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报道一种新型 X波段 0 .2 5 μm PHEMT全单片集成低噪声子系统。该子系统由开关衰减电路、采样检波电路和低噪声放大器三部分组成。开关插入损耗仅 0 .5 d B,放大器噪声系数小于 1 .5 d B。当开关控制电压为-2 V,输入电平 <-7d Bm时 ,此系统相当于一个低噪声放大器。在 8.5～ 1 0 .5 GHz频率内 ,整个系统增益大于2 4d B,噪声系数小于 2 .0 d B,输入输出 VSWR<1 .5 ;但当输入电平 >-7d Bm时 ,采样检波电路开始工作 ,打开主放大器前的开关衰减器 ,限制输入功率进入 LNA。输入功率越大 ,反射越大。在开关控制电压为 +2 V时 ,无论输入功率多大 ,开关关闭通道
A new X-band 0.52 μm PHEMT fully monolithic integrated low-noise subsystem is reported. The subsystem consists of switch attenuation circuit, sampling detector circuit and low noise amplifier. The switch insertion loss is only 0.5 dB and the amplifier noise figure is less than 1.5 dB. When the switching control voltage is -2 V and the input level is <-7 dBm, this system is equivalent to a low-noise amplifier. At 8.5 ~ 1.05 GHz, the gain of the whole system is more than 2 4d B, the noise figure is less than 2.0d B, the input and output VSWR <1.5; but when the input level> -7d Bm, the detector circuit Start working, turn on the switch attenuator in front of the main amplifier, limit the input power into the LNA. The greater the input power, the greater the reflection. When the switch control voltage is +2 V, the switch closes the channel, no matter how much input power