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

A 450 kHz Gm-C bandpass filter (BPF) with an on-chip frequency controller for Japanese personal digital cellular (PDC) handsets is implemented in 0.35 /spl mu/m CMOS technology. The controller achieves a /spl plusmn/0.58 accuracy of the center frequency without trimming 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 4.8 mA from a 2.5 V 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.