| 摘要 |
<p>PURPOSE:To provide the subject detecting circuit which can shorten the time when the digital date has a hit and then a data hit detecting signal is transmitted and also can work stably even with a low C/N ratio. CONSTITUTION:A frame synchronization protecting circuit (a synchronization detector 1, a coincident counter 2, a discordant counter 3 or a frame counter 4, etc.) protects the frame synchronizing signals produced by the frame synchronization patterns which are included in a prescribed cycle in the received digital data. Then a correlative pattern synchronization detector 9 is provided to the frame synchronization protecting circuit to detect the correlative discordance of the frame synchronization patterns and to produce a detection pulse together with a discordance detector 11 which produces a discordance signal based on the inverted signal of the detection pulse and the retrieving position pulse of the frame synchronization pattern obtained by the frame synchronization protecting circuit, and a circuit (a flip-flop 8) which receives the discordance signal and outputs a date hit detection signal.</p> |
