局域增强系统(L oca l A rea A ugm en ta tion System,LAA S)是美国联邦航空局(F ed era l A v ia tion A d-m in istra tion,FAA)开发的G PS地基增强系统,支持G PS差分精密进近和着陆.多基准一致性检测是LAA S地面完好性监测的核心算...局域增强系统(L oca l A rea A ugm en ta tion System,LAA S)是美国联邦航空局(F ed era l A v ia tion A d-m in istra tion,FAA)开发的G PS地基增强系统,支持G PS差分精密进近和着陆.多基准一致性检测是LAA S地面完好性监测的核心算法.多基准一致性检测通过对伪距校正误差的测试和评估,保证了LAA S地面系统发布的伪距校正量误差不超出一个给定的范围.本文详细讨论了LAA S完好性监测模型中多基准一致性检测算法的B值的含义,并通过实验分析了B值的范围和阈值的选取.结果表明:在正常无故障情况下,B值的大小稳定在一个较小的范围内变化.一旦发生故障,通过阈值的限制就能检测出B值异常的情况.展开更多
为了满足民用航空用户在精密进场与着陆中的应用需求,美国联邦航空管理局设计了GPS局域增强系统(Local Area Augmention System,LAAS)。LAAS地面站设备采用3-4个安装在机场固定已知点的高性能GPS接收机,观测所有可见卫星,并将这些观测...为了满足民用航空用户在精密进场与着陆中的应用需求,美国联邦航空管理局设计了GPS局域增强系统(Local Area Augmention System,LAAS)。LAAS地面站设备采用3-4个安装在机场固定已知点的高性能GPS接收机,观测所有可见卫星,并将这些观测数据同时发送给处理单元,处理单元将码相位测量的伪距数据进行载波相位平滑,同时使用差分技术获得每颗可用卫星的误差修正值,并进行完善性监测,最后利用甚高频(VHF)广播这些修正数据。当某颗卫星出现故障后,整个系统的可用性发生改变。通过仿真研究可以得到当可见卫星数量在6颗或6颗以上时,减少一个卫星对完善性影响不大,甚至会变好,在可见卫星为5颗的时候较少一个完善性的可用性降低。并且完善性还和卫星的几何分布有关。展开更多
In this paper, effects on DOP (Dilution of Precision) due to augmentation of Global Positioning System (GPS) with pseudolites are investigated. For this purpose, a typical Local Area Augmentation System (LAAS) scenari...In this paper, effects on DOP (Dilution of Precision) due to augmentation of Global Positioning System (GPS) with pseudolites are investigated. For this purpose, a typical Local Area Augmentation System (LAAS) scenario is consi-dered by placing pseudolites in various positions. It is found that only properly located pseudolites can improve the DOP. DOP values with two pseudolites located on either side of the run way are found to be the best. Geometric DOP (max) was found to be nearly 4 due to only GPS and came down to approximately 2 due to augmentation with two pseudolites. Implementation aspects of Bayes and Kalman filters while estimating DOP values are also examined.展开更多
Side lobe level reduction(SLL)of antenna arrays significantly enhances the signal-to-interference ratio and improves the quality of service(QOS)in recent and future wireless communication systems starting from 5G up t...Side lobe level reduction(SLL)of antenna arrays significantly enhances the signal-to-interference ratio and improves the quality of service(QOS)in recent and future wireless communication systems starting from 5G up to 7G.Furthermore,it improves the array gain and directivity,increasing the detection range and angular resolution of radar systems.This study proposes two highly efficient SLL reduction techniques.These techniques are based on the hybridization between either the single convolution or the double convolution algorithms and the genetic algorithm(GA)to develop the Conv/GA andDConv/GA,respectively.The convolution process determines the element’s excitations while the GA optimizes the element spacing.For M elements linear antenna array(LAA),the convolution of the excitation coefficients vector by itself provides a new vector of excitations of length N=(2M−1).This new vector is divided into three different sets of excitations including the odd excitations,even excitations,and middle excitations of lengths M,M−1,andM,respectively.When the same element spacing as the original LAA is used,it is noticed that the odd and even excitations provide a much lower SLL than that of the LAA but with amuch wider half-power beamwidth(HPBW).While the middle excitations give the same HPBWas the original LAA with a relatively higher SLL.Tomitigate the increased HPBWof the odd and even excitations,the element spacing is optimized using the GA.Thereby,the synthesized arrays have the same HPBW as the original LAA with a two-fold reduction in the SLL.Furthermore,for extreme SLL reduction,the DConv/GA is introduced.In this technique,the same procedure of the aforementioned Conv/GA technique is performed on the resultant even and odd excitation vectors.It provides a relatively wider HPBWthan the original LAA with about quad-fold reduction in the SLL.展开更多
文摘局域增强系统(L oca l A rea A ugm en ta tion System,LAA S)是美国联邦航空局(F ed era l A v ia tion A d-m in istra tion,FAA)开发的G PS地基增强系统,支持G PS差分精密进近和着陆.多基准一致性检测是LAA S地面完好性监测的核心算法.多基准一致性检测通过对伪距校正误差的测试和评估,保证了LAA S地面系统发布的伪距校正量误差不超出一个给定的范围.本文详细讨论了LAA S完好性监测模型中多基准一致性检测算法的B值的含义,并通过实验分析了B值的范围和阈值的选取.结果表明:在正常无故障情况下,B值的大小稳定在一个较小的范围内变化.一旦发生故障,通过阈值的限制就能检测出B值异常的情况.
