| 摘要 |
<p>APPARATUS FOR RECEIVING AN AM STEREOPHONIC SIGNAL Apparatus for receiving an AM stereophonic signal of the type having monaural information represented by amplitude modulations of a signal carrier and stereophonic information represented by phase modulations of the signal carrier. A reference signal generator generates a reference signal that is synchronized with the signal carrier of the received AM stereophonic signal. In one embodiment, the reference signal generator is a phase-locked loop which generates a reference carrier whose frequency is substantially equal to the signal carrier frequency and whose phase is locked to a predetermined signal carrier phase. An amplitude limiter limits the AM stereophonic signal to remove amplitude modulations of the signal carrier and thereby produce an amplitude-limited signal carrier. A demodulator demodulates the information represented by the AM stereophonic signal, and a detector is provided to detect if the stereophonic information will be properly modulated. A switching arrangement is controlled by the detector to supply the reference signal to the demodulator, whereby the stereophonic information is demodulated, or to supply the amplitude-limited signal carrier to the demodulator, whereby the monaural information is demodulated.</p> |
