Linearization of Microwave Emitters using an Adaptive Digital Predistorter

Adaptive digital predistortion for nonlinear power amplifier (PA) became one of the most robust linearization techniques that can be implemented in digital signal processors (DSP) environment. However, its precision compensation for AM-AM and AM-PM distortion is wasted when the quadrature modulator (QM) impairments are not to be considered. This paper presents a new digital predistorter for microwave emitters with real time modeling of both, PA and QM distortions, that can compensate for nonlinearity, gain imbalance, phase imbalance and DC offset. An improvement of 35 dB of out-of-band power is obtained in simulating with 105 complex input look-up table using 2D interpolation.