文摘为了满足民用航空用户在精密进场与着陆中的应用需求,美国联邦航空管理局设计了GPS局域增强系统(Local Area Augmention System,LAAS)。LAAS地面站设备采用3-4个安装在机场固定已知点的高性能GPS接收机,观测所有可见卫星,并将这些观测数据同时发送给处理单元,处理单元将码相位测量的伪距数据进行载波相位平滑,同时使用差分技术获得每颗可用卫星的误差修正值,并进行完善性监测,最后利用甚高频(VHF)广播这些修正数据。当某颗卫星出现故障后,整个系统的可用性发生改变。通过仿真研究可以得到当可见卫星数量在6颗或6颗以上时,减少一个卫星对完善性影响不大,甚至会变好,在可见卫星为5颗的时候较少一个完善性的可用性降低。并且完善性还和卫星的几何分布有关。
文摘In this paper, effects on DOP (Dilution of Precision) due to augmentation of Global Positioning System (GPS) with pseudolites are investigated. For this purpose, a typical Local Area Augmentation System (LAAS) scenario is consi-dered by placing pseudolites in various positions. It is found that only properly located pseudolites can improve the DOP. DOP values with two pseudolites located on either side of the run way are found to be the best. Geometric DOP (max) was found to be nearly 4 due to only GPS and came down to approximately 2 due to augmentation with two pseudolites. Implementation aspects of Bayes and Kalman filters while estimating DOP values are also examined.
基金Research Supporting Project Number(RSPD2023R 585),King Saud University,Riyadh,Saudi Arabia.
文摘Side lobe level reduction(SLL)of antenna arrays significantly enhances the signal-to-interference ratio and improves the quality of service(QOS)in recent and future wireless communication systems starting from 5G up to 7G.Furthermore,it improves the array gain and directivity,increasing the detection range and angular resolution of radar systems.This study proposes two highly efficient SLL reduction techniques.These techniques are based on the hybridization between either the single convolution or the double convolution algorithms and the genetic algorithm(GA)to develop the Conv/GA andDConv/GA,respectively.The convolution process determines the element’s excitations while the GA optimizes the element spacing.For M elements linear antenna array(LAA),the convolution of the excitation coefficients vector by itself provides a new vector of excitations of length N=(2M−1).This new vector is divided into three different sets of excitations including the odd excitations,even excitations,and middle excitations of lengths M,M−1,andM,respectively.When the same element spacing as the original LAA is used,it is noticed that the odd and even excitations provide a much lower SLL than that of the LAA but with amuch wider half-power beamwidth(HPBW).While the middle excitations give the same HPBWas the original LAA with a relatively higher SLL.Tomitigate the increased HPBWof the odd and even excitations,the element spacing is optimized using the GA.Thereby,the synthesized arrays have the same HPBW as the original LAA with a two-fold reduction in the SLL.Furthermore,for extreme SLL reduction,the DConv/GA is introduced.In this technique,the same procedure of the aforementioned Conv/GA technique is performed on the resultant even and odd excitation vectors.It provides a relatively wider HPBWthan the original LAA with about quad-fold reduction in the SLL.
