COMPLEX LOW-PASS INTEGRATED ACTIVE FILTER FOR DIRECT CONVERSION TRANSCEIVER FOR WCDMA

Abstract

Direct -Conversion is an alternative wireless transceiver architecture to the well-established super heterodyne, particularly for highly integrated, low power terminals. Direct -Conversion transceivers suffer from the imbalance of the I and Q paths. By using a complex low-pass filter topology instead of a conventional pair of real low-pass filters, this imperfection can be reduced. In this thesis, design of a 3.3V, fifth order complex Chebyshev gm-C low- pass filter for WCDMA transceiver is presented. The filter has a 3-dB cutoff frequency of 2.5 MHz and has been designed in 0.35?m CMOS technology. The designed filter has high input and output linearity, and good noise performance. On -chip automatic frequency tuning circuit has been designed to keep the filter frequency response immune to supply voltage, process and temperature variations. The designed frequency tuning circuit has a tuning error of less than 2%.