| 摘要 |
An AGC circuit comprising a first level wave-detecting circuit for wave-detecting received signals having been band-limited, having a sensitivity being particularly high for a central frequency of a desired channel and a sensitivity being low for the other frequencies, and a second level wave-detecting circuit for wave-detecting received signals before the band-limitation having a sensitivity being constant irrespective of the frequency. Since the wave-detected signals of these two wave-detecting circuits are mutually added, it is possible to set an optimum detecting sensitivity by the first level wave-detecting signal against adjacent disturbances close to the central frequency of the desired channel, thereby effectively suppressing disturbance signals taking place when the respective intensities of the electric fields of adjacent channels are similar. Also, it is possible to set a constant detecting sensitivity by the second level wave-detecting signal against an intermodulation disturbance having a detuning degree over a predetermined value, thereby preventing an excessive sensitivity suppression of the frequency of the desired channel caused by an excessive AGC application.
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