Research And Realization Of Technology Locked Second-Class Frequency Standards By GPS Signal

A study on technology of lock second-class frequency standards based on GPS signals is given in this paper. Frequency standards such as crystal oscillator and rubidium atomic clock are calibrated by GPS pulses-per-second signal in this technology, which can combine short-term stability of frequency standards with GPS timing signal's long-term stability and accuracy. Thus frequency source with high accuracy and low-cost can be obtained.A method of high precision to measure time interval is presented in this paper. This method combines time-amplitude converter with direct counting method to measure the phase difference between 1PPS and local frequency standard's signal. The resolution of the method is 120ps and its measurement range is up to second-class, which can effectively eliminate the effect of±1 error. In order to reduce the effect of 1PPS jitter, Kalman filter algorithm is used to process time-interval measurement data. The algorithm can reduce the error introduced by 1PPS jitter to±2ns. In study of the voltage-controlled properties of local frequency standard, PWM signal of controllable duty cycle is generated to realize high-precision D/A converter combined with integral circuit. Thus frequency of lock second-class frequency standard is calibrated.This paper accomplishes the design and achievement of the ptototype of locking system. System structure, the design of system of hardware and software, system performance test, error analysis and correction methods are given in this paper. Of a crystal oscillator calibrated by this way, better than 1×10^-11/s second-class frequency stability,5×10^-11 frequency accuracy and 3.5×10^-11/day frequency drift are expected.