| 摘要 |
PROBLEM TO BE SOLVED: To provide the FSK demodulation circuit immune to the effect of noise. SOLUTION: In the case of demodulating biphase data from a wobble signal subject to FSK modulation by the biphase data whose 3.5 periods are used for one bit, an edge detection circuit generates an edge pulse signal for each half period. In this case, counters 205, 206 and an AND circuit 207 or the like are used to mask an edge pulse signal including a pulse produced by noise and generates an edge pulse signal for about a half period of the wobble signal. Moreover, pulse signals (edge 0-5) for 3 periods each are generated from an edge pulse signal while deviating them by a half period each. Thus, the quantity (high/low) of the frequency of the wobble signal is discriminated by using them to detect a time width of the period of the wobble signal so as to demodulate the by the biphase data. |
