Apparatus for determining when a preselected phase relationship exists between two periodic waveforms

摘要

Apparatus for determining when two periodic signals are within preselected limits of being in phase, includes square wave generators which convert the periodic signals to pulse trains, and an AND gate which combines the pulse trains to generate a rectangular wave signal having a logic one value when the two pulse trains overlap. A monostable one-shot multivibrator generates clock pulses in response to the leading edge of the rectangular wave signal. A flip-flop latches its output to the logic level of the rectangular wave signal on the trailing edge of the clock pulses. The clock pulses are of a duration representative of the selected phase angle limit, so that the output of the flip-flop is a phase angle acceptance window having a logic 1 value when the difference in phase between the periodic signals is within the selected limits.