A 4TH ORDER BANDPASS DELTA-SIGMA-MODULATOR WITH DIGITALLY PROGRAMMABLE PASSBAND FREQUENCY

The design and implementation of a fourth order switched-capacitor ban dpass delta-sigma modulator with digitally programmable passband is de scribed. The quantization noise null can be programmed from 0.4 pi (0. 2f(s)) to 0.6 pi (0.3f(s)) in steps of 0.01 pi (f(s)/200) by changing digital switch settings. This design enables the A/D conversion of a b andpass signal with digital tuning of the center frequency for applica tion in systems such as a transceiver IF stage. The modulator IC measu res 4.8mm(2) in a 2 mu m CMOS process and achieves an SNR of 47 and 59 dB over a 0.01n bandwidth at sampling rates of 2.358 MHz and 1.25 MHz , respectively.