An analog mismatch calibration system for image-reject receivers

The image-reject receiver is an architecture that ideally passes the desired signal and rejects its image. However, due to mismatches in the signal path, the image-rejection ratio (IRR) achieved in practice is quite limited. This paper presents an analog technique that automatically calibrates phase and gain errors and effectively improves the IRR of image-reject receivers. The feasibility of the calibration scheme is demonstrated by a 2-GHz prototype image-reject receiver design using a Weaver architecture, implemented in a 0.25-μm CMOS technology. With an initial phase and gain mismatches of 5° and 1 dB respectively in the signal path, simulation results show that the calibration process converges very fast and an IRR of 66 dB is achieved after the calibration. Running from a single 2.7-V supply, the calibration system incurs only 9 mW power dissipation.