【作者】 张琳；

【导师】 张乃通；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2007， 博士

【摘要】 卫星导航定位系统凭借其高精度定位、授时的技术优势和全天候、实时性、连续性和被动式导航定位的工作特点,不仅可广泛应用于公路、铁路、航运、电信、石油、建筑、农业、气象、水利、环保、海洋与土地管理、渔业捕捞、地质勘探、大地测量、旅游、金融、公安、消防等部门和行业,而且可应用在航天器飞行、空间站交汇对接、靶场测控、航空、军事侦察、战场单兵作战系统、智能武器、灵巧炸弹等特殊领域。但是,卫星导航定位信号面临着弱信号强干扰复杂的恶劣信道环境,容易受干扰的重要原因是卫星信号功率小。卫星导航定位系统容易受到其它多种形式的有意和无意干扰,其中主要包括压制式干扰和欺骗式干扰。当存在压制式干扰信号时,由于干扰信号覆盖了卫星导航信号频谱范围,大大降低了接收信号的信噪比,导致定位测速精度急剧下降,并且在多数情况下接收机无法正常捕获跟踪卫星导航信号。当存在欺骗式干扰信号时,由于欺骗式干扰信号的作用,卫星定位结果已经远离真实位置,而通用接收机无法获知定位结果已由于欺骗式干扰信号作用而偏离了真实位置,从而使接收机受到更大的影响。因此,本文针对卫星导航系统容易受到干扰信号的干扰;在压制式干扰影响下,导航定位精度降低,甚至无法正常工作;在欺骗式干扰影响下,导航解算结果偏离真实位置并且接收系统无法察觉的情况,重点研究了卫星导航定位抗干扰接收机系统中的几个关键技术:第一,卫星导航定位系统接收机抗压制式干扰自适应滤波算法研究。卫星导航接收机在存在多个压制干扰源(包括宽带和窄带)的情况下,系统定位精度降低甚至无法满足定位要求。由于压制式宽带干扰信号覆盖了卫星导航信号的整个频谱,传统抗干扰算法采用阵列天线空域滤波算法或空时联合滤波算法,然而由于在对压制式宽带干扰信号大幅度抑制的同时,与干扰信号空间角谱接近的卫星导航信号也被同时极大衰减,在可见卫星有限的条件下,降低了卫星导航系统性能。因此,本文提出具有方向约束条件的改进联合空时滤波处理算法,将干扰源来向检测和获取的导航卫星信息作为条件约束判据引入联合空时滤波处理算法,该算法的特点在于具有较高的干扰抑制度、抗干扰自由度(可同时抑制的干扰数目),特别是在卫星导航信号和干扰信号空间角谱接近的情况下,在抑制干扰信号的同时保证靠近干扰源来向的卫星信号的正常接收。仿真表明,在有限阵元规模情况下,该算法可以保证干扰信号的高抑制度,并且提高干扰抑制自由度,最重要的是当导航卫星信号与干扰信号的空间角谱接近时(大于10°左右),在有效抑制干扰的同时接收机仍然能够正常工作,尤其针对我国卫星导航系统建设初期,可用卫星数目有限的条件下,该处理算法具有更大的应用价值。第二,抗欺骗式干扰方案设计,其中包括两个方面:欺骗式干扰特征判别处理方法研究和抗欺骗式干扰定位解算算法研究。首先,欺骗式干扰特征判别处理方法是从干扰信号特征上判别并剔除具有明显干扰信号特征的欺骗式干扰信号。其次,对于无法通过上一步骤识别并剔除的高质量欺骗式干扰,在定位解算过程中采用改进扩展卡尔曼滤波算法滤除欺骗式干扰的干扰作用。该改进抗欺骗式干扰扩展卡尔曼滤波算法,结合了稳健统计理论中的M-估计算法,通过M-估计产生的加权量来调整卡尔曼滤波器的状态更新过程,以获得更为精确的状态估计,消除欺骗干扰的影响,提高接收机的抗欺骗干扰性能。并根据卫星导航接收机工程实现需要,简化了M-估计算法产生的衰减因子的计算方法。仿真表明,通过对比最小二乘、传统卡尔曼滤波定位解算算法和本文算法,本文算法可以有效地消除欺骗式干扰的影响(欺骗式干扰信号引起的伪距测量误差1200m),具有较高的定位测速精度,定位精度优于10m、测速精度优于0.5m/s(以GPS系统为例),并且算法实现复杂度较低,更加有利于卫星导航系统抗欺骗式干扰接收机工程化实现。D(e )第三,卫星导航接收机的抗干扰改进设计。不同于传统卫星导航接收机,本文设计改进卫星导航接收机针对压制式干扰信号和欺骗式干扰信号,给出了抗干扰接收机中频信号处理及信息处理方案,其核心仿真模块主要包括抗压制式干扰模块、抗欺骗式干扰模块,并且给出卫星信号捕获跟踪模块设计。通过考察抗压制式干扰信号处理模块输出信噪比结果、卫星信号捕获跟踪输出结果和抗欺骗式干扰导航定位测速输出结果,系统仿真对比传统卫星导航接收机和本文设计改进卫星导航接收机的抗干扰性能。仿真结果表明,本文设计的抗干扰接收机方案,可以有效的抑制压制式干扰的影响,滤除欺骗式干扰的作用,具有良好的信号捕获跟踪性能,和较高的定位测速精度,具备一定的抗干扰能力。更多还原

