The Study On Self-adaptive Locked Technique Of Oven Controlled Crystal Oscillator

A study on technology of lock OCXO (Oven Controlled Crystal Oscillator) based on GPS signals is given in this paper. it combines short-term stability of frequency standards with GPS timing signal's long-term stability and accuracy, which can increase the performance of frequency source greatly, so it has extensive applications in many fields.In this design, in order to eliminate the false pulse signal, the 1PPS (One Pulse Per Second) from GPS receiver must be processed first. Then the phase difference between 1PPS and OCXO is measured in high-resolution time measurement system, the method used here combines the time-amplitude converter with direct counting method, which can effectively eliminate the effect of±1 error. And a Kalman filter is used to process the measurement data in order to eliminate the effects of the phase jitter contained in the 1PPS from GPS. Last, the crystal oscillator is corrected by using a PID controller and proper signal processing circuits. Besides, the GPS signal can become invalid because of various factors, this paper explores the technique which uses history data to correct the frequency errors of frequency standards and maintain its lock precision.This paper accomplishes the ptototype design of locking system based on the theories above, and presents the hardware and software of the system. The results from analyzing experimental data show that the long-term precision and stability are improved to some extent by using this technique. It provides an effective guarantee for our frequency source with low-cost and high-precision.