In this paper the authors explore the Global Positioning System （GPS） signal acquisition and tracking algorithms used in software GPS receiver. Acquisition time is the most important parameter in evaluating the perf...In this paper the authors explore the Global Positioning System （GPS） signal acquisition and tracking algorithms used in software GPS receiver. Acquisition time is the most important parameter in evaluating the performance of a software GPS receiver in terms of its speed. A trade-off study is done to seek a good balance between the acquisition accuracy and the processing time. The frequency-domain acquisition method by circular correlation, used in a software GPS receiver, has been improved by studying the power spectrum of the Coarse Acquisition （C/A） code alone. The analysis of C/A code reveals that its power spectrum is symmetrical; hence only half the points are required to perform circular correlation. Besides, either half of the spectrum is asymmetrical where a larger amount of power is concentrated in almost one-quarter of the spectrum on its either sides. This further reduces the number of points used to perform correlation. Comparative results of MATLAB simulation of full-size, half-size and quarter-size circular correlation done on actual data stored on hard disk are provided, and they agree with those obtained using GPS receiver. Further reduction in acquisition time has been achieved by investigating the effect of length of the noncoherent pre-integration period. The improved acquisition methods pave way for further development of new algorithms to enhance software GPS receiver performance.展开更多
针对弱信号条件下GPS C/A码捕获问题,提出一种基于平均相关和差分相干累积的码捕获算法。首先,引入相干能量最大值与第二大值的比值作为判决变量,仿真了各种捕获算法的虚警概率得到最佳的判决门限;然后,通过设置的判决门限获得不同多普...针对弱信号条件下GPS C/A码捕获问题,提出一种基于平均相关和差分相干累积的码捕获算法。首先,引入相干能量最大值与第二大值的比值作为判决变量,仿真了各种捕获算法的虚警概率得到最佳的判决门限;然后,通过设置的判决门限获得不同多普勒频率偏差及信噪比条件下的检测概率;最后,比较了所提差分相干累积算法、相干非相干累积算法以及非相干累积算法的捕获灵敏度。仿真实验表明,在相同接收数据长度的情况下,采用差分相干累积算法比其他2种算法提高捕获灵敏度约2 d B。展开更多
The global positioning system(GPS) is an extremely mature technique in the navigation and position-ing field.However,there are still some limits in some aspects and for some special applications.Spe-cially,the perform...The global positioning system(GPS) is an extremely mature technique in the navigation and position-ing field.However,there are still some limits in some aspects and for some special applications.Spe-cially,the performance of GPS needs to be improved with technological advances.As a GPS-like ground transmitter,the pseudolite provides a new research direction to achieve high positioning ac-curacy and reliability.In this paper,we describe the core technologies of designing and simulation on the coarse acquisition codes in constructing the pseudolite system.In the GPS/pseudolite integration system,the signal PRN 36 of the pseudolite and the GPS satellites signals are acquired in the modified receiver based on the computer software platform.It is shown that the pseudolite technology is ideally suited to augment the GPS alone and provide greater integrity,availability,and continuity of the navi-gation positioning system,especially for indoor use.展开更多
为提高GPS接收机在低信噪比环境中的捕获精度和灵敏度,提出了一种新的弱信号精捕获算法。该算法采用差分相干积分缓解平方损耗,并利用积分结果的相位信息修正载波频率,使其估计精度不再受到频移搜索步长的限制。此外,该算法根据载波多...为提高GPS接收机在低信噪比环境中的捕获精度和灵敏度,提出了一种新的弱信号精捕获算法。该算法采用差分相干积分缓解平方损耗,并利用积分结果的相位信息修正载波频率,使其估计精度不再受到频移搜索步长的限制。此外,该算法根据载波多普勒和码多普勒的比例关系,直接对本地码相位进行校正,保证了信号积累时间较长时不同相关峰之间的重叠性,有助于提高捕获灵敏度并能够得到接收信号末端精确的码相位。仿真结果表明,载波频率和码相位的估计误差分别小于20 Hz和1个采样点,在给定的信号积累时间下,本地码相位校正对捕获灵敏度的提升可达3.2 d B。展开更多
文摘In this paper the authors explore the Global Positioning System （GPS） signal acquisition and tracking algorithms used in software GPS receiver. Acquisition time is the most important parameter in evaluating the performance of a software GPS receiver in terms of its speed. A trade-off study is done to seek a good balance between the acquisition accuracy and the processing time. The frequency-domain acquisition method by circular correlation, used in a software GPS receiver, has been improved by studying the power spectrum of the Coarse Acquisition （C/A） code alone. The analysis of C/A code reveals that its power spectrum is symmetrical; hence only half the points are required to perform circular correlation. Besides, either half of the spectrum is asymmetrical where a larger amount of power is concentrated in almost one-quarter of the spectrum on its either sides. This further reduces the number of points used to perform correlation. Comparative results of MATLAB simulation of full-size, half-size and quarter-size circular correlation done on actual data stored on hard disk are provided, and they agree with those obtained using GPS receiver. Further reduction in acquisition time has been achieved by investigating the effect of length of the noncoherent pre-integration period. The improved acquisition methods pave way for further development of new algorithms to enhance software GPS receiver performance.
文摘针对弱信号条件下GPS C/A码捕获问题,提出一种基于平均相关和差分相干累积的码捕获算法。首先,引入相干能量最大值与第二大值的比值作为判决变量,仿真了各种捕获算法的虚警概率得到最佳的判决门限;然后,通过设置的判决门限获得不同多普勒频率偏差及信噪比条件下的检测概率;最后,比较了所提差分相干累积算法、相干非相干累积算法以及非相干累积算法的捕获灵敏度。仿真实验表明,在相同接收数据长度的情况下,采用差分相干累积算法比其他2种算法提高捕获灵敏度约2 d B。
基金Supported by the Start-up Research Foundation of the Dean Excellent Award of Chinese Academy of Sciences.
文摘The global positioning system(GPS) is an extremely mature technique in the navigation and position-ing field.However,there are still some limits in some aspects and for some special applications.Spe-cially,the performance of GPS needs to be improved with technological advances.As a GPS-like ground transmitter,the pseudolite provides a new research direction to achieve high positioning ac-curacy and reliability.In this paper,we describe the core technologies of designing and simulation on the coarse acquisition codes in constructing the pseudolite system.In the GPS/pseudolite integration system,the signal PRN 36 of the pseudolite and the GPS satellites signals are acquired in the modified receiver based on the computer software platform.It is shown that the pseudolite technology is ideally suited to augment the GPS alone and provide greater integrity,availability,and continuity of the navi-gation positioning system,especially for indoor use.
文摘为提高GPS接收机在低信噪比环境中的捕获精度和灵敏度,提出了一种新的弱信号精捕获算法。该算法采用差分相干积分缓解平方损耗,并利用积分结果的相位信息修正载波频率,使其估计精度不再受到频移搜索步长的限制。此外,该算法根据载波多普勒和码多普勒的比例关系,直接对本地码相位进行校正,保证了信号积累时间较长时不同相关峰之间的重叠性,有助于提高捕获灵敏度并能够得到接收信号末端精确的码相位。仿真结果表明,载波频率和码相位的估计误差分别小于20 Hz和1个采样点,在给定的信号积累时间下,本地码相位校正对捕获灵敏度的提升可达3.2 d B。
