电磁法仪器高精度GPS同步系统设计

摘要

To improve the synchronization precision and anti-interference of electromagnetic instruments, a new scheme of synchronization system was proposed based on Global Positioning System and oven controlled crystal oscillator (OCXO) clock. By analyzing the GPS second pulse characteristics and OCXO frequency characteristics, Kalman filter was adopted to eliminate the random noise in second pulse. In order to guarantee the accuracy of OCXO frequency, on-line PID control method was used to correct the OCXO. The reference signal of the controller is the filtered second pulse. MC9S12XS128 was used in the control unit to realize Kalman filter algorithm and OCXO PID correction. The results show that synchronization precision is stable within 25 ns when the GPS is locked. The proposed scheme improves the precision and anti-interference of the synchronization system. The efficiency of the instruments can be enhanced.%为了提高电磁法勘探仪器同步系统的同步精度和抗干扰性，提出一种新的基于全球定位系统(GPS)和恒温晶振(OCXO)的同步系统方案。通过对GPS秒脉冲特性和OCXO频率特性的分析，采用卡尔曼滤波对秒脉冲中的随机噪声进行滤波处理，提高其精度。并以处理后的秒脉冲信号作为基准在线校正OCXO基本时钟，保证其输出频率的精度。采用具有电磁兼容设计的MC9S12XS128微控制器实现秒脉冲的卡尔曼滤波和OCXO在线PID校正，提高系统的抗干扰能力。研究结果表明：GPS锁定时同步脉冲精度稳定在25 ns以内。该方案提高同步系统的同步精度和抗干扰性，同时可以提高仪器野外工作的效率。