Novel IQ imbalance and offset compensation techniques for quadrature mixing radio transceivers

Despite the advantages that quadrature mixing offers to radio front-ends, its practical use has been limited due to its sensitivity towards gain and phase mismatches between its in-phase and quadrature channels. DC offsets are also a problem when a zero-IF transceiver topology is used. In this paper, novel digital compensation techniques are introduced to extract and correct the quadrature imbalances (gain and phase errors), as well as any offset errors that may exist in the quadrature mixing front-end of the modulator or demodulator. The techniques developed in this paper are not based on iterative search techniques, but rather use spectral measurements to extract the imbalance and offset errors directly. Simulation results show that the imbalance and offset errors of the modulator and demodulator can be suppressed to the noise floor of the transceiver, thus enabling the practical the use of quadrature mixing front-ends.