A New Technique for the Characterization and Design of Class-F RF Power Amplifiers

In class-F RF power amplifiers, there are several methodologies used to characterize the RF power device in order to present the proper harmonic impedances at its terminals, the most widely used of which is the load-pull method. This paper presents an alternative technique based on the analytic derivation of the optimum terminal load impedances at the first three harmonic frequencies using both the device intrinsic and package parasitic elements. The output matching network is then synthesized analytically to present the calculated harmonic impedances at the device output terminal. As a confirmation to the proposed technique, a 6-W power amplifier circuit has been designed and simulated using a commercial GaN HEMT power device to operate at 900 MHz. The simulated results show a drain efficiency of more than 84%, output power of more than 38 dBm, and power gain of more than 13 dB at the specified frequency.