| 摘要 |
PURPOSE:To prevent mis-detection of a carrier wave due to noise component, by using a narrow band pass filter filtering only one side band frequency components of upper or lower side bands of the carrier wave subjected to a polyphase PSK modulation so as to improve the C/N. CONSTITUTION:The narrow band filter 4 filters only either one side band frequency component of the upper and the lower side bands of a carrier wave subjected to the polyphase PSK modulation such as 0, pi modulation or the like from an input signal fed to a detecting circuit. An envelope detector 2 detects the envelope of an output signal of a filter 4. A voltage comparator 3 compares an envelope output voltage of the envelope detector 2 with a prescribed threshold voltage and when the output voltage exceeds the threshold value, a detecting signal is transmitted to the carrier. |
