Compact Broadband Filtering Power Amplifier Using Hybrid Interdigital Capacitor and Microstrip Line Combine Structure

ABSTRACT This paper presents a broadband, highly efficient filtering power amplifier (FPA) operating from 1.6 to 2.6 GHz, realized using a Hybrid Interdigital Capacitor and Microstrip Line Combined Structure, and integrating multifunctional performance within a 78 × 62 mm 2 footprint. In order to co‐design impedance matching and bandpass filtering, the design uses a hybrid output matching network (OMN) with interdigital capacitors and microstrip lines. High selectivity out‐of‐band rejection and compact impedance transformation are provided by the interdigital capacitors while the microstrip lines enable broadband fundamental‐frequency tuning and harmonic absorption. When using a CGH40010F GaN transistor, the FPA achieves a steady gain of 8.5–11.5 dB throughout the whole band, an output power of 38.5–41.5 dBm, and a measured drain efficiency (DE) of 53.5%–72.4%. With input return loss (S11) below 8.1 dB, the hybrid OMN shows > 19.2 dB lower stopband and > 23.1 dB upper‐stopband rejection. This work provides a high‐efficiency solution for wideband wireless systems that need strict spectrum confinement and reduced board space by combining structural compactness and multifunctional integration.