【Abstract】 Satellite navigation system is widely used in the area of highway, railway, maritime navigation, telecommunication, petroleum exploration, construction, agriculture, meteorology, hydraulics, environmental protection, oceanography, estate administration, fishing industry, geological prospecting, geodetic surveying, tourism, finance, public security, fire protection, etc, and in the area of spacecraft, space station docking, shooting range monitoring, aviation, military reconnaissance, field single soldier battle system, intelligent weapon, dexterity bomb, etc as well, since it can provide high accuracy positioning and timing with the navigation characteristic of 24-hour service, real time, continuity and passivity. Nevertheless, satellite navigation signals are so weak that they are susceptible to kinds of interferences in face with complicated channel environment of weak satellite signal and strong interferences. As a result, the satellite navigation system is susceptible to both the intentional and unintentional interferences, including jamming and spoofing. When there come jamming interferences, jamming signal cover the whole frequency spectrum of the satellite signal, and greatly reduce the signal to noise ratio, with the result that the navigation accuracy of position and velocity decrease seriously, and the navigation receiver is unable to capture and track the satellite signal in most cases. When there come spoofing interferences, the navigation solution deviates from the truth, and since the receiver is unable to perceive the deviation, the spoofing interferences bring about great calamity. Therefore, this dissertation research on several key techniques in the satellite navigation anti-interference (including jamming and spoofing interferences) receiver with respect to the fact that the satellite navigation system is vulnerable to the interferences, the jamming interferences lead to the low accuracy of navigation solution for normal operation, and the spoofing interferences lead to the deviation of navigation solution from the truth, while the receiver is unsuspicious.Firstly, Research on anti-jamming adaptive filter for the satellite navigation receiver. When there exist multiple jamming interferences (including broadband and narrowband), the accuracy of the navigation solution decreased below the normal level. Since the jamming signals cover the whole frequency spectrum of the navigation signals, traditional anti-jamming algorithm using the adaptive antenna array or space time adaptive processing algorithm. Nevertheless, as the jamming signal is greatly suppressed, the satellite signal which has similar direction of arrival with jamming is depressed simultaneously, and thus depresses the system performance with limited visible satellites. Therefore, this dissertation proposes improved space time adaptive processing algorithm with direction restriction obtained from the direction detection and estimation of the jamming and the satellite information. The algorithm has the characteristics of high degree of interference suppression and high degree of freedom (amount of interferences suppressed simultaneously), especially when the satellite signal and jamming has similar direction, the satellite signal could be received normally, while the jamming is suppressed greatly. Simulation suggests that the jamming signal is suppressed more than 40 dB, and the degree of freedom is increased with finite antenna array scale, especially when the satellite signal and the jamming signal have similar direction of less than 10°, the receiver is able to operate normally while the jamming signal is depressed, which is profitable when the satellite navigation system is built at preliminary stage and the visible satellite is limited.Secondly, Design of anti-spoofing processing for satellite navigation receiver, including two aspects: spoofing signal characteristics discrimination method research and anti-spoofing navigation solution research. First of all, discriminate the spoofing signals with concern of the characteristics of spoofing signals. And then propose an improved extended Kalman filter algorithm in the navigation solution process for the high quality spoofing signals which can not been discriminated. The proposed improved anti-spoofing extended Kalman filter algorithm make use of the M-estimator of robust statistics, and adapt the innovation process of extended Kalman filter with the simplified weighted factor produced in the M-estimator, which reduces the computational complexity while maintaining the accuracy of the navigation solution and improve the anti-spoofing performance of receiver, and thus is beneficial to the realization of the algorithm in the project. Simulation suggests that in comparison with the conventional snapshot least square algorithm and the conventional extended Kalman filter, the proposed anti-spoofing extended Kalman filter is able to reduce the deviation of the navigation solution caused by the spoofing signals (the pseudorange measurement error caused by spoofing signal is 1200m) with higher navigation solution accuracy with position precision is above 10m and velocity precision is above 0.5m/s (GPS as example), and less computational complexity.Thirdly, improvement design of satellite navigation receiver with the ability of anti-interference. In comparison with traditional satellite navigation receiver, the paper proposes an improved design of satellite navigation receiver with the ability of anti-jamming and anti-spoofing, and also proposes the designs of both the medial frequency signal processing and the information processing, including the anti-jamming module, the anti-spoofing module and the satellite signal capture and tracking module. Simulations compare the traditional satellite navigation receiver with the proposed anti-interference receiver in the aspect of signal to noise ratio of anti-jamming signal processing module, performance of satellite signal capture and tracking module, and navigation position and velocity solution accuracy of anti-spoofing module, which suggests that the anti-interference (including jamming and spoofing) receiver proposed is able to effectively suppress jamming and spoofing signals, credibly capture and track satellite signals and have higher accuracy of navigation solution in position and velocity, which indicates that the proposed anti-interference receiver is provided with certain capability of anti-jamming and anti-spfooing.更多还原