應用於極寬頻之射頻高功率放大器設計與實現

Abstract

射頻功率放大器是通訊系統中的關鍵元件,而寬頻的射頻功率放大器更有高於一般的設計難度,且通常為系統中最昂貴的硬體,除了在通訊系統外,雷達與高階醫療儀器中亦常見寬頻的射頻功率放大器的使用. 本論文揭櫫一種適用於VHF 延伸至部份L 波段的極寬頻射頻高功率放大器設計方法,採用擁有高功率密度的氮化鎵電晶體作為功率元件,利用非線性模型進行模擬設計,並用FR4 電路板實現驗證與調測,設計的挑戰在於需同時間兼顧頻寬與輸出功率,量測結果顯示頻寬可由150 MHz 延伸至1200 MHz,飽和功率可達5 瓦,效率超過40%.

Many wireless communication transceivers, radars and medical instruments involve RF power amplifier. To design a narrow band RF power amplifier is difficult, but to design a broad band RF power amplifier is even more challenged. This thesis introduces a method to design an extremely broad band RF power amplifier frequency ranging from VHF through UHF to lower L band. A GaN HEMT is used to construct this power amplifier because of the intrinsic broad band and high power characteristic. To achieve such low Q in the pass band, a low pass type Bridged-T input matching network is adopted. Resistive feedback between the gate and the drain is used to enhance the gain flatness. The output matching network is implemented with LC sections optimized for broad band performance. The measurement data shows bandwidth ranging from 150 MHz to 1200 MHz, 5 W saturation output power, and PAE over 40%.