| 摘要 |
<p>A method, a differential detector and modulator are disclosed used in FM or PM receivers for demodulating a modulated carrier signal. The detector uses a mixer/phase detector (17) for combining an intermediate frequency phase modulated or frequency modulated signal with the same signal delayed to demodulate the IF signal. Delay is inherent in an IF filter (14) of the receiver in which the detector (17) is utilized for this purpose. The undelayed and delayed signals required for operation of the differential detector (17) are obtained from the input and output respectively of the IF filter (14). The output from the detector (17) has spurious signals not typically present in the output of prior art differential detectors but these spurious signals are removed by a filter (19) including low pass band reject and or notch filtering to yield only the modulating signal. The detector is compact and comparatively unexpensive and can operate at frequencies between 2 MHz and 50 MHz which were heretofore inpractical. </p> |
