Patent ID: 8325794
Filing Date: 2012-12-04
Classification: H03D

Abstract:
1. An apparatus for calibrating IQ mismatch so that an in-phase oscillating signal and a quadrature-phase oscillating signal are orthogonal to each other, the calibration apparatus comprising: a phase detection module for detecting the in-phase oscillating signal and the quadrature-phase oscillating signal to generate a low frequency signal indicating a phase difference between the in-phase oscillating signal and the quadrature-phase oscillating signal in an analog domain; a calculating unit for generating a control signal in the analog domain according to the low frequency signal, wherein if a magnitude of the low frequency signal is within a first range, the calculating unit raises a voltage level of the control signal, if the magnitude of the low frequency signal is within a second range, the calculating unit reduces the voltage level of the control signal, and the first range and the second range do not overlap, and wherein if a number of consecutive times that the magnitude of the low frequency signal travels back and forth between the first range and the second range exceeds a predetermined value, the calculating unit stops changing the control signal; and a phase adjusting module coupled to the calculating unit for adjusting the phase of at least one of the in-phase oscillating signal or the quadrature-phase oscillating signal according to the control signal so that the in-phase oscillating signal and the quadrature-phase oscillating signal are orthogonal to each other while maintaining respective frequencies of the in-phase oscillating signal and the quadrature-phase oscillating signal in the analog domain.