A New Predistorter Design for Nonlinear Power Amplifiers Using the Minimum Distortion Power Polynomial Model (MDP-PM)

The problem of nonlinear amplification in spectrally efficient modulated systems has been well addressed in the literature. Usually the impairment of nonlinear amplification manifest themselves as both the in-band distortion and the adjacent-channel interference. In order to design schemes to combat these nonlinear effects, we need to model the PAs in digital communication systems in sufficiently accurate but simple way. The PAs in most present systems can be described by bandpass nonlinearities. Among various representations of them, the polynomial function has been used extensively because it is mathematically easy to handle and easy to implement in hardware. Conventionally only one polynomial curve is used to fit the measured data according to a given optimal criteria. In [4], a new polynomial model for PAs has been introduced which incorporates the effects of a PA's operating point and its input modulations format. This model is derived based on the criterion of minimizing the average power in the instantaneous error signal between a PA's model and the actual measured output. The new model named, the minimum distortion power polynomial model (MDP-PM), has been applied in [4] to analog predistorter (PD) design based on a zero-forcing scheme. Better performance over conventional PDs [2,3] was shown in the paper. In the present paper, we will apply the MDP-PM model to another PD design approach, and compare the performance of the resulted PD with conventional PDs and the PD proposed in [4].