High-Efficiency Transmission-Line GaN HEMT Inverse Class F Power Amplifier for Active Antenna Arrays

In this paper, a novel load-network solution to implement the transmission-line inverse Class F power amplifier for WCDMA active antenna array applications is presented. The theoretical analysis is based on an analytical derivation of the optimum load-network parameters to control the second and third harmonic at the device output including the device output parasitic shunt capacitance and series inductance. For an inverse Class F power amplifier based on a Nitronex GaN HEMT NPTB00004 with hybrid microstrip implementation, the simulated output power of 37 dBm and power-added efficiency of more than 70% are achieved at a supply voltage of 25 V in a frequency bandwidth of 2.11 to 2.17 GHz. The test board with implemented inverse Class F GaN HEMT power amplifier has been measured and high-performance results with drain efficiencies of about 80% and higher were achieved across the wide ranges of bias supply voltages and operating frequencies. Index Terms -- RF power amplifier, inverse Class F, transmission line, efficiency, circuit design, resonant circuit, transistor.