X頻帶平衡式功率放大器使用新奇分歧耦合器

Abstract

本篇論文提出一供可移動衛星發射器使用之平衡式功率放大器,利用一 種改良型微帶線阻抗轉換分歧耦合器取代傳統耦合器;因為此種耦合器有 直流隔絕的功能,可以容易地對兩級主動電路作串接,因此可節省隔絕電容 成本及減少電路面積,使更適合MMIC化. 此一X頻帶功率放大器分為三級, 第一級是以高移動電晶體製作,第二級與第三級以砷化鎵場效電晶體製作. 為了達到高效率,單一級功率放大器採用Class AB類偏壓並完成設計P1dB 為22dBm之功率放大器.為了高功率及高效率的要求.我們將兩個單一級放 大器整合成一平衡式功率放大器.此一平衡式放大器P1dB為25dBm,相對應 最大效率為50%,增益為9dB.在沒有加諧波抑制器下,第二次諧波抑制可 達40dBc. In this report, we present an X-band balanced power amplifier using a novel microstrip line" DC Blocking Impedance- Transforming Branch-line Coupler(DCITBC)"for mobile satellite communication. Because this novel coupler has the function of dc blocking, which can easily cascade two stage of active circuit together, we can cut down the cost and reduce the circuit size. Therefore, it is suitable for MMIC applications. The X-band power amplifier has three stages. The first stage is a HEMT and the second and the third stages are GaAs MESFET amplifiers. The single-ended power amplifier operated at Class AB for high power-added efficiency with about saturation power 22dBm. In order to obtain high power and high efficiency, we designed balanced amplifier using novel DCITBC. The overall circuit of balanced power amplifier has acheived 9dB gain, 26dBm output power, and near 50% power-added efficiency over the 9.8-10.2GHzband. In addition, the level of second harmonic is less than -40dBc without extra harmonic rejetor.