Introduction W2020B Transmitter Architecture. Image Filter Verifying P

The Datasheet Archive - 100 Million Datasheets from 7500 Manufacturers.

Introduction W2020B Transmitter Architecture. Image Filter Verifying P

Datasheet Thumbnail

Top Searches for this datasheet

W2020B Transmitter
Introduction W2020B Transmitter Architecture. Image Filter Verifying Performance. Determining Transmitted Phase Accuracy In-Band Modulation Spurs from Modulator. Synthesizer Integrated Phase Noise. Calculating Total Phase Accuracy. Passing Modulation Mask. Intermodulation Example Setting CSP1088 Transmit Drive Level Synthesizer Reference Sidebands W2020B Output Impedance. Transmit Strip Transmit Strip Configuration. Specification Noise Receive Band Phase Phase Wideband Noise Filter Requirements. Miscellaneous Design Measurement Tips Transmitter Printed-Circuit Board Layout Providing Signals. Measuring Phase Amplitude Imbalance. Measuring Wideband Noise Transmit Strip Using Lucent Technologies W2020B Evaluation Board Appendix. Mathematical Model Modulator
Introduction
W2020B highly integrated transceiver device included Lucent Technologies Microelectronics Group's hardware platform designed implement frequency bands both EGSM standards. W2020B transceiver been designed conjunction with CSP1088 (radio interface device) DSP1618 (digital signal processor) provide complete cellular solution. adding external low-noise amplifier (LNA), power amplifier, filters, complete radio channel realized.
W2020B Transmitter
W2020B Transmitter Architecture
W2020B transmit section consists direct-up modulator shown Figure on-chip voltage controlled oscillators (VCO) provide necessary signals frequency translation. external local oscillators required. oscillator, synthesizer, programmable from 1032 increments. other oscillator fixed oscillator. final transmitted carrier, local oscillator, generated offset mixer; mixes output with synthesizer output. offset mixer architecture prevents pulling, since final transmitted frequency different from that on-chip oscillators.
TIPI (PIN TINI (PIN
SYNTHESIZER MHz-1032
BUFFER
TRFO MHz-915 (PIN
OFFSET MIXER (PIN
QINI (PIN QIPI (PIN (PIN MODULATOR
EXTERNAL IMAGE FILTER
12-3309
Figure W2020 Transmitter Architecture with mixer, offset mixer will produce main products, MHz. desired product MHz. unwanted product, MHz, attenuated image filter, which external parallel resonant band-pass filter with center frequency MHz. filter will present high impedance desired signal impedance unwanted signal. Since this filter differential configuration, common-mode noise that could introduced these external pins (TF1 will rejected. image-filter design guidelines, Image Filter section below. wanted signal, MHz, passed modulation stage. (For in-depth explanation modulator, refer section Mathematical Model Modulator page Appendix. output modulation stage passed through buffer stage. This buffer provides output power into load. output stage operates over compression, which provides greater immunity varying load impedance filter. output level also matches input range following stage (most likely compressed preamplifier) strip.
Image Filter
W2020B architecture consists direct-up modulator with offset mixer. offset mixer mixes synthesizer output with fixed local oscillator output. with mixer, this stage will generate multiple spurious signals. dominant signals MHz. wanted carrier frequency (i.e., 1018 MHz). unwanted mixing product, (i.e., 1018 1135 MHz), must filtered. Lucent Technologies Inc.
W2020B Transmitter
Image Filter
(continued)
TVS1 (PIN (PIN
(PIN
(UHF)
(TXLO)
12-3356
Figure Offset Mixer Circuit Diagram stage subsequent offset mixer phase splitter. phase-splitter circuit operate correctly, image frequency must least below wanted signal. Figure simplified circuit diagram offset mixer. (pins external connection image filter. image filter consists inductor/capacitor parallel resonant circuit. network will resonate wanted frequency, producing high impedance across collectors differential pair wanted frequency (UHF MHz). network will present lower impedance outside passband consequently attenuate signal phase-splitting stage. Figure shows image filter components. filter design, package parasitics also shown.
Lucent Technologies Inc.
W2020B Transmitter
Image Filter
(continued)
12-3310
