A 450kHz CMOS Gm-C bandpass filter with±0.5 center frequency accuracy for on-chip PDC IF receivers

摘要

A 450kHz Gm-C bandpass filter (BPF) with an on-chip frequency controller for Japanese personal digital cellular (PDC) handsets is implemented in 0.35μm CMOS technology. The controller achieves a ±0.5% accuracy of the center frequency withouttrimming or external components. This accuracy is achieved by directly measuring the center frequency through observations of the filter step response, and by digitally controlling the transconductances of operational transconductance amplifiers (OTAs).The filter is a 16th-order roll-off filter and draws 4.8mk from a 2.5V supply. Use of this filter enables full integration of the intermediate-frequency (IF) module of the PDC handsets on CMOS, because a discrete ceramic filter is unnecessary.