| 摘要 |
PURPOSE:To surely detect the synchronization of an electromagnetic wave whose phase is modulated and to improve the reliability of communications by transmitting a sine wave with a fixed frequency to a receiver from a transmitter prior to data transmission and acquiring the synchronization of a data transmission wave based on the frequency of the received sine wave. CONSTITUTION:Prior to data transmission, the sine wave with a fixed frequency is transmitted to the underground receiver 20 from the transmitter 90 in a pit. Receiving the wave, the receiver 20 acquries the synchronization of the data transmission wave based on the frequency of the received sine wave. Namely, the underground transmitter 90 first transmits the sine wave with a fixed frequency. The receiver 20, receiving that, stores information about the frequency. Then the transmitter 90 receives the data transmission wave. When receiving that, the receiver 20 detects the synchronization of the data transmission wave with the aid of the frequency of the having been received sine wave. Thus a reference for detection waves becomes precise. Therefore the detection is made more precisely, and the reliability of reception data is improved. |
