Robust low-complexity blind frequency-dependent I/Q estimation and compensation

A low-complexity blind frequency-dependent I/Q imbalance compensation scheme is proposed based on linear prediction (LP) method. It provides non-iterative processing which reduces computational complexity. No special training sequence is used and I/Q mismatch calibration is performed using any received sequence. Frequency-dependent (FD) I/Q imbalance can be compensated simply by matching the filter responses of the I and Q branches. This is achieved by estimating the inverse impulse responses of the I and Q branches using LP and then finding the ‘difference’ filter that can be used in one of the branches to match the other branch. Using simulations, we show that the proposed method has at least 5–7 dB better image rejection ratio (IRR) performance compared to other blind FD I/Q estimation techniques in the literature, for a realistic mismatch scenarios. Moreover, the computational complexity of the proposed technique is shown to be 20x less than the least complex blind estimation scheme in the literature for an 8-tap compensation filter. Finally, we propose the use of a noise-generator for offline-calibration.