EVB71102
315/433MHz Receiver
Evaluation Board Description
1
Theory of Operation
1.1 General
With the TH71102 receiver chip, various circuit configurations can be arranged in order to meet a number of
different customer requirements. For FM/FSK reception the IF tank used in the phase coincidence
demodulator can also be constituted by a ceramic discriminator with a varactor diode to create an AFC
circuit. In ASK configuration, the RSSI signal is fed to an ASK detector, which is constituted by the
operational amplifier.
The superheterodyne configuration is double conversion where MIX1 and MIX2 are driven by the internal
local oscillator signals LO1 and LO2, respectively. This allows a high degree of image rejection, achieved in
conjunction with an RF front-end filter. Efficient RF front-end filtering is realized by using a SAW, ceramic or
helix filter in front of the LNA and by adding an LC filter at the LNA output.
A single-conversion variant, called TH71101, is also available. Both Receiver ICs have the same die. At the
TH71101 the second mixer MIX2 operates as an amplifier.
The TH71102 receiver IC consists of the following building blocks:
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PLL synthesizer (PLL SYNTH) for generation of the first and second local oscillator signals LO1 and LO2,
parts of the PLL SYNTH are: the high-frequency VCO1, the feedback dividers DIV_8 and DIV_2,
a phase-frequency detector (PFD) with charge pump (CP) and a crystal-based reference oscillator (RO)
Low-noise amplifier (LNA) for high-sensitivity RF signal reception
First mixer (MIX1) for down-conversion of the RF signal to the first IF (IF1)
Second mixer (MIX2) for down-conversion of the IF1 to the second IF (IF2)
IF amplifier (IFA) to amplify and limit the IF2 signal and for RSSI generation
Phase coincidence demodulator (DEMOD) with third mixer (MIX3) to demodulate the IF signal
Operational amplifier (OA) for data slicing, filtering and ASK detection
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Bias circuitry for bandgap biasing and circuit shutdown
1.2 EVB Technical Data Overview
! Input frequency range: 260 MHz to 510 MHz
! Power supply range:2.3 V to 5.5 V @ ASK
2.7 V to 5.5 V @ FSK
! Range of first IF2: 400 kHz to 22 MHz
! Maximum input level:-10 dBm @ ASK
0 dBm @ FSK
! Temperature range: -40 °C to +85 °C
! Standby current: 50 nA
! Operating current: 6.5 mA @ low gain mode
8.2 mA @ high gain mode
! Sensitivity: -110 dBm @ ASK 1)
-104 dBm @ FSK 2)
! Range of first IF1: 10 MHz to 80 MHz
! Image rejection: > 65 dB (e.g. with 433.92 MHz
SAW front-end filter and at 10.7 MHz IF2)
! Spurious emission: < -70 dBm
! Input frequency acceptance range: up to
! RSSI range: 70 dB
±100 kHz
! FM/FSK deviation range: ±2.5 kHz to ±80 kHz
! Maximum analog modulation frequency: 15 kHz
1) at 4 kbps NRZ, BER = 3⋅10-3, 180 kHz IF filter BW, incl. 3 dB SAW front-end-filter loss
2) at 4 kbps NRZ, BER = 3⋅10-3, ± 20 kHz FSK deviation, 180 kHz IF filter BW, incl. 3 dB SAW front-end-
filter loss
For more detailed information, please refer to the latest TH71102 data sheet revision
39012 71102 01
Rev. 011
Page 3 of 14
EVB Description
June/07
MELEXIS [ Melexis Microelectronic Systems ]
