Abstract: As a main aspect to measure the performance of the frequency standards, the frequency stability plays an important role in evaluating the stability and reliability of the products. It usually takes a long time to compute the traditional Allan variance for measuring the long-term stability of the frequency standards. In this paper, Total variance, Thêo1 and ThêoH are studied, which can reduce the measuring time in time domain stability analysis comparing with the traditional Allan variance; then, based on the time error data of a Rubidium (Rb) clock measured in the laboratory, these variances are compared and analyzed.

Key words: Time and frequency, Time domain stability, Allan variance, Total variance, ThêoH