Compensation technique for impairments of wideband quadrature demodulators for direct conversion receivers

This paper describes a compensation technique for the gain/phase imbalance of quadrature demodulators for direct conversion receivers. In this compensation method, the power measurements for the imbalance estimation can be done in less than ten symbol periods of the test signals. This means that our compensation method does not need as many iterative cycles using the least mean square method or discrete Fourier transformation required by previous methods. Experimental results show that the differences between the estimated and actual values are small: the gain imbalance was less than 0.35 dB, and the phase imbalance was less than 1.2°.