IQ imbalance decorrelation in digital array radars

摘要

Digital array radars (DAR) with element-level digital transmission and reception present new opportunities for more advanced radar functionality and performance. In order to reduce RF front-end complexity while also reducing the need for high sample rates, the analog IQ demodulation receiver, or homodyne, is proposed so that only a single local oscillator (LO) is needed per element. An important homodyne receiver architecture impairment is IQ imbalance and its mitigation is the focus of this article. We introduce a new approach to IQ imbalance compensation, which leverages the digital array architecture to decorrelate these errors and significantly reduce their impact at the digital beam-formed output. As a result, we show that the image rejection ratio, defined as the ratio of the desired-signal power level to that of the image after digital beamforming is significantly higher than at any individual channel output. We derive a single compensation factor from the imbalance statistics estimated across all array elements. The compensation technique is then applied to measured data from a 32-element X-band homodyne DAR test bed.