| 摘要 |
PURPOSE:To uniform the duty factor of an output pulse width by extracting selectively a pulse wave having the mean period of two input FM waves when synthesizing and recording or transmitting two FM waves which vary independently. CONSTITUTION:A pulse width detecting circuit 15 generates an output pulse when the ''1''-level or ''0''-level width of a pulse signal at an output terminal 14 is reduced to less than some set value (TMIN). For example, when the ''1''-level pulse width is reduced to less than the set value TMIN, a signal W outputted so far is switched to a next signal X or -X, but when a decision on a ''1''-level pulse is made, the inverted output, i.e. signal -X is selected subsequently. Thus, the rising and falling points of one of both input signals and those of the other signal are detected by two frequency and phase comparators 9 and 10 respectively; when one output pulse has extremely narrow or wide width, the signal is switched to the other signal to make uniform the duty factor of the output pulse width. |
