TH71102

315/433MHz

FSK/FM/ASK Receiver

TH71102 Data Sheet

Page 2 of 20

Nov. 2001

3901071102

Rev. 005

General Description

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

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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)

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Low-noise amplifier (LNA) for high-sensitivity RF signal reception

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First mixer (MIX1) for down-conversion of the RF signal to the first IF (IF1)

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second mixer (MIX2) for down-conversion of the IF1 to the second IF (IF2)

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IF amplifier (IFA) to amplify and limit the IF2 signal and for RSSI generation

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Phase coincidence demodulator (DEMOD) with third mixer (MIX3) to demodulate the IF signal

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Operational amplifier (OA) for data slicing, filtering and ASK detection

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Bias circuitry for bandgap biasing and circuit shutdown

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 demodu-

lator can be constituted either by a ceramic resonator or an LC tank (optionally with a varactor diode to create

an AFC circuit). In ASK configuration, the RSSI signal is feed to an ASK detector, which is constituted by the

operational amplifier.

Demodulation

Type of receiver

FM / FSK

narrow-band RX with ceramic demodulation tank

FM / FSK

wide-band RX with LC demodulation tank

ASK

RX with RSSI-based demodulation

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 frontend filter. Efficient RF frontend 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 RXICs have the same die. At the

TH71101 the second mixer MIX2 operates as an amplifier.