| 摘要 |
IN TV RECEIVING APPARATUS, A FIRST IF AMPLIFIER CHAIN COMPRISES A FIRST GAIN-CONTROLLED AMPLIFIER FOLLOWED IN CASCADE CONNECTION BY A SECOND GAIN-CONTROLLED AMPLIFIER, AND A SECOND IF AMPLIFIER CHAIN COMPRISES A THIRD GAIN-CONTROLLED AMPLIFIER FOLLOWED IN CASCADE CONNECTION BY A FOURTH GAIN-CONTROLLED AMPLIFIER. THE SECOND AND FOURTH GAIN-CONTROLLED AMPLIFIERS ARE CONTROLLED SIMILARLY BY AN AGC SIGNAL, AND THE FIRST AND THIRD GAIN-CONTROLLED AMPLIFIERS ARE CONTROLLED SIMILARLY BY THAT AGC SIGNAL DELAYED IN SIMILAR AMOUNTS. AN RF AMPLIFIER (12) IS GAIN-CONTROLLED RESPONSIVE TO THAT AGC SIGNAL DELAYED EVEN MORE, AND MORE, AND A DOWNCONVERTER (14) SUPPLIES FIRST DETECTOR RESPONSE TO AMPLIFIED RF, WHICH FIRST DETECTOR RESPONSE IS APPLIED TO THE-FIRST AND SECOND IF AMPLIFIER CHAINS BY RESPECTIVE FREQUENCY-SELECTIVE FILTERS. THE IF AMPLIFIER RESPONSE IS DOWNCONVERTED TO GENERATE SOUND IF. THE IF AMPLIFIER RESPONSE IS DETECTED TO RECOVER VIDEO SIGNAL. AN AGC DETECTOR (56) DETECTS THE PEAKS OF THE SYNCHRONIZING PULSES INCLUDED IN THE VIDEO SIGNAL TO DEVELOP THE AGC SIGNAL. (FIG.9)
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