Quadrature ΣΔ modulators with a dynamic element matching scheme

This brief presents a new topology of a multibit quadrature band-pass sigma-delta modulator which employs a simple dynamic element matching (DEM) technique in order to reduce the effects of path mismatch, namely aliasing in the signal band of the mirror images of the signal and of the quantization noise. The DEM scheme results in a reduction of the aliasing of the quantization noise mirror image while it reduces the input signal mirror image alias problem to a self-image problem. It is shown that the self-image can be completely removed in switched-capacitor (SC) implementations by using the same capacitors to sample the input and the reference of the feedback DACs. Moreover, a simple method for extending low-pass mismatch noise shaping techniques to the complex band-pass case is proposed for the case of multibit feedback DACs.