Network Synthesis, Transforms and Practical Issues for Broadband High Efficiency Power Amplifiers
High-efficiency power amplifiers require specific impedances at the fundamental frequency as well as the harmonics at the active device intrinsic drain (FETs) or collector (HBTs). Therefore, it is necessary to design a loading network that is able to present optimum impedances to achieve a specific performance. Design equations for loading-network synthesis will be presented for different amplifier classes and design examples will be given. Often, the resultant network presents practical difficulties, i.e.; impractical component values; sensitivity to PWB parasitic and requires extra components for impedance matching to 50-Ohms. Using network transforms the aforementioned practical issues can be overcame. Also, loading networks can be synthesized and transform to a require topology in order to present the required impedances over a wide frequency range and therefore broadband performance and high-efficiency.