Highly-accurate real-time syntonization by use of a single-frequency receiver with GPS carrier phase

The purpose of this paper is to develop a low-cost, highly-accurate and real-time syntonization system composed of a single-frequency receiver with GPS carrier phase. For averaging time of one day under the configuration, our experimental results showed that the accuracy of the steered clock could be improved from about two parts in 10⁹ to about three parts in 10¹⁴ , and the stability of the syntonized clock could be improved from about nine parts in 10¹⁰ to about four parts in 10¹⁴ . Three improvements and advantages in our methodology were given. First, we developed a forecasting model with recurrent neural networks to correct atmospheric errors in real time. The model was more accurate than the existed ionosphere model and troposphere model for a single-frequency receiver. Furthermore, it was available simply and anticipative day-to-day partially, irrelevant to user locations. Second, the low-cost clock could be automatically steered to obtain the very high frequency accuracy and stability in the short term as well as in the long term. Experimental results showed the stability of per second was about nine parts in 10¹². Compared with the commercial GPS disciplined oscillator (GPSDO), the short term stability (1s) was improved about ten times. Third, the frequency performance of the syntonization system by use of low-cost GPS engines, inexpensive clocks and less communication effects was as good as the commercial atomic clock. So, the frame of syntonization was sound, reliable and cost-effective.