Dynamic Activation Digital Predistortion of RF Power Amplifiers for 6G Dynamic Spectrum Aggregation Applications

In this article, a novel dynamic activation digital predistortion (DPD) technique is proposed to linearize radio frequency (RF) power amplifiers (PAs) for 6G dynamic spectrum aggregation (DSA) applications. It is achieved by developing a low-complexity single model to deal with multiple operating modes and dynamic configurations. By leveraging nonlinear prior knowledge and incorporating the dynamic configurations of each frequency band into the dual-band (DB) neural network (NN) model, a novel DPD model specifically designed for linearizing PAs operating in dynamic DB mode is proposed. To make the model compatible with single-band (SB) mode, a dynamic activation method is proposed, which can dynamically activate the model architecture based on the current operating mode. With this operation, PAs in both SB and DB modes can be efficiently linearized using a single DPD model with appropriate complexity. Experiment tests are conducted on GaN Doherty PAs in sub-6-GHz and millimeter-wave frequencies, which involve varying operating modes (SB and DB) and dynamic configurations (input power, operating frequency, and signal bandwidth). The test results demonstrate that the proposed technique achieves comparable DPD performance using a single model in contrast to conventional DPD methods that would require multiple models, which highlights the effectiveness of the proposed DPD method.