A switched-capacitor quadrature demodulation technique, which is insen
sitive to first-order errors resulting from 90 degrees phase inaccurac
y and path mismatch, is demonstrated to shift a band-pass spectrum dir
ectly to de. A sampling rate of four times the passband center frequen
cy facilitates the quadrature demodulation and removes the 90 degrees
phase error. Furthermore, the path-mismatch error is canceled using th
e same signal path repeatedly, thereby reducing the number of op amps.
A fourth-order band-pass Delta-Sigma modulator, integrated in an area
of 1 mm(2) using 2-mu m CMOS, consumes 0.8 mW with a single 3.3-V sup
ply and exhibits an SNR of 56 dB within a 30-kHz bandwidth.