Multibit quadrature sigma-delta modulator with DEM scheme

A simple dynamic element matching (DEM) scheme for sampled data systems is presented. The scheme is suitable for switch-capacitor (SC) or switch-current circuits. The DEM scheme eliminates the mirror spectral image around +/-F_s/4, where F_s is the sampling frequency, while generally introducing a more benign self-image. The scheme is suitable for quadrature SC band-pass(BP) ΣΔ modulators with a centre frequency at F_s/4 or $F_s/4, where it can minimize the quantization noise mirror image and where the signal mirror image can be suppressed. Furthermore, a quadrature mismatch noise shaping method that can be used with this DEM scheme is introduced.