| 摘要 |
PURPOSE:To convert the output of a counter circuit into a carrier reproduction signal by comparing the frequency output of a counter circuit of a division ratio variable control type with a frequency corresponding to the carrier of a descending data signal and varying the division ratio of the counter circuit according to the result of said comparison. CONSTITUTION:A carrier reproducing circuit 22 gives two-multiplication to the output of an AGC circuit by a multiplying circuit 30 to obtain an output having a frequency double as much as the carrier frequency of a descending data signal. This output is received by a phase comparator 32 in the form of an input signal S1 through a BPF31 having a pass frequency approximate to a double frequency. The output S2 of the comparator 32 is converted into a DC output S3 by an averaging circuit 33 consisting of an LPF and applied to a level comparator 34. The comparison output S4 is applied to a dividing circuit 35 of a division variable type as a division ratio switching signal. An output pulse S5 of the circuit 35 is fed back to the circuit 32 and also transmitted to a phase wave detecting circuit as a reproduction carrier signal. |
