A novel technique for gain/phase error cancellation in LINC transmitters

Linear amplification with non-linear components (LINC) is a promising linearisation technique for improving power amplifier efficiency in radio transmitters. In this paper we present a novel technique for correcting the gain/phase errors inherent in LINC transmitters. The technique employs a feedback signal to generate an error signal with the aid of a reference-modulated signal. A direct search algorithm is used to estimate the gain/phase imbalance between the two amplifying branches for correction. A computer simulation model is used to verify the validity of the technique. Simulation results indicate out-of-band radiation suppression up to 15 dB for a gain imbalance of 1 dB. The performance of the technique with various modulation methods has been investigated and shown to work favourably with QPSK and GMSK modulated signals.