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为了解决在全球卫星定位系统(GPS)接收机中出现的阶梯状伪距测量结果的问题,在分析了接收机中伪码跟踪原理的基础上,找到了造成该问题的原因。通过研究数控振荡器(NCO)中相位舍位噪声的规律,得到了该噪声与数字中频采样率的关系,提出了基于减小相位舍位噪声的中频采样率优化方案。仿真结果显示:选择高于且接近伪码速率整数倍的中频采样率能明显的抑止NCO相位舍位噪声。优选出的高分辨率、低漂移的数字中频采样率可以有效提高GPS接收机的跟踪精度。
In order to solve the problem of staircase pseudorange measurements in GPS receivers, the cause of this problem was found after analyzing the principle of pseudo-code tracking in the receiver. The relationship between the noise and the digital intermediate frequency sampling rate is obtained by studying the law of the phase truncation noise in the NCO, and the intermediate frequency sampling rate optimization scheme based on the phase truncation noise reduction is proposed. Simulation results show that the selection of intermediate frequency sampling rate higher than and close to the integer multiple of the pseudo-code rate can significantly suppress the NCO phase truncation noise. The optimized high-resolution, low-drift digital IF sampling rate can effectively improve the GPS receiver tracking accuracy.