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RF signal receiver with phase- locked loop demodulator having variable bandwidth means
RF signal receiver with phase- locked loop demodulator having variable bandwidth means
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机译：具有具有可变带宽装置的锁相环解调器的RF信号接收机
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摘要
An FM receiver apparatus includes a frequency tuner and a phase-locked loop demodulator having a loop amplifier filter means for recovering of the modulated signal. The phase-locked loop detector includes a high quality voltage controlled oscillator (9) driving a tuned signal phase comparator (8) connected to a loop filter (10) which includes an active loop amplifier. The output of the filter is connected to drive the voltage control oscillator. The loop filter serves to set the bandwidth of the demodulation in accordance with the amplifier gain, the resistance capacitance filter components and the like. The loop filter includes a fixed capacitance (11) establishing a large signal bandwidth. A second fixed capacitor (21) is connected in series with FET transistor (22) in a series branch connected in parallel with the fixed bandwidth capacitor (11). An RF signal signal amplitude detector (24, 25) actuates the FET transistor to reduce the bandwidth of the phase-locked loop demodulator with the RF signal such that the loop filter pass-band tracks the tuner pass-band characteristic, particularly when a weak signal is received. IMAGE
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