Phase group characteristic based frequency measurement method with wide band and fast response

As the rapid development of frequency standard, the need arises to measure frequency fast in a wide band with a high resolution. The frequency measurement instrument in commerce nowadays cannot meet the demand. And the generally existing +1 counting error limits the improvement of measuring precision. By analyzing the phase variation rule between every two periodic signals with different frequency, the phase group characteristics, such as phase group synchronization, are revealed in the paper. Based on the phase group characteristics and phase coincidence detection, a wide band frequency measurement method is proposed in this paper. Two adjacent phase coincidence points of the reference frequency and the measured frequency are used to generate the measurement gate, and ±1 counting error can be eliminated effectively. Fine phase shift is used in some special situation on the reference frequency to shorten the measurement time. Experiment results show that this method achieves a precision higher than 1 × 10^-13/s in frequency standard comparison, and the typical precision of signal from 30 kHz to 100MHz achieve 6~8 × 10^-12/s.