Reconfigurable bandpass sigma-delta modulator with programmable NTF for low-IF multi-mode receivers
A new reconfigurable bandpass sigma-delta modulator (BPSDM) structure is proposed for low-IF multi-mode wireless systems. The proposed modulator can be reconfigured to operate in different signal bandwidths and at different signal-to-noise ratios by rearranging and optimizing the order of the noise transfer function of the loop while still maintaining stability. Compared with conventional multi-mode BPSDM, employing cascade structures and multi-bit sub-ADCs, the proposed modulator features many attractive advantages, such as (1) avoiding coefficient mismatch between analog and digital components in cascade structures, (2) avoiding DAC non-linearities that are otherwise introduced by commonly used dynamic element matching techniques, and (3) improving and varying the dynamic range performance while meeting the requirements of different wireless standards.
reconfigurable bandpass sigma-delta modulator multi-mode noise transfer function snr