Performance analysis of low oversampling ratio sigma-delta noise shapers for RF applications

Baseband signal processing for current base stations or 3rd generation mobile systems will impose high bandwidth and high VLSI integration demand. Many of the desired integration aspects can be satisfied with sigma-delta converter front-ends. However, under the technology constraints there are simultaneous requirements for high sample rate and low oversampling ratio in order to achieve the desired baseband width. In this paper, we present system architecture results for 4th-order cascaded noise shaper architectures for baseband front-ends and show that the cascaded structures with proper scaling will satisfy simultaneous demand on linearity (spurious free dynamic range) and high SQNR with low oversampling ratio based on usage of multibit quantizers outside the actual signal noise shaping path