Adaptive correction of errors in second-order MASH /spl Delta//spl Sigma/FDM solution

In many communication applications, it is necessary to demodulate and digitize frequency or phase modulated signals. This paper presents a new, adaptive improvement to a novel second-order frequency-to-digital cascaded delta sigma modulator. The adaptive corrections significantly reduce the sensitivity to analog imperfections in the MASH-like /spl Delta//spl Sigma/ frequency-to-digital modulator, and makes it possible to implement the circuit in standard digital CMOS without loosing performance. The result is a simple second-order delta-sigma modulator with high precision. Simulations of the circuit with errors and corrections are included to confirm the theory.