| 摘要 |
PURPOSE:To attain synchronization of a demodulated signal quickly by estimating the recovery of a reception state based on the correlation between a reception signal and a fixed word in a timing when the fixed word is to be received when the reception signal is momentarily interrupted and no fixed word is detected. CONSTITUTION:A synchronization detector 1 multiplies a carrier recovered by a carrier recovery device 2 with an input signal R to obtain a demodulation signal D. A frame synchronizing circuit 3 detects a fixed word inserted periodically to a transmission signal from the signal D to take frame synchronization. When the signal is momentarily interrupted, no fixed word is detected and frame synchronization is not taken. The circuit 3 fixes the frequency of the recovered carrier to the recovery device 2 and outputs an aperture signal to a correlation device 4, in which the correlation is obtained by a prescribed calculation. Then a signal detector 7 compares an output of a power detector 6 with a prescribed threshold level and activates a Fourier transformation device 9 when the output exceeds the threshold level, the device 9 detects a frequency error and eliminates it and the signal D well-synchronized is obtained. |
