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本文介绍已用于卫星通信地面接收小站,取代常温参放作为前置低噪声放大器的4GHz低噪声AaAsFET放大器的研制情况。文中分析FET放大器的噪声模型;阐明FET放大器的噪声与频率及温度的关系;提供放大器电路的设计与调整方法;最后给出由两级FET组成的放大器的实测性能:增益G>20dB,平坦带宽B>500MHz,整机噪声温度Ter≤150K(含输入波导隔离转换及接收机后级的影响),增益波动△G<±0.5dB,增益斜率△G/△f≤±0.2d B/50MHz,群时延τ_(P-P)≤0.4ns/任意50MHz,1dB增益压缩点的输出功率P_(out)=+4dBm,三次交调产物与载波比I/G≤55dB,工作环境温度t=-40℃～+50℃。
This article describes the development of a 4GHz low-noise AaAsFET amplifier that has been used in satellite communications ground receiving stations to replace ambient-temperature preamps as a front-end low-noise amplifier. In this paper, the noise model of FET amplifier is analyzed. The relationship between the noise of FET amplifier and frequency and temperature is clarified. The design and adjustment method of amplifier circuit is provided. Finally, the measured performance of the amplifier consisting of two FETs is obtained: gain G> 20dB, B> 500MHz, the overall noise temperature Ter≤150K (including the input waveguide isolation conversion and the receiver after the level of), the gain fluctuation △ G <± 0.5dB, gain slope △ G / △ f ≤ ± 0.2d B / 50MHz, Group delay τ_ (PP) ≤0.4ns / arbitrary 50MHz, 1dB gain Compression point output power Pout = + 4dBm, the third intermodulation product and carrier ratio I / G≤55dB, the working environment temperature t = -40 ℃ ~ + 50 ℃.