| 摘要 |
PURPOSE:To adjust the frequency of a window signal with a good accuracy by a simple circuit constitution without destroying the duty ratio of the window signal divided by 50% by providing a digital VFO consisting of a counter, a comparator, a signal generator and so on. CONSTITUTION:In the digital VFO, a comparator 3-12 compares an input value with an inversed result to have inverted the output bit of a counter 3-13, and a signal generator 3-15 generates and outputs a control signal corresponding to this compared result. And based on this control signal, the operation of the counter 3-13 is controlled. In this case, as the control signal, for example, two kinds of signals are outputted, one is the signal for reducing the cycle of the window signal, and the other is the signal for increasing the cycle of the window signal. Here, these signals are distributed properly in the one cycle of the window signal, and the duty ratio of the window signal is approximate to the 50%. Therefore, without destroying the duty ratio of the window signal divided by 50%, it is possible to adjust the frequency of the window signal by the simple circuit constitution with the good accuracy. |
