基于新校频算法的GPS可驯铷钟系统研究

Study on GPS Disciplined Rb Clock Based on New Frequency Accuracy Measurement Algorithm

在 GPS可驯铷钟系统中 ,校频是驯频的前提。常用高精度校频算法的不足在于需要昂贵的高分辨时间间隔计数器。提出了一种新的校频算法。使用最小分辨率为 0 .1μs的低分辨时间间隔计数卡 ,测量铷钟和 GPS定时接收机二者秒信号的时差 ,然后设计了卡尔曼滤波算法 ,并在单片机中实现 ,对时差数据进行平滑 ,克服由于 GPS的秒信号、铷钟的秒信号的不稳定和测量噪声带来的影响 ,估计出高精度的时差数据 ,从而在较短时间内获得很高的校频精度。该方法将 GPS作为频率基准 ,间接得到了铷钟相对于与 GPS的频差 ,避免了使用昂贵的高分辨计数器。使用该校频算法 ,对 PRS10铷钟进行驯频 ,研制了可驯铷钟系统。对系统的测量结果表明 :在不影响铷钟短期稳定度的情况下 ,频率准确度一般优于 5× 10 - 1 2 。

Frequency accuracy measurement is the basis of frequency disciplined in GPS disciplined Rb clock system. The disadvantage of high precision frequency accuracy measurement method available is that an expensive high-resolution time interval counter is needed. A new frequency accuracy measurement method is presented. A counter card with the resolution of 0.1 microsecond is chosen to measure the time interval between the lpps of Rb atom clock and that of GPS time receiver. After that, a Kalman filtering algorithm is developed on single chip computer with smooth of the time difference data, to restrain the influence of instability of the lpps signal of Rb clock and GPS time receiver and measurement noise. The accurate time difference is then estimated and frequency accuracy is calculated with high precision in short period. In the method, GPS is looked on as reference and the frequency difference between the Rb clock and GPS may be obtained indirectly, and the expensive high-resolution counter may not be needed. Based on the new frequency accuracy measurement algorithm, PRS10 disciplined Rb system is developed. Measurement data show that the frequency accuracy is better than 5 × 10-12 in the condition that the short-term stability of PRS10 is not influenced.