| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a data transmitter that can surely detect a null period even when a high level noise is intruded to data and stably detect synchronization even in the case of a transmission channel under a bad condition. SOLUTION: In the data transmitter adopting a digital modulation system and recovering synchronization at a receiver side on the basis of a prescribed synchronous symbol group inserted to a transmission signal, a receiver side is provided with a filter circuit that eliminates an out-band noise of a received signal, the power of the received signal from which the out-band noise is eliminated is obtained, a threshold is calculated on the basis of the mean power for a prescribed period of the received signal powers, using the received signal power and the threshold detects and decides a silence signal period of the synchronous symbol group and the synchronization is recovered at the receiver side on the basis of the discrimination result.</p> |
