3902 AN3902 Demonstration Board AS3902 Band Transmitter
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Band Transmitter
3902
AN3902
Demonstration Board AS3902 Band Transmitter
Application Note Rev. March 2001
Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
General Description
AS3902 demonstration board designed demonstrate functionality transmitter. main functional blocks are: AS3902 band transmitter Printed circuit board loop antenna. ATMEL AT90S1200 micro controller interface.Applications
Features
Supports European band. frequency pulling (antenna) load variation synthesizer. Designed conform 220-1 requirements. Data rate range from kbit/s. Supports clock reset signals external Supports total shut down mode without running XTAL oscillator. Only external components required. Operation possible XTAL pulling. Wide supply range between current, typical transm. ,,H", transm. ,,L". Wide operating temperature range from Miniature surface mount MSOP package.
Scope
This application note describes operation AS3902 transmitter demonstration board. This circuit board fully operational transmitter including small printed loop antenna micro-controller (µC) data generation. Several test modes, data patterns data rates selected switch.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Demonstration board (Original size mm).AS3902 Please refer AS3902 Data Sheet details operation (Reference list page 14).
Loop Antenna
AS3902 demonstration board includes small printed circuit magnetic loop antenna. This type antenna especially cost effective convenient small hand-held transmitters. However, design such small loop antenna requires some care. small loop antenna modeled series connection inductor resistors, representing electrical length than quarter wavelength) loop, ohmic loss resistor radiation resistor. Unfortunately this type antenna very efficient radiation resistor generally much smaller than loss resistor.
Rloss
Rradiation
Figure Equivalent circuit small loop antenna. operation, antenna typically tuned parallel resonance desired frequency means parallel capacitor. this case input resistance loop antenna will very high unusually operated series resonance with series compensation capacitor, impedance will very ).In other words: small loop antenna high device efficient device. AS3902 output stage differential open collector output, which delivers available peak output power typical into load. order achieve this desired impedance level impedance transformation necessary. should noted that, high efficient transmitters usual, this impedance transformation achieve conjugate match AS3902 output rather generate real load impedance optimized ARMS collector current differential output swing combination AS3902. loop inherently inductive used transformer element itself. connecting output AS3902 intermediate point loop shown Figure desired impedance transformation achieved without additional losses additional costs. proper selection tapping point tuning capacitor wide range impedance levels achieved.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
tapping Ctune
Figure Example loop antenna with antenna matching tuning. Furthermore this antenna structure allows proper biasing open collector output. objects within loop will influence performance generally degrade efficiency. maximum effective radiated power empty loop should used. this possible other design restrictions additional objects should small possible especially conductive loops should avoided. Further details small loop antennas found Reference list, page
Microcontroller Interface Power Management
AS3902 designed directly interface microcontroller (µC). interface consists three pins: ,,Transmit data input" (TXD). ,,Active ,,L" reset output transmitter power down input" (NRES/PD).
,,µC clock output active ,,L" wake-up input" (CLK/NWUP).
These lines support with required reset clock signals control AS3902 internal power on/off circuit which wakes shuts down whole transmitter consisting AS3902 actual implementation interface depends specifications. cases considered here: 2.2.1 with Static Power Down Reset State (Type Figure shows typical interfacing AS3902 type Figure presents related timing power down transmitter. type remains power standby mode long NRESET ,,L" clock cycles applied.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
AS3902
SERIAL DATA TRANSMIT NRESET CLOCK
NRES/PD CLK/NWUP Transmit switch
Figure Interfacing AS3902 typical
open
closed
CLK/NWUP NRES/PD standby startup clocks clocks transmit clocks standby
Figure interface timing transmission cycle.
Note 1:The dashed lines indicate weak high state when CLK/NWUP NRES/PD output AS3902 disabled high-resistive state) pulled ,,H" ,,L" internal pull-up device resistor. These weak states overridden AS3902 respective outputs enabled.
