure
U4314B Continuously Active, without Data Filter According Figure According Figure
Minimum supply voltage Supply current standby (incl. regulation, excl. DPU) Supply current permanent active (incl. regulation, excl. DPU) Sensitivity 80%, resp. deviation 22.5 kHz), Wake-up threshold Wake Permanent controller activated Modulation system Relative system transmission rate with single stage transmitter
High
High
Front Remote Control System
front end, PCBs have been designed. circuit diagram shown figure identical both versions. layout shown figure figure suited combination with part according figure figure part presented [1]. second given figure figure already includes part. tuner suited either parallel circuit with part stacking with shown figure figure latter configuration, ground planes front part same voltage level, C100 must used antenna connector avoid short circuit shielding antenna cable grounded. value critical, proposed. front designed supply voltage current consumption approximately supply voltage increased that Zener diode D101 this voltage used stabilization supply voltage stabilized other means. With increasing supply voltage, supply current also increases. Therefore, least emitter resistors (R104 R109) have changed front work with different supply voltage supply current. Circuit variations 5-V- supply voltages have been tested achieved same sensitivity. characterize front end, combined with part according figure 40]. Test results measurement conditions discussed this chapter.
TELEFUNKEN Semiconductors 08.97
Circuit Alignment Description
front consists prestage designed with T101 T102 cascode circuit local oscillator with T103 mixer with T104. complete characterization 433.92-MHz 303.85-MHz operation frequency carried out. layout component placement shown figures cascode circuit chosen decouple local oscillator antenna input order suppress radiation local oscillator. Measurements several modules based system showed that level local oscillator antenna input approximately dBm.
supply current effects low-noise figure preamplifier. input filter (C101 C103, L101 L102) provides far-off selectivity. 3-dB bandwidth input filter approximately MHz, tuning coils should necessary. high transit frequency transistors, necessary connect C104 ground plane opposite side order avoid oscillations (see arrow figure same purpose, R110 inserted, shown figure prepared these modifications. position where printed conductor insertion R110 marked with asterisk figure front combined with part (figure already includes modifications. amplified signal base mixer transistor, T104. wide transmission range required, value C107 increased while decreasing C106. This will improve strong signal behavior, while decreasing receiver's sensitivity. developed front requires only alignments. prestage gain maximized tuning L103. maximum output voltage receiver indicates correct adjustment. alignment prestage, local oscillator must, course, locked operation frequency. local oscillator Colpitts type common base circuit. Normally, coil (L104) must tuned that oscillator l
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