| 摘要 |
The method and apparatus for providing an AM stereo receiver suitable for receiving an AM/PM modulated RF carrier frequency, the receiver uses a standard AM detector to receive said AM/PM modulated intermediate frequency and to provide an 1+r signal. The stereo detector system further provides an 1-r signal and comprises means (104) for receiving and limiting the amplitude of the AM/PM modulated signal to eliminate the amplitude modulation therefrom and for providing a signal having phase modulation only. The limited AM/PM signal from limiter (104) is then provided to an FM quadrature detector (106) for recovering any PM signal. The PM signal detected and provided by said FM quadrature detector (106) is then integrated by an integrator (124) to provide a true PM signal. The output of integrator (124) is provided to a squelch gate (128) and to a means for sampling and determining the presence of a 5 Hz signal. The means for sampling and determining comprises a 5 hz band pass filter (130), a squaring circuit (132) and a missing pulse detector (134). The squelch gate (128) receives a control signal from missing pulse detector (134) along with the 1-r signal from integrator (124). The 1-r signal then passes through squelch gate (128) in response to the presence of the control signal which indicates a stereo broadcast. The output from squelch gate (128) which is the 1-r signal is then combined with the 1+r signal from the standard AM detector by a matrix (102) to provide a true L and a true R signal for a stereo AM broadcast.
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