Phase self-calibrated scheme for zero-IF receiver

Abstract

A new phase self-calibrated scheme maintains the quadrature is proposed in the letter, which mainly includes quadrature phase detector (QPD), charge pump, comparator, controller and variable delay buffer (VDB) etc. The primary idea behind the scheme is that the quadrature phase error is converted to the voltage variation on the capacitor, and then the voltage variation drives the controller to tune the VDB to the proper control word. The phase calibration is digitally controlled and considers the mismatch effect of charge pump, removing the disadvantage of conventional analog calibration circuit whose performance is sensitive to process and temperature variations and aging. It is shown that the two VDBs have an 8°quadrature phase shift tuning range, and an 8 mA current at 1.7 HGz, and the calibration process takes less than 160 μs.