| 摘要 |
PROBLEM TO BE SOLVED: To provide a system of selectively using a plurality (two or over) of channel frequencies for suppressing the effects of the distortion of a steady- state unwanted wave on a main wave. SOLUTION: A broadband BPF 1, whose pass band is a frequency band of a plurality (two or more) of channels included in an RF input signal, is provided with a pre-stage of an RF-AFC amplifier 2. This automatic gain control system is provided with a BPF, whose pass band is a frequency band of a main wave and a BPF, whose eliminating band is the frequency band of the main wave and that is connected in parallel with this BPF. Output signals of the BPF and BEF are detected and compared to control a gain of the RF- AGC amplifier 2, so that it outputs a signal of a prescribed level, even when an input electric field strength is being increased.
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