Complex mismatch shaper for tree-structured DAC in multi-bit complex sigma-delta modulators

A multi-bit sigma-delta (SigmaDelta) modulator is an attractive solution for a high-resolution analog-to-digital conversion. In multi-bit complex SigmaDelta modulators, the overall resolution of the modulator is limited by the mismatch errors in the digital-to-analog converters (DACs) of the I/Q-paths. The mismatch in the DAC bank causes unwanted additional noise power in passband. In this paper, a first-order complex mismatch shaper, which is based on a complex noise shaping technique, is presented for the reduction of a mismatch effect in the feedback multi-bit DACs of the complex SigmaDelta modulator. From the purpose of mismatch shaping, the complex mismatch shaper should have the same intermediate frequency as the modulator. The proposed complex mismatch shaper can be applied to the tree-structured element selection logic (ESL). Finally, the effectiveness of the proposed mismatch shaper is proved by simulation.