This talk is an overview of techniques for high-efficiency RF power amplification. First, some basic concepts about transistors and the concept of average efficiency are introduced. The characteristics of conventional amplifiers (classes A, B, and C) are then reviewed. The principles, demonstrated achievements, and practical limitations of RF-power amplifiers operating in class D, class E, and class F are then discussed. The talk concludes with a discussion of techniques for linear amplification using high-level amplitude modulation via a class-S modulator and the Kahn envelope-elimination and restoration technique.
The Kahn envelope-elimination and restoration (EER) technique allows efficient but nonlinear RF amplifiers to be used to implement a high-efficiency linear transmitter. Fundamentally, a narrowband RF signal is regarded as simultaneous amplitude and phase modulation. The phase-modulated carrier is amplified efficiently by a chain of nonlinear RF amplifiers and the envelope is restored by high-level amplitude modulation of the final amplifier. This talk reviews the concept of average efficiency and then reviews the principles and requirements for the EER technique.
Low-Cost High-Efficiency HF Power Amplifiers
Recently marketed "low-cost" RF-power MOSFETs in plastic TO-247 packages are capable of generating significant RF power at high efficiency in single-frequency RF applications. This paper explores the use of these MOSFETs in broadband power amplifiers. PAs operating in classes D, DE, and E are compared.