One-tap wideband I/Q compensation for zero-IF filters

The I/Q imbalance is one of the performance bottlenecks in transceivers with stringent requirements imposed by applications such as 802.11a. The mismatch between the frequency responses of two analog low-pass filters, used, e.g., for channel selection in zero-IF receivers, makes this I/Q imbalance frequency dependent. Usually, frequency-dependent I/Q mismatch is estimated and corrected by adaptive techniques, which are complex to implement and may converge slowly due to noise. In this work, a simple, delay-based I/Q compensation scheme is proposed based on an extensive statistical analysis. Its digital implementation uses only two coefficients, which are tuned by a one-step two-tone error estimation. Simulations show that this hardware-efficient scheme significantly reduces the I/Q imbalance.