Power amplifier linearisation using digital predistortion and multi‐port techniques

Abstract

Power amplifiers are essential components in communication systems and are inherently non-linear. The non-linearity creates spectral growth (broadening) beyond the signal bandwidth, which interferes with adjacent channels. It also causes distortions within the signal bandwidth, which decreases the bit error rate at the receiver. This study reports an adaptive digital predistorter with fast convergence rate and low complexity and cost to alleviate these problems. In this design, a lookup table-based adaptive digital predistortion (DPD) technique using a five-port receiver instead of traditional heterodyne and homodyne architectures is proposed to realise the linearisation loop for this amplifier. The five-port receiver is implemented by use of passive microwave circuits and detector diodes. This approach highly reduces the cost and complexity of the linearisation system. Simulation and measurement results obtained are presented for a laterally diffused metal–oxide–semiconductor-based high-power amplifier biased in class AB operation with wideband code-division multiple access input signal to demonstrate the effectiveness of this novel DPD design. Moreover, these results are compared with DPD technique using homodyne receiver in feedback path.