Figure Image Filter with Package Parasitics Model components Figure include: package lead inductance (0.35 package capacitance (0.5 board trace capacitance (0.3 parasitic capacitance (0.3 Below list design guidelines that should followed design this filter: should tolerance. Using devices with high tolerances will cause filter's center frequency vary frequency band. This will cause varying levels wanted unwanted pasted phase-splitter circuit across channels. filter center frequency should nominally between MHz. center frequency designed slightly lower than band. This ensures sufficient image rejection with component tolerances. resonant frequency calculated from formula: where: additional inductance equal from both traces from W2020B pins filter circuit. recommended that this length short possible equal length from combination stray capacitance follows: Board capacitance (0.6 pad) Package capacitance ground each lead) Additional capacitance inductor capacitance parasitic capacitance series board trace. 0.35 0.35 filter should between high, response will flat across band. defined LS)(C
Lucent Technologies Inc.
W2020B Transmitter
Image Filter
where:
(continued)
equivalent parallel resistance internal resistance external filter. internal resistance 1200 derived from internal resistors (see Figure external portion parallel equivalent series resistance inductor. This approximately 2000 combined series resistance less than Thus: 1200 2000 capacitive inductive reactance (They equal resonance.) Note: this case source load impedance fixed, optimum attained when inductor small value capacitor large value decreased). However, using value will generate high circuit. combined effect component tolerance high circuit could result passband image filter narrower than band. using component values layout Lucent Technologies W2020 evaluation board, resonance calculated: (6.8 nH)(3.3
1200 2000 860e6 6.9e-9
Verifying Performance
image filter improperly designed, unwanted mixing product will filtered. This will allow both high mixing product present following stage modulator, which phase splitter. Having both large signals (UHF MHz) present will cause phase-splitting circuit perform correctly. error phase splitter will degrade rejection unwanted sideband. (See Mathematical Model Modulator section Appendix.) Cancellation sideband (-35 from wanted) across frequency band good indication that image filter properly designed. Another indication that image filter designed correctly measure image spurious W2020B output (UHF MHz) both ends transmit bands. desired carrier amplitude should remain constant while image should attenuated least benchmark, Lucent Technologies evaluation board achieves image rejection.
Determining Transmitted Phase Accuracy
four main contributors phase inaccuracy are:
CSP1088 phase inaccuracy In-band modulation spurs from modulator synthesizer double-sideband integrated phase noise double-sideband integrated phase noise
main contributors phase inaccuracy associated directly with W2020 are:
In-band modulation spurs from modulator synthesizer double-sideband integrated phase noise
These contributors discussed following sections. Lucent Technologies Inc.
W2020B Transmitter
Determining Transmitted Phase Accuracy (continued)
In-Band Modulation Spurs from Modulator
Figure modulator spectrum with 67.7 applied inputs (all ones modulation). There unwanted spurs present output close-in carrier. These spurs caused intermodulation higher-order harmonics that generated within W2020 show multiples baseband frequency. define these spurs follows: Carrier leakage output (UHF MHz) Carrier Baseband frequency Carrier Baseband frequency Carrier Baseband frequency Carrier Baseband frequency Carrier Baseband frequency Carrier Baseband frequency Carrier Baseband frequency Carrier Baseband frequency
These spurs measured with spectrum analyzer usually measured from wanted sideband (USB) output W2020.
CARRIER
Figure W2020B Modulator Spectrum with 67.7 Inputs This section will develop method translating these spurious sidebands into phase-error term degrees RMS. These spurs thought phase amplitude modulation main USB. This visualized vector diagram illustrated Figure vector rotates counter-clockwise direction frequency fUSB. vector rotates slightly higher frequency than USB, rotates slightly lower frequency.
Lucent Technologies Inc.
