High order cascade multibit σΔ modulator for wide bandwidth applications

A novel 2-1-1 cascaded sigma-delta I/Q modulator suitable for WCDMA applications is presented. The modulator employs multibit quantizer in the last stage and dynamic element matching (DEM) to attain high linearity over a wide band-width at an oversampling ratio (OSR) of 16. The DEM algorithm is introduced in such a way as to suppress in-band digital-to-analog converter (DAC) errors in the feedback of the last stage, thereby enabling the use of the highest resolution quantizer yet reported in a multibit cascaded sigma-delta modulator.