应用PID思想的高动态GPS载波跟踪环路设计

摘要

传统的GPS载波跟踪环路对载体的高速运动敏感,难以适应动态环境下基带处理的要求,因此提出一种应用PID思想,融合频率误差微分控制项的环路优化设计方案.分析了载波跟踪环路锁相环的基本结构,将环路中对本地数控振荡器的控制近似为PI模型;根据锁相环的相位输出结果,提取频率误差量,作为增加的微分控制项的输入;适当选取模型参数,构建应用PID控制的GPS载波跟踪环路.仿真结果初步表明,改进方案的环路达到稳态时间比原始方案缩短了10 ms以上,在动态适应性方面显著优于传统跟踪环路.%Traditional GPS carrier tracking loop in GPS receiver is sensitive to high-speed motion of the vehicle, which is difficult to meet the requirements of baseband processing in dynamic environment. So an improved tracking loop scheme is put forward which applies proportion, integration and differentiation (PID)control to fuse differential control items of frequency errors. The basic structure of the carrier tracking phase locked loop (PLL) is analyzed, and the control on the local numerically controlled oscillator (NCO) is approximated to be PI model. According to the phase output of PLL, the magnitude of fiequency error is extracted and taken as the input of the added differential control items. The model parameters are appropriately selected to construct the GPS carrier tracking loop utilizing PID. The simulation results indicate that the improved scheme could reduce the settling time by more than I0 ms, which is more suitable to work in high dynamic environment than traditional tracking loop.