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It models realistically users motion, and radio signals propagation in a citylike scenario.


The sound (tone signals) propagation is studied on a 510mlong constantdepth (38 m) track (TON310 Hz) and a 10.6kmlong track (TON320 Hz), which is set up by placing the selfcontained transmitter at the bottom (at a depth of 65 m).


Both backplanes have been successfully manufactured and tested, after careful prelayout simulation of the signals propagation and integrity.




 Based on the basic equation used for calculating the time transfer via GPS, the error factors affecting the transfer accuracy are summarized into following three parts: the control unit's capability to monitor GPS clocks and satellite clocks and predict satellite's ephemeris, the influences of the time delay error caused by the mediums in the signal propagation path, which include ionospheric delay correction, tropospheric correction and correction for the rotation of the Earth (Sagnac effect), and the... Based on the basic equation used for calculating the time transfer via GPS, the error factors affecting the transfer accuracy are summarized into following three parts: the control unit's capability to monitor GPS clocks and satellite clocks and predict satellite's ephemeris, the influences of the time delay error caused by the mediums in the signal propagation path, which include ionospheric delay correction, tropospheric correction and correction for the rotation of the Earth (Sagnac effect), and the user's errors, which refer to those caused by the receiver itself and by the environment conditions. These effects on the time transfer accuracy are analyzed and calculated in this paper in order to find out a way to improve it.  从GPS时间传递的基本公式出发,将影响传递精度的因素归纳为3部分:GPS系统本身的监控质量、信号传播路径的延迟和用户系统。系统的监控质量包括GPS系统钟的控制、卫星钟和卫星星历的误差等。信号传播过程中引起的时间延迟对时间传递结果的影响最直接,需进行修正,包括电离层修正、对流层修正和地球自转引起传播路径变化的修正等。用户系统的误差主要指接收机本身引入的测量误差。本文将讨论这3部分误差源,分析、计算这些因素对时间传递精度的影响,从用户的需要探讨提高传递精度的的途径。  The principle and error assessments of the application of spaceborne GPS radio occultation to terrestrial atmosphere inversion are reviewed and the recent developments on this discipline are summarized. Based on the established theory and data from GPS/MET mission, researchers from University Corporation for Atmosphere Research in US have presented their results that the accuracy of GPS occultation inversion for atmospheric temperature is averagely one Kelvin between 5 km and 40 km altitude. If temperature is... The principle and error assessments of the application of spaceborne GPS radio occultation to terrestrial atmosphere inversion are reviewed and the recent developments on this discipline are summarized. Based on the established theory and data from GPS/MET mission, researchers from University Corporation for Atmosphere Research in US have presented their results that the accuracy of GPS occultation inversion for atmospheric temperature is averagely one Kelvin between 5 km and 40 km altitude. If temperature is obtainable from an independent source, water vapour pressure profiles can be derived, which is quite interesting to meteorologists; however it is still tentative to derive water vapor profile because before reliable results for water vapor profiles are attainable, the multipath effect on signal, which is difficult to model, should be mostly removed. Currently, inversion accuracies suffer much from signal to noise ratio limiting, so inflight GPS receivers for obtaining lower signal to noise ratio GPS signal are required in order to get more effective data for inverting atmospheric parameters. As far as the characteristics of the technique in question are concerned, we raise some problems which remain to be settled. They include: how to narrow and interpret the differences of temperature derived by GPS occultation method and routine technique, such as Radiosonde; how to get atmospheric parameters in the lower atmosphere, say, under 5 km altitude, and in the upper atmosphere, say, above 40 km; how to decorrelate temperature and water vapour pressure so as to get reliable water vapour pressure profiles; how to take into account the ignored “higher order” term, which can be expressed as the integral of the dot product between gradient of refractivity and velocity of GPS signal with respect to the geocenter, integrating along the signal propagation path; how to overcome the singularity of integrand at the lower integration limiting when the Abel transform is adopted to produce the refractivity profiles.  给出了空间无线电掩星反演大气参数的原理及其误差估计方法 ,介绍了国内外在该领域的研究进展。并针对该技术的一些特点 ,指出了若干尚需解决的问题。  Multichannel GPS satellite signal simulator provides realistic test signals for GPS receivers and navigation systems. In this paper, signals arriving the antenna of GPS receiver are analyzed from the point of view of simulator design. Focus is put on the estimation methods of several signal parameters that are difficult to determine directly according to existing experiential models due to various error factors. Based on the theory of Artificial Neural Network (ANN), an approach to simulate... Multichannel GPS satellite signal simulator provides realistic test signals for GPS receivers and navigation systems. In this paper, signals arriving the antenna of GPS receiver are analyzed from the point of view of simulator design. Focus is put on the estimation methods of several signal parameters that are difficult to determine directly according to existing experiential models due to various error factors. Based on the theory of Artificial Neural Network (ANN), an approach to simulate signal propagation delay, carrier phase, power, and other parameters using ANN is proposed. The architecture of the hardwareintheloop test system is given. The ANN training and validation process is described. Experimental results demonstrate that the ANN designed can simulate sample data statistically in high fidelity. Therefore the computation of signal state based on this ANN can meet the design requirement, and can be directly applied to the development of multichannel GPS satellite signal simulator.  多通道全球定位系统(GPS)卫星信号模拟器用来为GPS接收机和导航系统提供逼真的测试信号。该文从模拟器设计的角度对到达GPS接收机天线的卫星信号进行了分析,着重讨论了因众多误差因素影响而不易直接利用经验模型确定的几个波形参量的估计问题。基于人工神经网络(ANN)理论,提出一种利用ANN来模拟信号传播延迟、载波相位、信号功率等参量的方法。给出了基于ANN的模拟器闭环测试系统的结构。并对所设计的ANN进行了训练和验证,仿真实验结果表明,所设计的ANN能够在统计意义上逼真地模拟样本数据,从而使基于ANN的模拟器信号状态参量计算能够满足设计要求,可以直接应用于多通道GPS信号模拟器的研制。   << 更多相关文摘 
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