High-Efficiency Transmitters Operating at HF, VHF, and UHF Frequencies

A comprehensive review and comparative analysis of modern high-efficiency RF transmitter architectures operating in the HF, VHF, and UHF frequency bands is presented. These bands remain crucial for applications such as broadcasting, navigation, civil and military communications, land mobile radio and both satellite and land-based aeronautical communications. The paper focuses on prominent architectures such as Doherty Power Amplifiers (DPA), Envelope Elimination and Restoration (EER), and Outphasing Amplifiers (OPA), detailing their operating principles, key advantages, and implementation challenges. For each architecture, experimental hardware prototypes are described to illustrate real-world performance in representative scenarios across the HF, VHF, and UHF bands. The article concludes by analyzing the inherent trade-offs between efficiency, linearity, and implementation complexity, and discusses the prospects of hybrid and multiband approaches of emerging transmitter systems.