Blind Adaptive Compensation of Strong Frequency-Dependent IQ Imbalance for Wideband Direct-Conversion Receivers

In this paper, we propose an adaptive compensation algorithm to reduce the strong frequency-dependent in-phase/quadrature phase (IQ) imbalance in wideband direct-conversion receivers without using training data. Firstly, we propose an frequency-dependent IQ imbalance model by inserting a finite impulse response (FIR) filter to the Q-channel to represent the frequency-dependent characteristics. Subsequently, by using the properness condition as well as the equi-absolute variance condition, we derive a blind frequency-dependent IQ imbalance compensation algorithm based on this model. Finally, simulations with 16-ary quadrature amplitude modulation (16-QAM) signals are conducted, and the results show that even for strong frequency-dependent IQ imbalance, the proposed algorithm still provides impressive performances in correcting distortion and reducing the symbol error rate (SER) as well as the error vector magnitude (EVM).