A new prediction method based on the nonlinear autoregressive model is proposed to improve the accuracy of medium-term and long-term predictions of Satellite Clock Bias(SCB).Forecast experiments for three time periods...A new prediction method based on the nonlinear autoregressive model is proposed to improve the accuracy of medium-term and long-term predictions of Satellite Clock Bias(SCB).Forecast experiments for three time periods were implemented based on the precision SCB published on the International GNSS Server(IGS)server.The results show that the medium-term and long-term prediction accuracy of the proposed approach is significantly better compared to other traditional models,with the training time being much shorter than the wavelet neural network model.展开更多
【目的】基于精密单点定位(Precise Point Positioning,PPP)的时间传递技术因其高精度、广覆盖而成为GNSS时间传递中的优势性方法。然而,实践过程中发现接收机码偏差天内短时变化是影响接收机钟差估值精准度的主要偏差之一。【方法】因...【目的】基于精密单点定位(Precise Point Positioning,PPP)的时间传递技术因其高精度、广覆盖而成为GNSS时间传递中的优势性方法。然而,实践过程中发现接收机码偏差天内短时变化是影响接收机钟差估值精准度的主要偏差之一。【方法】因此,本文提出了一种改进的非组合精密单点定位(Modified Precise Point Positioning,MPPP)模型,将接收机码偏差作为时变参数估计,并基于模拟与实测数据进行了方法验证。【结果】结果表明:同等条件下,MPPP授时精度可达0.1~1ns,相较于PPP精度提升30%以上,【结论】可有效克服接收机码偏差变化对实时授时的影响。展开更多
基金2022 Basic Scientific Research Project supported by Liaoning Provincial Education Department(No.LJKMZ20221686)。
文摘A new prediction method based on the nonlinear autoregressive model is proposed to improve the accuracy of medium-term and long-term predictions of Satellite Clock Bias(SCB).Forecast experiments for three time periods were implemented based on the precision SCB published on the International GNSS Server(IGS)server.The results show that the medium-term and long-term prediction accuracy of the proposed approach is significantly better compared to other traditional models,with the training time being much shorter than the wavelet neural network model.
文摘【目的】基于精密单点定位(Precise Point Positioning,PPP)的时间传递技术因其高精度、广覆盖而成为GNSS时间传递中的优势性方法。然而,实践过程中发现接收机码偏差天内短时变化是影响接收机钟差估值精准度的主要偏差之一。【方法】因此,本文提出了一种改进的非组合精密单点定位(Modified Precise Point Positioning,MPPP)模型,将接收机码偏差作为时变参数估计,并基于模拟与实测数据进行了方法验证。【结果】结果表明:同等条件下,MPPP授时精度可达0.1~1ns,相较于PPP精度提升30%以上,【结论】可有效克服接收机码偏差变化对实时授时的影响。
文摘设计了一种嵌入于FPGA芯片的锁相环,实现了四相位时钟、倍频、半整数可编程分频、可调节相位输出功能,满足对于FPGA芯片时钟管理的要求.锁相环采用了自偏置结构,拓展了锁相环的工作范围,缩短了锁定时间,其阻尼系数以及环路带宽和工作频率的比值都仅由电容的比值决定,有效地减小了工艺、电压、温度等对电路的影响.锁相环采用0.18μm CMOS数字工艺,嵌入复旦大学自主研发的FPGA芯片FDP-Ⅱ,经过流片验证,实现了工作频率范围10~600 MHz,整体电路功耗仅为29 mW,锁定时间小于4μs,峰峰值抖动小于±145 ps.
