Digital predistortion for concurrent multi-band PAs with inter-band IMD compensation

This work attempts to suppress all unfilterable nonlinear distortions in concurrent multi-band power amplifiers (PAs). An even (evenly spaced) mode multi-band model is first derived and then generalized to address intermodulation (IMD) and cross-band modulation products located at the vicinity of the bands of interest. Then, based on only one feedback path, a direct learning method is proposed to compensate these nonlinear distortions. The efficacy of this proposed method is showcased by experimental results on a broadband class-AB GaN PA driven concurrently with 3 long term evolution (LTE) signals located at LTE band 1/2/3. Up to 18dB spectrum emissions suppression was achieved over 400MHz frequency range.