CIRCUIT FOR DETECTING DIGITAL SYNCHRONOUS SIGNAL

摘要

PURPOSE:To change the error permissible value of a pattern comparing part in accordance with an S/N by preparing plural pattern data having different error allowable bits and selecting the pattern data by the output of an automatic gain control voltage detecting circuit. CONSTITUTION:A digital intermediate frequency signal applied to an input terminal 11 is inputted to a demodulator 12 and an AGC voltage detecting circuit 15. The output of the demodulator 12 is applied to the shift register 13 of R bits, where it is converted into parallel data and is inputted to a pattern comparing part 14. It has a ROM of RX(L+1) bits, and prepares previously plural pattern data for permitting errors with respect to the address input of R bits. Any one of them is selected by a switch 16 in accordance with the output of the AGC voltage detecting circuit 15, and the error permissible bit is decided.