Towards flexible parallel sigma delta modulator for software defined radio receiver

A novel frequency band decomposition architecture based on a single-bit 4^th order sigma delta modulators and intended for a software defined radio receiver is presented in this paper. The parallel designed architecture is flexible with parallel programmable branches. Synthesis results prove that this architecture satisfies the multistandard receiver specifications without the use of automatic gain control circuit. Nevertheless, system level analysis of the mixed baseband architecture using a single passive anti-aliasing filter has revealed adjacent branch interference problems. A design specification for a non-unitary signal transfer function for sigma delta modulators is proposed to cover interferences of adjacent branches.