Block-Wise Estimation of and Compensation for I/Q Imbalance in Direct-Conversion Transmitters

This correspondence proposes a new technique for accurate estimation and compensation for I/Q imbalance in modulators and demodulators used in direct-conversion radio transmitters. This technique uses the actual in-phase (I) and quadrature (Q) components of the modulated signals at the input and output of the transmitter-under-test for adaptive determination of the modulator and demodulator complex gain imbalances. The accuracy of the new algorithm is carefully assessed and compared to earlier works. The robustness of the algorithm to a number of common practical implementation issues (group delay, DC offset, propagation delay) are also discussed and demonstrated.