Statistical error shaping for mismatch cancellation in complex bandpass delta-sigma modulators

A new technique using switched capacitors is proposed for shaping component mismatch error in the real and imaginary paths of a complex filter and its effects are illustrated via simulations. Complex filters provide improved performance over a pair of real bandpass filters of the same order. This is possible due to elimination of redundant conjugate pairs of poles and zeros in its noise and signal transfer function. Advantages of using complex filters are clearly seen in such applications as bandpass delta-sigma modulators, used in the conversion of narrowband quadrature IF (intermediate frequency) cellular signals.