W2020B Transmitter
Determining Transmitted Phase Accuracy (continued)
RESULTANT INSTANTANEOUS VECTOR PORTION
PORTION
Figure Error Vector Diagram
phase modulation portion dotted line that perpendicular USB. amplitude modulation portion that parallel USB. Since transmit strip fully compressed, assumed that amplitude modulation will rejected. In-band spurs also caused poor power-supply decoupling. Without proper decoupling power supplies W2020, and/or signals could modulated with transmitted signal. Since power supply-decoupling board layout could frequency dependent, necessary measure performance W2020 different baseband frequencies. Measurements three frequencies-10 kHz, kHz, 67.7 kHz-are recommended test modulator performance. These three points given weighting factor probability that frequency occurring random sequence. weighting factors kHz, 67.7 kHz. Table displays list spurious levels, measured dBc, three baseband frequencies. list includes data shown Figure 67.7 frequency. Table Spurious Level dBc) from Wanted Sideband Freq 67.7 -58.8 -56.9 -56.1 -49.8 -48.5 -48.4 -49.5 -47.3 -41.7 Carrier -47.9 -45.6 -45.7 -47.8 -47.2 -45.9 -49.4 -47.0 -41.6 -50.0 -48.9 -48.3 -59.2 -60.0 -56.9
above levels converted relative voltages using conversion: Relative Voltage 10(dBc/20) results shown Table Table Spurious Level Relative Voltage from Wanted Sideband Freq 67.7 e-03 e-03 e-03 Carrier e-03
4.1e-03 3.4e-03 3.2e-03 1.1e-03 4.4e-03 4.5e-03 3.6e-03 1.0e-03 5.1e-03 8.3e-03 3.8e-03 1.4e-03
1.4e-03 3.8e-03 4.3e-03 5.2e-03 1.6e-03 3.8e-03 8.2e-03 5.2e-03
Complementary spurs defined (Carrier U2), (LSB U3), U4), U5). assumed that phase relationships between these vectors produce worst-case situation; that they produce peak-phase error equal vectors. phase error from peak error, take complementary spurs divide results shown Table example, first item under comes from (1.1e-03 1.1e-03) taken from columns Table Lucent Technologies Inc.
W2020B Transmitter
Determining Transmitted Phase Accuracy (continued)
Table Complementary Spurious Level Radians Freq 67.7 1.59e-03 1.72e-03 2.12e-03 4.51e-03 5.20e-03 5.41e-03 4.76e-03 6.21e-03 1.17e-02 Carrier 5.73e-03 6.81e-03 7.25e-03
Comparing numbers useful gaining insight into source phase error. example, kHz, error dominated Carrier whereas 67.7 error dominated Next, find total error term each frequency taking root-squared complementary spurs. example, kHz, Error (1.59e-03)2 (4.51e-03)2 (4.76e-03)2 (5.73e-03)2 8.85e-03
Repeating this each baseband frequency yields error spurious signals, summarized Table Table Weighted Error Spurious Level Freq Weight 0.23 0.28 0.49 Error 8.85e-03 1.07e-02 1.49e-02 Weight (Error) 1.80e-05 3.22e-05 1.09e-04
total phase error modulation spurs found taking square root numbers right-most column Table Radians converted degrees multiplying radians 180°/. Total Error 1.80e-05 3.22e-05 1.09e-04 1.60e-04 radians 180°/ 0.724°
spurs vary with baseband frequency, then error easier calculate: Phase Error 0.7071 U5)2 U4)2 (LSB U3)2 U2)2
where etc., expressed relative voltages Table
Synthesizer Integrated Phase Noise
Figure plot single-sideband close-in phase noise synthesizer. This measurement taken output modulator therefore includes fixed phase noise. Band-power markers used integrate noise power from kHz.
Lucent Technologies Inc.
W2020B Transmitter
Determining Transmitted Phase Accuracy (continued)
Figure Synthesizer Close-In Phase Noise result expressed milliradians, which converted degrees multiplying 180°/: 21.731 mradians (180°/) 1.24° 1.24° must converted double-sideband integrated phase noise. convert measurement DSB, multiply 1.24° 1.76°
(See W2020B Application Note further description phase noise VCO.)
Calculating Total Phase Accuracy
calculate phase error W2020 transmitter, combine basis phase error modulation spurs, phase error CSP1088 signals. example, combined integrated phase noise synthesizer 1.76°, phase error modulation spurs 0.724°, typical phase error CSP1088 0.5°, total would (0.5) (1.76) (0.724)2 1.97° Figure measured constellation diagram error table summary taken from W2020B with random modulation using 89441 vector signal analyzer. This figure indicates total phase error 1.98°, which agrees with above calculated result 1.97°. There slight frequency error term non-coherent clocks reference W2020B measurement equipment.
