Non-iterative compensation for software-defined radio quadrature front-end inaccuracies

The analog front-end of a software-defined radio (SDR) transceiver can have a critical impact on the accuracy of the transmitted and received signals. This paper proposes a digitally compensated direct-conversion front-end for both the transmission and reception stage. Quadrature mixing impairments are studied from first principles, and the exact relationships between quadrature front-end impairments and signal artefacts are derived. It is shown that these impairments may be substantially suppressed by simple digital techniques that directly estimate compensation parameters from measurements, allowing non-iterative compensation. Finally, these techniques are verified by practical experiments.