Blind Frequency-Selective I/Q Mismatch Compensation Using Subband Processing

This brief proposes a new approach to frequency-selective in-phase (I)/quadrature (Q) mismatch compensation, based on subband processing: The spectrum of the signal received by the digital baseband processor-a combination of wanted and image signals-is split into subbands so that, within each subband, the I/Q mismatch can be considered constant with respect to frequency. Therefore, standard compensation algorithms, devised for frequency-invariant I/Q mismatch, can be applied to compensate the signal within each subband; finally, the outputs of each subband processing path are recombined to yield the wanted signal. This procedure is demonstrated by a case study that describes an I/Q mismatch compensation algorithm particularly well suited for the proposed method and proves that, at least for certain I/Q imbalances, the efficiency of compensation can be significantly improved even if only a small number of subbands are employed. The resulting frequency-selective I/Q mismatch compensation solution is suitable for wideband multistandard receivers.