| 摘要 |
PURPOSE:To prevent malfunction due to spurious signal generated in harmonics of a signal current frequency, by providing a demodulator after a BPF selecting a signal current, in a signal reception circuit of a channel converter of an FDM carrier system. CONSTITUTION:A basic group P(60-108kHz) inputted to an input terminal 1 is demodulated at a demodulator 2 with a carrier C and signal current BPF6 selects 131.85kHz. This signal current is demodulated into 3.85kHz with a carrier 128kHz, and amplified 13 and rectified 9 to drive a relay 10. The signal frequency f0= 131.85kHz of the output of the BPF6 and unnecessary wave by spurious 2f0= 263.7kHz are obtained and the unnecessary wave demodulated with the carrier C=128kHz is 135.7, 259.85 and 391.7kHz, then malfunction in the unnecessary wave signal in this frequency can be prevented. |
