Design of a High-Efficiency Class-AB RF Power Amplifier for 3.7–4.2 GHz Band

Power amplifiers are important in today's wireless communication systems. This paper describes the design, tuning, and performance optimization of a class-AB power amplifier operating in the 3.7 GHz – 4.2 GHz frequency range with an output power of 40 dBm at a gain of about 10 dB. A Wolfspeed CGH40010F GaN HEMT transistor, which operates from DC with a 28V supply, is employed in the amplifier's design to satisfy the specifications. Using the transistor nonlinear simulation model created by Cree Inc., an amplifier is designed and simulated in Keysight Advanced Design System (ADS) software. Keeping the issues of linearity and efficiency in mind, the biasing point is chosen for the class AB configuration. In biasing, the drain current is 48 mA and the gate-source voltage is −3.05 V. The frequency range for the design is chosen based on applications. Then, the stability analysis of the transistor is performed. The simulation results also show that the transistor becomes broadband stable when a resistor is added to its input side. Source-pull and load-pull simulation is used to extract source and load impedances for optimal power and efficiency. From the perspectives of efficiency and linearity, the installed PA performs exceptionally well across the entire frequency range. According to the simulation, the RF PA's flat gain fluctuated between 8.19 dB and 10.90 dB for the frequency range of 3.7 GHz to 4.2 GHz. At 3.8 GHz, the maximum power added efficiency (PAE) was found to be 64.52%, while the maximum drain efficiency is simulated to reach 67.78% at an output power of nearly 40 dBm.