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<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>) high power amplifiers (HPAs) at S, C and Ku-bands using commercial off-the-shelf (COTS) ICs and commercial Nonlinear Embedding (NLE) models. By relying on COTS components, the need for fabricating custom and expensive 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 load-pull-based fundamental source and load matching, is proposed to overcome their individual limitations. The proposed approach achieves optimum RF power and 3% higher Power- Added Efficiency (PAE) in S-band (81% vs 78%), 4.5% higher PAE in C-band (78% vs 72.5%) & more than 5% higher PAE in Ku-band (64% vs 57%), compared to prior COTS and MMIC-based works. A continuous-wave (CW) Class-F PA at 2 GHz is developed first as a baseline, and the design methodology is then extended to 5.5 GHz and 11.2 GHz (where transistor parasitics necessitate an inverse-Class-F topology). Dielectric constant variations beyond 10 GHz are analyzed, and a novel Class-F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> harmonic control network (HCN) is introduced to achieve a first-pass design at 11.2 GHz. The fabricated prototypes include a 10 W Class-F HPA at 2 GHz, a 10 W inverse-Class-F HPA at 5.5 GHz and a miniaturized 25 W Class-F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> HPA at 11.2 GHz. Performance measurements of these HPAs confirm superior efficiency, optimum RF output power and efficient thermal management (using 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.