北斗接收机空时自适应抗干扰技术研究

发布时间：2018-10-20 10:46

【摘要】：北斗卫星导航系统是中国自主研制的卫星导航系统,因其能提供全天候、全方位的导航、定位、授时,短报文服务,在国防和经济建设中发挥了重要作用。近年来,全球卫星导航系统更是在世界各个国家得到迅速的普及和应用。但是由于卫星信号功率很低,军事上经常存在敌方的有意电磁波干扰以及卫星导航应用电磁波环境的日益复杂,导航终端很容易受到干扰信号的影响而无法正常工作。因此,目前各国都很重视卫星导航系统抗干扰技术的研究。在此背景下,研究导航接收机抗干扰技术具有非常重要的意义。传统的接收机抗干扰技术分别从时域、频域以及空域三个方面对信号进行处理。时域处理算法比较复杂,自适应性较差;频域处理算法能够有效地抑制窄带干扰,但在抑制宽带干扰时会严重削弱有用信号;纯空域算法能够处理的干扰数目受限于阵元个数。因此,本文采用空时联合滤波STAP技术来对接收到的导航信号进行自适应处理。该技术能够在不增加天线阵元个数的情况下,通过空域与时域相结合的方式增加处理信号源的个数和种类,大大提高了接收机的抗干扰能力。传统的STAP技术在性能上有两方面的不足:(1)算法需要对观测信号进行协方差矩阵的求逆运算,计算量大,计算复杂度高;(2)需要预先估计期望信号的先验信息,当估计的先验信息出现误差时,会使接收到的卫星信号功率衰减,甚至使接收机丧失定位导航能力。针对传统的STAP技术计算复杂度高的问题,本文利用改进的两步迭代变步长最小均方误差(LMS)算法以及改进的变遗忘因子递归最小二乘(RLS)算法对空时滤波器的加权值进行计算,从而降低计算复杂度;针对空时滤波技术先验信息不准确的问题,本文提出利用矢量跟踪环输出的导航信号作为空时滤波算法的参考信息,由于不需要提前估计先验信息,大大提高了算法的稳健性;本文还研究了在空时滤波器的A/D输出端添加频域LMS滤波器的方法来抑制与导航信号的同方向的窄带干扰,从而增强导航接收机的干扰抑制能力。最后,通过现有的接收机平台采集导航数据,并对实测数据进行抗干扰处理,验证了本文所提算法能够使算法的计算量降低,稳健性提高,最终使导航接收机的干扰抑制性能增强。
[Abstract]:Beidou satellite navigation system is a satellite navigation system independently developed by China. It plays an important role in national defense and economic construction because it can provide all-weather, omnidirectional navigation, positioning, time service and short message service. In recent years, the global satellite navigation system has been popularized and applied rapidly in every country of the world. However, because the satellite signal power is very low, the military often exists the enemy's intentional electromagnetic wave interference and the satellite navigation application electromagnetic wave environment is increasingly complex, the navigation terminal is easily affected by the interference signal and can not work normally. Therefore, many countries attach great importance to the research of anti-jamming technology of satellite navigation system. Under this background, it is very important to study the anti-jamming technology of navigation receiver. The traditional receiver anti-jamming technology processes the signal in time domain, frequency domain and spatial domain respectively. The time domain processing algorithm is more complex and the adaptive ability is poor; the frequency domain processing algorithm can effectively suppress narrowband interference, but it will seriously weaken the useful signal when suppressing the wideband interference; the pure spatial domain algorithm can deal with the number of interference limited by the number of array elements. Therefore, the space-time joint filtering (STAP) technique is used to process the received navigation signal adaptively. Without increasing the number of antenna array elements, the technique can increase the number and types of signal sources by combining spatial domain and time domain, and greatly improve the anti-jamming ability of the receiver. The traditional STAP technique has two shortcomings in performance: (1) the algorithm needs to perform covariance matrix inversion of the observed signal, which requires a large amount of computation and high computational complexity; (2) the prior information of the desired signal needs to be estimated in advance. When the estimated prior information errors occur, the received satellite signal power will be attenuated, and even the receiver will lose the positioning and navigation ability. Aiming at the problem of high computational complexity of traditional STAP technique, this paper calculates the weighted value of space-time filter by using the improved two-step iterative variable step size minimum mean square error (LMS) algorithm and the improved variable forgetting factor recursive least square (RLS) algorithm. In order to reduce the computational complexity, aiming at the problem of inaccurate prior information of space-time filtering technology, this paper proposes to use the navigation signal output from vector tracking loop as the reference information of space-time filtering algorithm, because there is no need to estimate prior information in advance. The robustness of the algorithm is greatly improved, and the method of adding frequency-domain LMS filter to the A / D output of space-time filter is studied to suppress the narrowband interference in the same direction as the navigation signal, so as to enhance the interference suppression ability of the navigation receiver. Finally, through the existing receiver platform to collect navigation data, and the anti-jamming processing of the measured data, it is verified that the algorithm proposed in this paper can reduce the calculation amount and improve the robustness of the algorithm. Finally, the interference suppression performance of the navigation receiver is enhanced.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN965.5

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