| 摘要 |
The proposed radiometer with zero indication contains a symmetrical circulator, attenuator, two signal mixers, a modulating signal generator, a heterodyne, a noise signal generator, an intermediate-frequency signal amplifier, a demodulator, two synchronous detectors, two low-pass filters, an analog-to-digital converter, a displaying unit, and a switching unit. The input of the circulator is connected to the output of the antenna of the radiometer, and the first output is connected to the corresponding input of the switching unit. The output of the first synchronous detector is connected to the displaying unit via the first low-pass filter. The output of the noise signal generator is connected to the corresponding input of the switching unit via the attenuator. The second output of the circulator is connected to the input of the second mixer. The output of the second mixer is connected to the inputs of the intermediate-frequency signal amplifier, demodulator, second synchronous detector, and second filter. The output of the second filter is connected to the corresponding input of the analog-to-digital converter. The output of the converter is connected to the control inputs of the modulating signal generator and synchronous detectors. The output of the heterodyne is connected to the corresponding input of the first mixer.
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