Design and Optimization of a High-Efficiency Current-Biased Reverse Load Modulated Power Amplifier with Impedance and Performance Constraints

We propose an optimization method based on evolutionary computation for the design of broadband high-efficiency current-biased reverse load-modulation power amplifiers (CB-RLM PAs). First, given the reverse load-modulation characteristics of CB-RLM PAs, a comprehensive objective function is proposed that combines multi-state impedance trajectory constraints with in-band performance deviations. For the saturation and 6 dB power back-off (PBO) states, approximately optimal impedance regions on the Smith chart are derived using impedance constraint circles based on load-pull simulations. These regions are used together with in-band performance deviations (e.g., saturated efficiency, 6 dB PBO efficiency, and saturated output power) for matching network optimization and design. Second, a multi-objective evolutionary algorithm based on decomposition with adaptive weights, neighborhood, and global replacement is integrated with harmonic balance simulations to optimize design parameters and evaluate performance. Finally, to validate the proposed method, a broadband CB-RLM PA operating from 0.6 to 1.8 GHz is designed and fabricated. Measurement results show that the efficiencies at saturation, 6 dB PBO, and 8 dB PBO all exceed 43.6%, with saturated output power being maintained at 40.9-41.5 dBm, which confirms the feasibility and effectiveness of the proposed broadband high-efficiency CB-RLM PA optimization and design approach.