A miniaturized microstrip suppressing cell as an integrated HCC in class F/F−1 power amplifiers for 5G applications

This study presents the design and implementation of a miniaturized suppressing cell (MSC) functioning as a low-pass filter (LPF) utilizing an interdigital shaped resonator. The MSC is engineered to effectively control harmonics in power amplifiers (PAs), particularly in applications for next-generation 5G systems. The LPF achieves a cut-off frequency of 2.21 GHz, demonstrating a sharp transition region spanning 0.6 GHz, where the attenuation transitions from −3 to −40 dB. Notably, the filter exhibits an ultra-extended rejection bandwidth, maintaining at least −20 dB from 2.8 to 29.17 GHz. The measured flat group delay further confirms the excellent passband performance of this LPF, indicating minimal signal distortion. Given the critical role of harmonic control circuits (HCCs) in enhancing the efficiency and linearity of various PA classes, including class-F and class-F⁻¹ configuration, the proposed MSC serves as a vital component in HCC designs. This advancement not only contributes to improved performance in PAs but also supports the demands of modern wireless communication systems, reinforcing the MSC's significance in high-frequency applications.