Analysis of higher-order N-tone sigma-delta modulators for ultra wideband communications

We consider the properties of a class of non-oversampling N-tone sigma-delta modulators which have applications in the design of UWB-OFDM communications systems. The spectrum gaps that exist in such systems are well-matched to the noise shaping properties of these modulators and their non-oversampling nature makes them practical for use with these ultra wideband signals. Performance results for first-order, second-order and L^th-order modulators are presented, and a general expression for the excess resolution that can be gained in such systems is obtained.