Mismatch cancellation in quadrature bandpass ΔΣmodulators using an error shaping technique

摘要

A technique for shaping component mismatch error in the real and imaginary paths of a complex (quadrature) ΔΣ are studied and simulated. Complex bandpass ΔΣ modulators provide improved performance over a pair of real bandpass ΔΣ modulators of the same order in the conversion of narrow-band quadrature intermediate frequency (IF) signals. This is possible due to elimination of redundant conjugate pairs of poles and zeros in its noise and signal transfer function. Mismatches in the modulators real and imaginary paths, however, results in spectral leakage of image band interference and image band quantization noise to the passband of the converted output. Strategic pole-zero placement, as well as adaptive techniques has been studied in earlier works. The work presented here takes advantage of the inherent dual paths of the complex bandpass ΔΣ modulator to reduce component mismatch effects using a switched capacitor error shaping technique