| 摘要 |
PURPOSE:To prevent abnormal synchronization with simple configuration by sampling an eye pattern of demodulation data at a speed twice the transmission speed so as to discriminate the normal synchronization and the abnormal synchronization. CONSTITUTION:A demodulation base band signal is identified by an identification device 4 to generate a phase error signal by a phase error signal generating circuit 12, it is used as a control signal to drive an oscillation means 9 and to generate (10) a reconditioned carrier. A phase difference of 90 deg. is given to the reconditioned carrier and the result is mixed with a reception signal by mixers 2a, 2b to obtain a demodulated base band signal. In this case, out of synchronism of the carrier is monitored (11) based on the demodulated base band signal, a demodulated eye pattern of the demodulated reception data by a means 13 is sampled at a speed twice the transmission speed of the reception data, and an error in the data is detected from a detection area of the sampled data to detect the abnormal synchronization. When the abnormal synchronization is detected, the means 13 generates a signal for a prescribed time under the condition of the absence of carrier out of synchronism, a selection means 7 selects a reference signal as a control signal in response to the signal from the means 13 and sends the signal to an oscillation means 9. |
