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本文详细地分析了反射型放大器的环行器对放大器噪声特性的影响。放大器本体产生的噪声随环行器一次通路衰减的增减和输入口至输出口的泄漏而变化。由于环行器自身损耗引起的噪声增加,同一次通路衰减中减去反射损耗的部分相当。来自放大器后面的隔离器负载上的噪声,以及从3口向接有放大器本体的2口的泄漏使噪声特性进一步恶化。当放大器接至天线时,来自隔离器的噪声由于天线的剩余反射而被反射,这也使噪声特性恶化。来自天线的这一反射,由于它与由3口向2口的泄漏部分存在着相位关系,故是电压和的关系,引起噪声特性相当大的恶化。使用冷热负载测量噪声温度时,由于这些负载的剩余反射使来自隔离器的噪声被反射,产生测量误差。这种情况下,也是由于这一反射与环行器泄漏之间相位关系,对误差造成很大影响。
This paper analyzes in detail the effect of the circulator on the noise characteristics of the amplifier. The noise generated by the amplifier body varies with the increase / decrease of the primary path attenuation of the circulator and the leakage from the input port to the output port. Due to the increase of the noise caused by the circulator’s own loss, the part of the same path attenuation minus the reflection loss is equivalent. Noise from the load on the isolator behind the amplifier and from the three ports to the two ports connected to the amplifier body further deteriorate the noise characteristics. When the amplifier is connected to the antenna, the noise from the isolator is reflected due to the residual reflection of the antenna, which also deteriorates the noise characteristics. This reflection from the antenna, due to its phase relationship with the leakage from 3 ports to 2 ports, is voltage-dependent and causes a considerable deterioration of the noise characteristics. When using a thermal load to measure the noise temperature, the noise from the isolator is reflected due to the residual reflections of these loads, creating measurement errors. In this case, too, the phase relationship between this reflection and the circulator leakage greatly affects the error.