Research On Class F Power Amplifiers Applied To Wireless Power Transfer System

Wireless power transmission refers to the transfer of energy from a power source to a load wirelessly.Compared to wired power transmission,wireless power transfer offers several advantages such as environmental friendliness,convenience,and flexibility.The efficiency of the power amplifier plays a crucial role in determining the efficiency of the wireless power transmission transmitter.Improving efficiency is essential for reducing power consumption and thermal design costs at the wireless power transmission transmitter.Among various types of power amplifiers,the Class F amplifier is more suitable for wireless power transmission systems compared to linear and switching power amplifiers.Therefore,this thesis focuses on the study of high-efficiency Class F RF power amplifiers for wireless power transmission systems.The specific contents include:Firstly,the fundamental theory of RF power amplifiers is discussed.Several key performance metrics for power amplifiers are introduced,followed by a detailed description of three major types of RF power amplifiers: linear power amplifiers,switching power amplifiers,and harmonic-tuned power amplifiers.Based on this,a detailed introduction is provided for the Class F RF power amplifier with third harmonic components,which will be designed in this study.Secondly,a Class F RF power amplifier operating at a frequency of 2.45 GHz is designed.The circuit design and optimization simulation of the power amplifier are carried out using ADS.A novel harmonic control circuit structure for the Class F amplifier is proposed.The results of the physical testing after debugging show that when the Class F amplifier operates at an input power of 18 d Bm at 2.45 GHz,it achieves a maximum power-added efficiency of 76.65%,an output power of 38.13 d Bm,and a gain of 20.13 d B.Next,a compact structure Class F RF power amplifier is designed.The miniaturization approach involves using distributed-parameter circuits for the third harmonic impedance control circuit while employing lumped-parameter circuits for the second harmonic impedance control circuit and the remaining circuit.The schematic simulation results indicate that when the designed small-sized Class F amplifier operates at an input power of 24.857 d Bm at 2.45 GHz,it achieves a maximum power-added efficiency of 77.393%,an output power of 38.817 d Bm,and a gain of 13.96 d B.The PCB area of the small-sized Class F amplifier is 33.5mm*12mm,resolving the challenge of simultaneously achieving miniaturization and high efficiency in existing Class F RF power amplifiers.Finally,a time sequence protection circuit is designed to ensure the safe power-up sequence of the power amplifier,where the gate is powered before the drain,protecting the transistor from unsafe power-up conditions.