现代卫星通讯利用非恒包络数字调制技术,需要高效宽带线性功率放大器.由于行波管高效率和宽带特性广泛应用于卫星通讯中,但是其强非线性造成带外失真和带内干扰影响通讯质量.模拟预失真由于其电路简单易于实现、低功耗、小体积、高可靠性等优点适用于卫星通讯.该文介绍一种宽带行波管线性化器设计,扩展带宽达到1.2 GHz,频率范围19.8~21.0 GHz.测试结果显示该线性化器在带宽1.2 GHz内,非线性可以在幅度扩张2~5 dB,相位扩张20~50°内调整,双音测试时,输入双音信号功率回退6 dB时与行波管级联测试后三阶交调改善17.8 dB,取得很好的改善效果.%The modern satellite communication uses non-constant envelope digital modulation techniques and thus demands for the high efficiency, wideband linear high-power amplifiers. The travelling wave tube (TWT) amplifier is widely used in digital wireless communication systems because of its high power efficiency and broadband, but its strong nonlinear characteristic generates intermodulation distortion, which degrades the data quality of transmitted signal and causes interference in adjacent channels. The current techniques such as baseband prediction and feedforward technique cannot achieve wideband greater than 1 GHz, and they are too complex to be used on satellite. This paper presents a broadband predistortion TWT linearizer. A frequency bandwidth of 1.2 GHz has been demonstrated with a K-band TWTA between 19.8 GHz and 21.0 GHz. The measurement result shows that the linearizer delivers about 2 dB to 5 dB of gain expansion and 20-50 degrees phase shift expansion. And the cascaded LTWTA shows good nonlinearity improvement of 17.8 dB at 6 dB input power back off point.
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