Digital phase detector

A digital system for measuring a phase relationship between two noisy signals of a given period wherein the phase difference measurement may lie in the range of from 0 to 360 degrees. The noisy signals are amplified and limited so that the processed signal only contains noise in the time vicinity around the zero crossing points. Time interval counters are utilized to measure the time delay between signals and the time period of the reference signal. Phase relationship may be determined by multiplying the ratio of the two digital numbers produced by 360 DEG . Errors in digital outputs are minimized by digitally integrating the counter input during the noisy zero crossover periods. The measurements are completed within two period times of the signals being measured and may be repeated in each of the succeeding two period times.