Adaptive matching for efficiency enhancement of GAN class-F power amplifiers

In this work a 6 W GaN based class-F amplifier is presented. The presented amplifier uses an adaptive matching output network to achieve high efficiency over 8.5 dB output dynamic range. The output matching network is an L matching network with a tunable inductor and a tunable capacitor. The tunable inductor is based on a ⋋/4 impedance inverter and a switchable capacitor bank. The tunable inductor presents a short circuit for the second harmonic and an open circuit to the third harmonic; additionally together with the tunable capacitor they present the optimum working impedance for the transistor. The designed amplifier has a power added efficiency of 72.0 % at an output power of 38 dBm and through using adaptive matching it can achieve a PAE of 58% at an output power of 29.5 dBm, in contrast to a PAE of only 26% in the case of using a fixed matching network.