New methods for adaptation of quadrature modulators and demodulators in amplifier linearization circuits

Imperfections in analog quadrature modulators (QM's) and demodulators-gain and phase imbalance and de offset-have a devastating effect on amplifier linearization circuits. Correction circuits have a simple structure, but their parameters must be adjusted adaptively, This paper introduces two new methods for such an adaptation, The first is based on a training sequence consisting of a tone at one or more amplitudes, and the second needs no training sequence at all, They are faster and more robust than previously published methods.