| 摘要 |
PURPOSE:To detect an accurate CN ratio signal Scn even in the case that the level of a received digital modulation signal is low. CONSTITUTION:The CN ratio detecting circuit which detects the CN ratio of the received digital modulation signal includes a band-pass filter 2 connected to a clock component extracting circuit 1 in a demodulator 4 and a detecting circuit 3 which detects the output signal of the filter 2. The clock component extracting circuit 1 extracts only the clock signal component used to prescribe data at the time of modulation, namely, the shift signal component which has a frequency or a phase shifted in every clock period. The band-pass filter 2 has the band pass characteristic having the clock frequency as the center frequency. |
