Digital Predistortion for Concurrent Dual-band Millimeter Wave Analog Multibeam Transmitters

This brief proposes a novel digital predistortion (DPD) technique to linearize concurrent dual-band millimeter wave (mmWave) analog multibeam transmitters. Beams at the same frequency band give full play to the spatial multiplexing, so as to improve spectrum utilization. By means of detailed analysis of the system characteristics, a DPD model is proposed to effectively eliminate the distortions caused by power amplifiers (PAs) including nonlinearity, memory effect, the intermodulation distortion (IMD) between two different frequency bands, and the multibeam interference incurred in undesirable sidelobes in the main beam direction simultaneously. To validate the proposed idea, a test bench of mmWave analog multibeam transmitter utilizing Butler matrix was designed, and then it was stimulated by a concurrent dual-band signal at 26.91 GHz and 27.09 GHz, respectively. Compared with existing DPD techniques, the proposed method is suitable for compensating the distortions in dual-band analog multibeam transmitters, which has shown its great potential for the applications in future mmWave concurrent dual-band multibeam wireless communication systems.