Selective Intermodulation Compensation in a Multi-Stage Digital Predistorter for Nonlinear Multi-Band Power Amplifiers

This paper presents a technique for suppressing the intermodulation distortion caused by nonlinear multi-band power amplifiers with minimal modeling complexity. The technique is based on generating a narrowband static predistorter for the power amplifier. Then, the intended multi-band signals are resampled and shifted into their representative carrier frequencies before applying the static predistorter in order to accommodate the intermodulation distortion products produced by the nonlinearity. Since the resampling frequency may be high, a study is presented, using filtering techniques to represent low-bandwidth transmitter schemes, to show the accuracy of the intermodulation distortion suppression. Results are presented for the proposed predistorter for two amplifiers: one in a tri-band carrier aggregated LTE scenario in the sub 3 GHz frequencies and another in the millimeter-wave band, demonstrating the effectiveness of reducing the intermodulation products using 5G signals.