Harmonic Characterization and Correction of Device Mismatch

摘要

A novel apparatus for and method of harmonic characterization and ratio correction of device mismatch between coarse and fine varactor tuning devices within a segmented unified varactor bank of a radio frequency (RF) digitally controlled oscillator (DCO). The DCO uses a single unified bank of varactors that is divided into an MSB bank, LSB bank and sigma-delta (SD-LSB) bank. Any ratio mismatches between MSBs and LSBs are digitally calibrated out using a DCO step-size pre-distortion scheme wherein the LSB steps are adjusted to account for the ratio mismatch between the MSB/LSB step sizes. A harmonic characterization technique is used to estimate the mismatches in the minimal size CMOS tuning varactors of a digitally controlled RF oscillator (DCO), wherein the nominal ratio mismatch between the MSB and LSB devices is estimated using hybrid stochastic gradient DCO gain estimation algorithms. The nominal ratio mismatch and the mismatches in the MSB and LSB banks are used to determine the average MSB/LSB mismatch. The average mismatch value is then used to correct the LSB steps.