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现代雷达中输入信号幅度的动态范围一般为80—100分贝。雷达信号处理所用设备的动态范围大大低于此值,因此常出现过载现象。为了使输入信号幅度的动态范围和接收设备的动态范围相匹配,通常要用调整增益的办法来压缩被处理信号的动态范围。调整接收机各个输入级的增益必然使其参数变坏。下面介绍的低噪声参量衰减器可用来压缩输入信号幅度的动态范围而接收机的参数不会显著变坏。图1所示为参量衰减器的框图。参量衰减器包括参量设备(参量二极管;信号滤波器;泵频滤波器和组合频率滤波器)和自适应通道(窄带前置放大器;变频器和泵频放大器)。
The dynamic range of the input signal amplitude in modern radars is typically 80-100 dB. The dynamic range of the equipment used for radar signal processing is significantly below this value, so overload often occurs. In order to match the dynamic range of the input signal amplitude to the dynamic range of the receiving device, the gain of the gain is usually used to compress the dynamic range of the signal being processed. Adjusting the gain of each input stage of the receiver inevitably makes its parameters worse. The low noise parametric attenuator described below can be used to compress the dynamic range of the input signal amplitude without significant deterioration of the receiver parameters. Figure 1 shows a block diagram of the parametric attenuator. Parametric attenuators include parametric devices (parametric diodes; signal filters; pump filters and combined frequency filters) and adaptive channels (narrowband preamplifiers; frequency converters and pump amplifiers).