Time Domain Blind I/Q Imbalance Compensation Based on Real-Valued Filter

This paper proposes a novel time domain blind compensation for frequency-independent and frequency-dependent I/Q imbalance in direct-conversion receivers. Analysis of a difference filter representing the frequency-dependent I/Q imbalance shows that the filter taps are tightly constrained by analog front-end image attenuation (IA). For practical front-ends with reasonable IA, it is proved that the difference filter is minimum phase. We also show that the magnitude response of the difference filter can be obtained from the branch signal autocorrelations. Then, the magnitude response can be used to determine the corresponding minimum phase response. Subsequently, from the cross-correlation of the branch signals, we can estimate the frequency-independent phase imbalance. Since the proposed method has an analytical solution, it can be easily implemented. Simulations of various scenarios confirm its validity and its superior compensation performance.