EVB71111 Datasheet, PDF(3/14 Page) Melexis Microelectronic Systems – 868/915MHz Receiver Evaluation Board Description

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EVB71111 Datasheet, PDF (3/14 Pages) Melexis Microelectronic Systems – 868/915MHz Receiver Evaluation Board Description

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EVB71111

868/915MHz Receiver

Evaluation Board Description

1 Theory of Operation

1.1 General

With the TH71111 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.

A double-conversion variant, called TH71112, is also available. This receiver IC allows a higher degree of

image rejection, achieved in conjunction with an RF front-end filter. Both RXICs have the same die. At the

TH71112, the second mixer (MIX2) is used to down-convert the first IF (IF1) to the second IF (IF2). At the

TH71111, MIX2 operates as an amplifier.

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.

The TH71111 receiver IC consists of the following building blocks:

# PLL synthesizer (PLL SYNTH) for generation of the local oscillator signal LO, parts of the PLL SYNTH

are: the high-frequency VCO1, the feedback divider DIV_32, 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 IF

# IF pre amplifier which is a mixer cell (MIX2) that operates as an amplifier

# 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

1.2 EVB Technical Data Overview

! Input frequency range: 800 MHz to 930 MHz

! Power supply range: 2.3 V to 5.5 V @ ASK

2.7 V to 5.5 V @ FSK

! Temperature range: -40 Â°C to +85 Â°C

! Standby current: 50 nA

! Operating current: 7.5 mA @ low gain mode

9.2 mA @ high gain mode

! Sensitivity: -109 dBm @ ASK 1)

-103 dBm @ FSK 2)

! Range of IF: 400 kHz to 22 MHz

! Maximum input level: -10 dBm @ ASK

0 dBm @ FSK

! Image rejection: > 45 dB (e.g. with 868.3 MHz

SAW front-end filter and at 10.7 MHz IF)

! Spurious emission: < -70 dBm

! Input frequency acceptance range: up to Â±100 kHz

! RSSI range: 70 dB

! FM/FSK deviation range: Â±2.5 kHz to Â±80 kHz

! Maximum analog modulation frequency: 15 kHz

1) at 4 kbps NRZ, BER = 3â10-3, 180 kHz IF filter BW, incl. 3 dB SAW front-end-filter loss

2) at 4 kbps NRZ, BER = 3â10-3, Â± 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 TH71111 data sheet revision

39012 71111 01

Rev. 011

Page 3 of 14

EVB Description

June/07

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