Recent developments in integrated receiver
design for digital cellular applications favor more of the channel
filtering function performed at baseband or low-IF rather than at the
intermediate frequencies of traditional superheterodyne receivers. This
facilitates greater levels of integration and back-end digital signal
processing for demodulation and symbol decoding.
This thesis documents the design of a
cascaded biquad switched-capacitor (SC) baseband channel filter for a
GSM digital cellular mixed-mode receiver IC used in a base station
application. It was fabricated in 0.8 µm BiCMOS, and performance
is characterized against theoretical and simulated response. The filter
corner frequency is programmable up to 200 KHz at a 20-times
oversampling ratio. Measured and simulated corner frequency accuracy is
within one percent of the programmed value. The area consumed by the
baseband filter is 1765 square mils, and power consumption is 26 mW per
channel. The IC containing this baseband filter is now in commercial
pilot production.
