| 摘要 |
PURPOSE:To eliminate the need for a carrier wave with high accuracy for a receiver by inserting a pilot signal to a transmission signal and utilizing the pilot signal to match its frequency to a transmission frequency in a voltage controlled oscillator of a receiver. CONSTITUTION:A sound signal inputted to a terminal and the pilot signal are transmitted from an antenna via a synthesis circuit and a signal received by the antenna 11 is inputted to an amplifier circuit 13 via a receiving circuit 12. An output of the circuit 13 is subjected to AGC control by a band pass filter 16, a comparator circuit 17, and a reference voltage generating circuit 18. The output of the circuit 13 is inputted to an amplitude detecting circuit 21 and an amplitude limit circuit 22, and an output of the circuit 22 is inputted to a gain control amplifier circuit 26 via a frequency detecting circuit 23, a volage controlled oscillating circuit 24, and a pilot signal elimination band stop filter 25. Further, the circuit 26 is controlled by a comparator circuit 31 and a band pass filter 29 or the like extracting the pilot signal so that an output frequency of the circuit 24 is made equal to a pilot frequency signal oscillated from an oscillating circuit 30. |