Whenever line pulled external resistor, however, this should override internal pullup devices AS3902. Standby: During standby XTAL oscillator turned AS3902 holds reset state:The AS3902 NRES/PD active ,,L", holding reset state. standby mode AS3902 internal NRES/PD pull-up disabled drain current from supply. AS3902 CLK/NWUP output disabled, high resistive ,,Z" state) internally pulled ,,H". (Re) starting transmitter: Closing push button (giving falling edge CLK/NWUP CLOCK line) starts AS3902. turns XTAL oscillator after oscillator start phase turns CLK/NWUP active (CMOS level) mode provides clock After delay clock cycles NRES/PD AS3902 ,,H" clock cycles. This rising edge NRES/PD starts should program output
Rev. March 2001 page
Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
,,H" disable (set high-resistive ,,Z" state) within this clock periods AS3902 than will disable (set high-resistive ,,Z" state) NRES/PD output again with internal pull-up active. Than turn synthesizer driving amplifier rhythm data (Serial data out) line transmit data. Bringing transmitter standby: After completing transmission, indicate ,,end transmission" setting (inv. transmit) ,,L" pull NRES/PD NRESET line ,,L". Sensing this, clock cycles later AS3902 will switch back standby mode, disabling CLK/NWUP output turning XTAL oscillator. Repetitive transmission: button still pressed when indicates ,,end transmission" setting ,,L" pulling NRES/PD NRESET line ,,L", clock periods later sequence above repeated starting from clock delay period. sophisticated tri-state active inactive pull-up configuration NRES/PD AS3902 does drain current during standby periods.
2.2.2 with Quasi Active Power Consumption Reset State (Type Some have level triggered rather than edge triggered internal reset generation, some have Pull resistors NRESET input allow save Power Reset (POR) generation. either case there will undesired power consumption standby mode. this situation following interfacing AS3902 will overcome problem.
AS3902
NRES/PD CLK/NWUP
SERIAL DATA TRANSMIT NRES CLOCK
Transmit switch
Figure Interfacing AS3902 Type
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
open closed
NRES NRES
standby startup XTAL reset clocks standby
NRES after Clock Cycles
Figure Interface timing transmission cycle with Type (see Note Page Standby: During standby XTAL oscillator turned AS3902 holds reset state: AS3902 NRES/PD active ,,L". AS3902 CLK/NWUP output disabled, high resistive ,,Z" state) internally pulled ,,H". (Re) starting transmitter: Closing push button (giving falling edge CLK/NWUP CLOCK line) starts AS3902. turns XTAL oscillator after oscillator start phase turns CLK/NWUP active (CMOS level) mode provides clock long push button pressed reset. Once push button released XTAL oscillator already started initialization phase begins. AS3902 kept awake internal pull NRES. Therefore needs output either logic high resistive ,,Z" state signal pin. Then turn synthesizer driving amplifier rhythm data (Serial data out) line transmit data. Bringing transmitter standby: After completing transmission, indicate ,,end transmission" setting (inv. transmit) ,,L" pull NRES/PD line ,,L". Sensing this, clock cycles later AS3902 will switch back standby mode, disabling CLK/NWUP output turning XTAL oscillator. needs programmed enter power down sleep mode during this clock cycles.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Application Schematic
Note Inductor omitted feed loop antenna connected ground. Such ground e.g. symmetric point loop used demonstration board.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Figure Application board schematic.
Rev. March 2001
EMB4466.tmp-1 15:42:19 2000
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Board Layout
Figure Component arrangement side.
Figure Component arrangement bottom side.
Figure layer (component side).
Figure Bottom layer.
List Components Number
Transmitter Processor R1,R2 U4,U6 AS3902 XTAL Capacitor Capacitor Capacitor Inductor AT90S1200 Resistor Capacitor Capacitor Capacitor Diode switch Push button Battery 13.56 MHz, transmitter Frequency reference Supply decoupling XTAL pulling Antenna tuning isolation (optional) wired function Supply decoupling Supply decoupling Clock filter wired function mode select Start stop operation Power supply
Component
Value
Purpose
kOhm BAS21
Table List components
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Program
generates test signals several test modes data rates. These modes selected switch. Please refer Table for.mode selection:
Mode
Continuous series .0101., interrupted pushing power down switch PRN9 single shot: System enters sleep mode after cycle. PRN9 continuous series, interrupted pushing power down switch Continuous wave transmission, interrupted pushing power down switch
Table Available test modes. PRN9 pseudo random noise signal, generated with shift register method. length shift register bit.In case PRN9 single sequence trigger signal output beginning PRN9 series ease analysis transmitted signal.A wider range data rates selected with switches Please refer Table details available data rates. Different data rates achieved adding appropriate number cycles program flow.
app. Data Rate kBit/s]
24.5 0.57
Table Data rates.
