| 摘要 |
PURPOSE:To obtain a sine wave output which synchronizes with the waveform of an input rectangular wave by providing a differentiating circuit which differentiates the input rectangular wave, variable frequency dividing circuit which delays output pulses of the differentiating circuit as specified, fixed frequency dividing circuit which divides the frequency of a specified clock and outputs a sine wave of reference frequency, and pseudo sine wave generating circuit which generates a staircase sine wave according to the output of the fixed frequency dividing circuit, and filter which extracts its output frequency component. CONSTITUTION:The N-stage pseudo sine wave generating circuit 2 generates the staircase sine wave of one period with N clock inputs. Further, a frequency dividing circuit 10 divides the frequency of a basic clock from an input terminal 5 and outputs a clock of frequency N times as high as frequencies almost in the center of the range of sampled values of the rectangular wave input frequency. The differentiating circuit composed of two D flip-flops 11 and 12 and an OR gate 13 detects the leading edge of the rectangular wave [figure (a)] inputted from a terminal 6 and outputs a pulse [figure (b)]. A counter 14 counts up clock inputs in response to said output pulse up to a constant set number of basic clocks, but this circuit corresponds to the variable frequency dividing circuit which delays differential pulses. |