registered trademark Hewlett-Packard Company.
Lucent Technologies Inc.
W2020B Transmitter
Determining Transmitted Phase Accuracy (continued)
Figure Demodulated Transmitted Signal
Passing Modulation Mask
previous section defined spurious outputs from modulator. This section will explain spurious signals also reference sidebands could cause failure modulation mask.
Intermodulation Example
third-order product that generated from reverse-modulated third harmonic upper sideband mixing with second harmonic example, carrier channel MHz. frequency 67.7 kHz, upper sideband would generated 900.0677 MHz. third harmonic would 2699.7 MHz. Mixing this strong signal with second harmonic would generate frequency: 2699.7969 900) 2699.7969 1800 899.7969 Previously, were defined complementary spurs. That when upper sideband passed through compressed stage such will generated. above example, would appear 900.0677 (900.0677 899.7969) 900.3385 MHz. this frequency, spur must below pass modulation mask. previous version W2020, W2020A, vulnerable inconsistent loading interstage filter. This varying load impedance seen W2020A would cause output stage produce unpredictable levels alleviate effect improper loading filter, recommended that drive level into W2020A reduced mVp-p. Since third-order product, reducing drive will cause drop much faster rate than wanted sideband. W2020B remedied this vulnerable impedance variations. output stage W2020B highly compressed susceptible load variations. ensure W2020B direct replacement W2020A, W2020B production tested with reduced drive level mVp-p. Therefore, recommended that level W2020B mVp-p final application. output power W2020B will remain constant with drive levels from mVp-p Vp-p. Lucent Technologies Inc.
W2020B Transmitter
Passing Modulation Mask (continued)
Setting CSP1088 Transmit Drive Level
CSP1088 conversion signal processor provides drive level Vp-p. also provides common-mode voltage needed bias inputs W2020. Figure input circuit diagram W2020. on-chip resistor capacitor used low-pass network provide filtering input noise.
TVS1 (PIN
INPUTS
(PINS 47-50)
MODULATOR MIXER
12-3355
Figure Input Circuit Diagram
Figure diagram off-chip resistor divider network that recommended drive level mVp-p. This network will attenuate amplitude affect common-mode voltage.
OFF-CHIP INPUTS FROM CSP1088 TINI (PIN
12-3311
TIPI (PIN
ON-CHIP
Figure Recommended Resistor Divider Network from CSP1088 Figure on-chip resistor. on-chip capacitor. off-chip voltage divider resistors (4.42 mVp-p). off-chip voltage divider resistor (21.5 mVp-p).
Lucent Technologies Inc.
W2020B Transmitter
Passing Modulation Mask (continued)
simplified equivalent circuit differential inputs shown Figure parasitic capacitance (board, trace, etc.).
OFF-CHIP INPUT FROM CSP1088 R2/2 2*CC TIPI ON-CHIP
12-3312
Figure Simplified Resistor Divider Input Circuit with Parasitics compute output voltage level, simplified formula R2/2 R2/2
used. However, compute phase error, reactive components must also considered computation. combined board trace parasitics (CB), resistor divider R2), on-chip resistor capacitor combine create low-pass network. pole low-pass network frequency, will cause phase distortion signals. Analysis circuit Figure shows that long values sufficiently small (such values 4.42 21.5 used above), then phase error will negligible.
Synthesizer Reference Sidebands
W2020B designed using reference frequency. loop-filter printed-circuit board design affect level (and higher harmonics i.e., kHz) sidebands that present signal. This application note will discuss cause reference sidebands will point that they could cause failure modulation mask. (Refer W2020 Circuits Application Note.) Figure spectrum (all ones modulation) with poor reference sidebands. This plot produced connecting resistor from phase-locked loop (PLL) filter power supply. power supply voltage adjusted force lock. tries reestablish lock unable because external power supply keeps varactor voltage constant. effect caused presence reference sidebands. Since these sidebands originate from they will pass through mixers modulator modulated. This sidebands appear from wanted sideband.
Lucent Technologies Inc.

Introduction W2020B Transmitter Architecture. Image Filter Verifying P

Top Searches for this datasheet

Other recent searches