Hybrid Load-Pull and Nonlinear Embedding Approach for High-Efficiency GaN Class-F/F⁻¹ Power Amplifier Design in Satellite Applications

This work presents the design and development of GaN-based high-efficiency Class-F and Inverse-Class-F (Class-F−1) High Power Amplifiers (HPAs) at S, C, and Ku-bands using commercial ICs and Nonlinear Embedding (NLE) models. By relying on commercial off-the-shelf (COTS) components, the need for fabricating proprietary semiconductor dies and limited-access transistor models for Class-F operations is eliminated. A hybrid design methodology, combining NLE-based optimal harmonic terminations with optimum loadpull-based fundamental source and load matching, is proposed to overcome their individual limitations. Compared to prior COTS and MMIC-based studies, the proposed methodology achieves optimum RF power along with 3% higher Power-Added Efficiency (PAE) in S-band (81% vs. 78%), 4.5% higher in C-band (78% vs. 72.5%), and more than 5% higher in Ku-band (64% vs. 57%). A continuous-wave (CW) 2 GHz 10 W Class-F HPA prototype is developed first as a baseline, and the design methodology is then extended to a 10 W Class-F−1 HPA at 5.5 GHz and a miniaturized 25 W Class-F−1 HPA at 11.2 GHz (where transistor parasitics necessitate a Class-F−1 topology). Dielectric constant variations beyond 10 GHz are analyzed, and a novel Class-F−1 Harmonic Control Network (HCN) is introduced to achieve a first-pass design at 11.2 GHz. Performance measurements of these HPAs confirm superior efficiency, optimum RF output power, and efficient thermal management (using a low-cost copper-coin ring). The proposed CW GaN-based amplifiers (with linearizers) offer a compact, efficient, and reliable alternative to bulky and power-hungry traveling-wave tube amplifiers (TWTAs), making them highly suitable for satellite transponders and ground-based systems.