AD6432中文资料GSM 3 V Transceiver IF Subsystem数据手册ADI规格书

描述 Description

The AD6432 IF IC provides the complete transmit and receiveIF signal processing, including I/Q modulation and demodulation,necessary to implement a digital wireless transceiver suchas a GSM handset. The AD6432 may also be used for otherwireless TDMA standards using I/Q modulation.The AD6432's receive signal path is based on the proven architectureof the AD607 and the AD6459. It consists of a mixer,gain-controlled amplifiers, integrated roofing filter and I/Qdemodulators based on a PLL. The low noise, high-interceptvariable-gain mixer is a doubly-balanced Gilbert-cell type. It hasa nominal -13 dBm input-referred 1 dB compression point anda 0 dBm input-referred third-order intercept.The gain-control input accepts an external control voltage inputfrom an external AGC detector or a DAC. It provides an 80 dBgain range with 27.5 mV/dB gain scaling, where the mixer andthe IF gains vary together.The I and Q demodulators provide inphase and quadraturebaseband outputs to interface with Analog Devices' AD7015and AD6421 (GSM, DCS1800, PCS1900) baseband converters.An onboard quadrature VCO, externally phase-locked tothe IF signal, drives the I and Q demodulators. The quadraturephase-locked oscillator (QPLO) requires no external componentsfor frequency control or quadrature generation, and demodulatessignals at standard GSM system IFs of 13 MHz, or26 MHz with a reference input frequency of 13 MHz; or, ingeneral, 1X or 2X the reference frequency. Maximum referencefrequency is 25 MHz.This reference signal is normally provided by an externalVCTCXO under the control of the radio's digital signalprocessor. The transmit path consists of an I/Q modulatorand buffer amplifier, suitable for carrier frequencies up to300 MHz and provides an output power of -17.5 dBm ina 50 Ohm system. The quadrature LO signals driving theI and Q modulator are generated internally by dividing bytwo the frequency of the signal presented at the differentialLO port of the AD6432. In both the transmit and receivepaths, onboard filters provide 30 dB of stopband attenuation.The AD6432 comes in a 44-lead plastic thin quad flatpack(TQFP) surface mount package.