In this paper, a broadband class-F-1 power amplifier (PA) that can be integrated into compact-sized micro-radio units is introduced. This PA utilizes a multi-harmonic impedance merging technique at harmonic frequencies so that the circuit areas of matching networks can be minimized. As well, in order to maximize the bandwidth of high efficiency, circuit configuration was optimized by the first order differentiation of the fundamental-frequency impedance. For the sake of verification, a 10 W inverse class-F PA operating at 1.9 GHz was designed with a commercial GaN transistor. It exhibited a 39.2% size reduction as compared to conventional PAs of the similar power. In addition, it exhibited a bandwidth of 600 MHz (1.6 ~ 2.2 GHz) at an efficiency greater than 60%, a peak efficiency of 83.9%, and an output power of 42.2 dBm.
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