Investigation and Design of Ultra-Wideband Resistive-Reactive Series of Continuous Inverse Modes Power Amplifier With Input Second-Harmonic Manipulation

In this article, the analysis of a series of continuous inverse modes power amplifiers (PAs) with resistive-reactive is presented under the impact of input nonlinearity. Theoretical analysis manifests that, different from the conventional extended series of inverse continuous modes (ESCIMs), where the source second harmonic is short-circuited, the second harmonic generated by input nonlinearity can promote and maintain the performance of PAs over a wide frequency band within a flexible impedance range. Furthermore, in the presence of input nonlinearity, a new load design space is reshaped and combined with the source second-harmonic manipulation space generated by input nonlinearity to collaboratively achieve optimal ESCIMs PAs performance. Subsequently, based on the proposed design theory, an ultra-wideband PA is designed, implemented, and fabricated using a two-stage cascaded square ring stub-loaded resonator microstrip bandpass filter architecture with wideband response and a commercially available 10-W gallium nitride (GaN) device. The measurement results show that in the frequency band range of 0.4-4.0 GHz with a relative bandwidth of 160%, a drain efficiency of 55.3-73.8%, an output power of 38.9-41.9 dBm, and a gain of 8.9-11.9 dB have been achieved under saturated output power. Measurement results confirm the theoretical findings reported in this paper.