Mismatch-insensitive N-path multirate sigma-delta modulator for high-frequency applications

An N-path multirate Sigma-Delta Modulator (SDM) was recently proposed where the first integrator was implemented using an N-path architecture and a comb filter. The replacement of the first integrator in the N-path structure and the comb filter can relax the speed requirements of the opamps in the first stage and alleviate various mismatch effects. An improved structure for the comb filter is proposed here which eliminates thoroughly the mismatch effects between paths. Analysis and simulations also show that the proposed structure makes the N-path multirate SDM more stable and mismatch insensitive.