Synthesis of Broadband Differential Loading Networks for High-Efficiency Power Amplifiers

A synthesis procedure of broadband loading networks for high-efficiency power amplifiers is presented. The design method utilizes the transfer function parameters from a periodic N-section network and the required impedance at the intrinsic transistor drain that produces high efficiency. The selected network topology is differential band-pass and allows the combining of two FETs to produce high power with lower device parasitics compared to a single-ended equivalent. This paper describes the synthesis procedure with a prototype design to achieve an output power of 100-W with a drain efficiency higher than 77% within the 240–380 MHz frequency range.