摘要
为解决GPS易受外界环境影响,同步授时易失锁这一问题,设计出一种基于FPGA的保证GPS与OCXO协同工作的高精度同步授时解决方案.采用在FPGA内部构造延迟线的方法来对时间间隔进行测量,使时间测量精度可达到71ps和10ps,从而确保了时间间隔测量的高准确性.以GPS提供的秒脉冲1PPS作为标准信号对OCXO的频率进行校准,再在FPGA中采用均值滤波算法对1PPS信号引入的随机噪声进行压制,实际验证表明,该设计具有很好的频率校准效果.FPGA每完成一次校准就对同步修正一次,保证了GPS在任何时候失锁时,本地秒脉冲都与1PPS具有很高的初始同步精度.当完成频率校准后,GPS分别失锁150min,6h,12h,24h,同步精度仍可达到410ns,1.6us,2us和33us.这优于V5-2000的同步精度.长期实测表明,该方案可以很好地结合GPS授时和OCXO授时的优点,解决了GPS同步授时存在的问题.这不仅满足所有电法勘探的分布式采集系统对同步授时的精度要求,而且适用其它需要高精度同步授时的工业领域.该方案的设计只在一片FPGA中完成,这最大限度地减少了外围器件的消耗和外围电路的复杂程度,降低了功耗.
The GPS（Global Position System）timing is vulnerable to the external environment which makes the synchronous timing become lock-lose easily.Based on FPGA（Field Programmable Gate Array）.The paper aims to design a high-proximity synchronous timing plan to make GPS and OCXO（Oven Controlled Crystal Oscillator） work synergistically.The application of building a delay line inside FPGA to measure the interval time makes the timing precision reach to 71 ps and 10 ps,ensuring the high accuracy of it.The average filtering algorithm is employed to suppress the random noise brought by 1PPS（Pulses per Second）which is used as a standard signal to correct the frequency of the OCXO,which is demonstrated to be very effective.The synchronous timing is amended simultaneously with the calibration of FPGA,which guarantees high initial precision between LPS（Local Pulses per Second）and 1PPS whenever the GPS becomes lock-lose.After frequency correction is completed,the synchronous precision reaches 410 ns,1.6us,2us and 33 us,with the GPS losing lock 150 min,6h,12 h,and 24 hrespectively,which is more accurate than V5-2000.Long-term measurement demonstrates that the plan can combine the advantages of GPS timing and OCXO timing,thus to solve the problem existed in the GPS timing.It not only meets the precision requirements of synchronous timing in all the distributed acquisition systems for electrical prospecting,but also can be applied in other industrial fields with high precision requirements.The plan goes on in one FPGA chip,which greatly reduces the consumption of peripheral elements and simplifies the complexity of the peripheral circuit,thus reduced the cost and power.
出处
《地球物理学进展》
CSCD
北大核心
2015年第4期1870-1881,共12页
Progress in Geophysics
基金
中央高校基本科研业务费专项资金(2014zzts255)资助
关键词
GPS授时
OCXO
校频
同步
FPGA
电法勘探
GPS timing
OCXO
frequency calibration
synchronization
FPGA
electrical prospecting
