Long-distance Transmission Of Standard Time Signal To Lock The Local Crystal Oscillator Method

As the all-weather and high precision standard time signal supplied by the satellite positioning systems is widely used, the method proves worthy of research, which obtains a frequency signal with both excellent long-term and short-term stability by locking the local oscillator on the standard time signal that transmitted from a long distance. In this paper, a solution of a control system, which uses the standard time signal as the system reference to lock the local VCXO, is proposed. Paper describes the principle of the PLL, the linearized model of its modules, its hardware and software implementation. A high precision time to digital converter (TDC), which increases the phase detector precision to 0.5ns, is introduced. Moreover, by combining dual 12-bit D/A converters and high-precision low-noise operational amplifiers, a novel method with the advantage of low cost, is brought in to improve the precision and the dynamic range of the actuator. In addition, all the relative digital circuit and its software are given in the paper. Arithmetic of the filtering signal extrapolating and the closed-loop control are studied. To overcome the high noise of the reference frequency and meet output system requirement of the high control precision, two filtering and control arithmetic, which hold the short-term stability of the VCXO and improve its long-term stability by the reference, are described in detail. At the end of the paper, the experiment data, which achieve 1.5×10-11 precision and generally reach the level of the same type products both here and abroad, are provided.