APD–SSPP: Enhancing Linearization of Power Amplifier Using Spoof Surface Plasmon Polariton Propagation

ABSTRACT This paper presents a compact analog predistortion (APD) employing spoof surface plasmon polaritons (SSPPs) to enhance the linearization of high‐frequency radio frequency (RF) power amplifiers (PAs). The APD–SSPP architecture integrates a Schottky diode (DBES105a) with a high‐Q tank circuit to improve harmonic suppression and mitigate third‐order intermodulation distortions (IMD3). The SSPP‐enabled impedance transformation enhances electromagnetic wave confinement, suppresses parasitic resonance effects, and optimizes power transfer efficiency by minimizing impedance mismatches along the signal path. Furthermore, broadband harmonic rejection is achieved by integrating radial stub elements, effectively mitigating spectral regrowth while maintaining high‐power‐added efficiency. Applied to the PA (ZX60‐V63), the proposed APD–SSPP achieves a gain tuning range of 3 dB, a phase variation of 0.9°, and an insertion loss of 4 dB. Experimental validation confirms that by using APD–SSPP, 65.9% IMD3 suppression, 14.5% carrier‐to‐intermodulation improvement, and a 36% adjacent channel power ratio reduction are achieved, significantly reducing out‐of‐band spectral emissions and improving the linearization performance of ZX60‐V63. These results establish the APD–SSPP as a highly efficient, miniaturized predistortion solution for next‐generation RF front‐end architectures in high‐data‐rate wireless communication systems.