Phase difference variation characteristics between frequency signals and its uses in measurement

On the basis of phase difference variation characteristics between frequency signals, regularities of periodic signals can be recognized essentially. This paper describes the characteristics with which the greatest common factor frequency, the least common multiple period and quantized minimum variation of phase difference vary according to the frequency relationship between two signals. It analyses the influence of `phase coincidences´ distribution between signals upon the measurement. According to the characteristics, using the phase coincidence detection method highly accurate measurements of frequency and other periodic signal parameters can be accomplished. A much higher accuracy can be obtained for some special frequency signals. By means of the principle, a lot of new instruments have been built. They show more than 3 to 5 orders accuracy over that of ordinary instruments