| 摘要 |
PURPOSE:To detect a level of a carrier signal of a channel different from a busy channel by providing specific 1st and 2nd frequency converter circuits to the system without provision of two series of transmission and reception sections. CONSTITUTION:A reception input signal is not divided into two but fed to a band pass filter(BPF) 13 and to a mixer 15, in which the signal is frequency- mixed with a local signal with a fixed frequency from a fixed frequency oscillator 41, then the received high frequency signal is frequency-converted into a central frequency signal while being multiplexed on the frequency axis. Furthermore, I, Q channel detection outputs are converted respectively into digital signals at A/D converters 26,27 and frequency-converted by frequency conversion circuits 43,44, signals corresponding to two objective channels included in the input high frequency signal are outputted as signals whose center frequency is zero, and they are fed respectively to a demodulation circuit 28 and a level detection circuit 45. Thus, one of the two signals is demodulated and the level of the other is detected, or both signals are demodulated in this way. |
