Directed Graph Navigated Digital Predistortion of mmWave Power Amplifiers for 6G Hopping Applications

To exploit the limited communication resources, the real-time carrier frequency of the power amplifier (PA) may hop, which will result in rapid change in PA's nonlinear behavior and bring huge challenge to make the digital predistortion (DPD) response in a timely manner. Different from the conventional methods that attempt to shorten the DPD updating time, a novel scheme of controlling its nonlinear variation is proposed. By analyzing PA's various behaviors using graph model and extracting a directed graph to navigate its power adjustments, the variation in nonlinear behavior induced by hopping carrier frequency can be effectively compensated, which will mitigate the DPD performance deterioration when there is not enough time for DPD update. Finally, the proposed method was validated by experiments on a 100-MHz modulated signal stimulated millimeter-wave (mmWave) PA operating at five hopping carrier frequencies from 26.4 to 28 GHz, with the step of 400 MHz.