| 摘要 |
PURPOSE:To improve both the signal transmitting reliability and the interference detecting accuracy, by setting two waves outside a main signal band as the carrier waves for transmission of digital signals and using the carrier wave frequency also for detection of interference. CONSTITUTION:At the communication side, the audio signal sent from a terminal 101 is supplied to an adder 104 through an amplitude limiter 102 and a BPF103. While subcarrier generators 106 and 107 receive ON/OFF keying by the digital signal sent from a code generator 105. The keyed signals are added together by an adder 110 through BPF108 and 109 and then synthesized with the analog audio signals at the adder 104. These synthesized signals are transmitted after undergoing FM modulation through a transmitter 111. |
