| 摘要 |
PURPOSE: An AGC system operating based on a desired signal is provided to operate a tuner AGC and an IF AGC based on a desired signal so as to minimize an error in signal magnitudes. CONSTITUTION: An AGC system operating based on a desired signal includes a tuner(210), the first and second filters(220,240), an intermediate frequency amplifier(250), a demodulator(270), and a level detector(260). The tuner converts the frequency of an input signal into a specific intermediate frequency and controls the magnitude of a signal according to a DC component inputted. The first filter passes only a specific band of the IF frequency signal. The intermediate frequency amplifier amplifies the output signal of the first filter according to a level extracted by the level detector. The demodulator demodulates the signal amplified by the intermediate frequency amplifier. The second filter extracts the DC component from the output signal of the demodulator to feedback the DC component to the tuner. The level detector detects a predetermined DC level from the output signal of the filter to control the signal gain of the intermediate frequency amplifier.
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