A fully analog calibration technique for phase and gain mismatches in image-reject receivers

A systematic approach to I/Q mismatch calibration in image-reject receivers is presented in this paper. A new error detection algorithm is proposed, which automatically calibrates for phase and gain mismatches limiting the performance of image-reject receivers. A dual-loop feedback is employed which looks for the minimum phase/gain error using a 2-dimensional analog-based search algorithm and then finds the minimum value for the error. An experimental CMOS prototype RF front-end for cognitive radio applications operating at 400–800 MHz is proposed and simulated in the 0.18 μm CMOS technology, achieving an image rejection ratio (IRR) better than 55-dB in post-layout simulation. The comprehensive mathematical model of this analog algorithm is thoroughly studied in the appendix and the convergence is verified theoretically.