| 摘要 |
PURPOSE: A low noise frequency converter is provided to selectively receive one of two polarized signals without using a switching circuit to frequency-convert the received polarized signal and output the signal without deteriorating characteristic of the signal. CONSTITUTION: A low noise frequency converter includes a feed horn(21) having the first probe(21a) of receiving left hand circular polarization and the second probe(21b) of receiving right hand circular polarization, the first and second low noise amplifiers(22,23) for low-noise-amplifying satellite signals received through the first and second probes, respectively, the first and second band pass filters(24,25) for band-pass-filtering the satellite signals output from the first and second low noise amplifiers, the first mixer(26) for mixing the satellite signal from the band pass filter with the first local oscillating signal to convert the signal into the first intermediate frequency signal, and the second mixer(27) for mixing the satellite signal output from the second band pass filter with the second local oscillating signal to convert the satellite signal into the second intermediate frequency signal. The low noise frequency converter further includes the first and second low pass filters(30,31) for removing signals other than the first and second intermediate frequency signals from the output signals of the first and second mixers, the first and second intermediate frequency amplifiers(32,33) for amplifying the first and second intermediate frequency signals, and the third low pass filter(34) for removing signals higher than the first intermediate frequency signal from the output signal of the first intermediate frequency amplifier. The frequency converter also has a high pass filter(35) for removing signals lower than the second intermediate frequency from the output signal of the second intermediate frequency amplifier, and a spurious attenuator(36) for attenuating a spurious signal of the output signals of the third low pass filter and the high pass filter.
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