TH71112(2001) 查看數據表（PDF） - Melexis Microelectronic Systems

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TH71112
(Rev.:2001)

868/915MHz FSK/FM/ASK Receiver

Melexis Microelectronic Systems  

TH71112

868/915MHz

FSK/FM/ASK Receiver

General Description

The TH71112 receiver IC consists of the following building blocks:

" 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_16 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 IF1

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

" IF amplifier (IFA) to amplify and limit the IF 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

" Bias circuitry for bandgap biasing and circuit shutdown

With the TH71112 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

FM / FSK

FM / FSK

ASK

Type of receiver

narrow-band RX with ceramic demodulation tank

wide-band RX with LC demodulation tank

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 TH71111, is also available. Both RXICs have the same die. At the

TH71111 the second mixer MIX2 operates as an amplifier.

TH71112 Data Sheet

3901071112

Page 2 of 20

Nov. 2001

Rev. 005

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