Note 3:Due programming restrictions given data rates only approximate numbers differ slightly from 01010 series PRN9 series.
used inputs programmed have internal pull keep external component count low. However, these pull will force current corresponding switch closed. Therefore power down measurements whole transmitter board should performed default state with switches OFF.An external interrupt triggered pushing push button interrupt routine outputs (end transmit signal) AS3902 into standby mode brings power down mode.In this state current consumption entire transmitter demonstration board less that (Under condition that switches state.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Operation Instructions
demonstration board equipped with lithium cell full standalone operation. jumper across amperemeter connector additional jumper across pins Vbat start operation. Transmission starts immediately mode selected switch setting. This because both AS3902 perform entering active state. transmission interrupted time operating push button which triggers interrupt transmission cycle starts when push button pressed. During initialization phase reads mode data rate settings given switch finally enters desired mode. Please note that changes made switch setting only effective after Power Down Power sequence.
Typical Measurements
following gives some typical measured spectra radiated AS3902 demonstration board. These measurements have been performed general laboratory environment specifically suited calibrated radiation measurement. However, care been taken keep transmission path during specific measurement constant possible. Therefore given measurement examples claim give absolute power levels. intention rather give relative measure spectral distribution radiated energy. Actual power levels depend strongly characteristic application specific antenna design.
Figure Narrow band output spectrum AS3902 modulated with 101.-data pattern kbit/s.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Figure Narrow band output spectrum AS3902 modulated with pseudo random data kbit/s.
Figure Modulation bandwidth AS3902 kbit/s measured close ETSI 220-1 recommendation wide-band equipment, clause 8.6.(Only difference: 5kHz used instead kHz). From 220-1 modulation bandwidth defined frequency difference between points wherein power level above dBm. Therefore bandwidth value dependent E.I.R.P. should within band limits. marker settings correspond limits band.
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Figure Spurious emissions AS3902 measured close ETSI 220-1 recommendation wide-band equipment, clause 8.7, without modulation, transmitting constant "H". (Only difference: used instead kHz). highest spurious emissions generated carrier distance 3.39 clock frequency). 220-1 specifies absolute level E.I.R.P. spurious emissions. This limits maximum E.I.R.P. transmitter using AS3902 about dBm. Measurement performed over free-space link using HL040 antenna reception.
Figure Demodulated wave 101.- data pattern 32kbit/s (linear scale).
Rev. March 2001
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Demonstration Board AS3902 Band Transmitter AN3902-002 Application Note
Related Standards References
AS3902 433MHz band transmitter data sheet. 220-1 "Electromagnetic compatibility Radio spectrum Matters (ERM); Short range devices; Technical characteristics test methods radio equipment used 1000 frequency range with power levels ranging Part Parameters intended regulatory purposes. Fujimoto, "Small Antennas", 1987, JOHN WILEY SONS INC., ISBN 91413
Michael MICU-BUDISTEANU Application Engineer Schloss Premstaetten A-8141 Unterpremstaetten AUSTRIA Tel: +43-(0)3136-500-364 FAX: +43-(0)3136-500-693 E-Mail:
Copyright 2000, Austria Mikro Systeme International 8141 Austria. Tel.: +43-(0)3136-500-0, Fax: +43-(0)3136-52501, E-Mail: info@amsint.com rights reserved. part this publication reproduced, stored retrieval system, transmitted, form means, without prior permission writing copyright holder. best knowledge, Austria Mikro Systeme International asserts that information contained this publication accurate correct.
Rev. March 2001
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