地基宽带分布式全相参雷达技术研究

发布时间：2018-09-14 12:38

【摘要】：为了增大雷达探测威力、提高雷达探测精度,通常采用增大雷达天线口径的方式。而传统大口径雷达存在机动部署困难、战场生存能力差、制造成本昂贵、对器件的工艺水平要求苛刻、后期难以维护等问题,这些问题极大地限制了其发展与应用。为了克服传统大孔径雷达的固有缺陷,林肯实验室提出了分布式全相参雷达的概念,该雷达通过对多部小孔径单元雷达进行信号级的融合处理,使其在性能上等效于大孔径雷达。目前,研究人员对分布式全相参雷达的研究还处于起步探索阶段,实现该体制雷达的关键技术尚待解决。本文系统分析了分布式全相参雷达的结构组成和工作流程;针对实现分布式宽带全相参所面临的关键问题,提出了基于正交信号和相参信号的相参参数估计方法、基于内外定标的系统同步方法以及基于频率步进信号的宽带全相参方法;结合分布式系统多单元雷达的阵列结构,研究了一种对抗雷达主瓣干扰的有效方法。论文的主要研究内容和成果如下:1、在分布式全相参雷达中,由于各单元雷达与目标的距离不同,导致各发射信号在目标处存在时间差和相位差,本文将这两个参数合称为相参参数。为了实现雷达的全相参工作,要求各单元雷达发射信号应在目标处相参叠加,因此需要准确获取相参参数。本文研究了相参参数的估计方法:首先,介绍了分布式全相参雷达的系统组成,详细给出了其工作流程,并根据各单元雷达与目标的相对位置关系,建立了相参参数的数学模型;然后,对应分布式系统的工作流程,分别提出了基于正交信号的相参参数估计方法和基于相参信号的相参参数估计方法,为了提高相参参数的估计精度,提出了基于修正代价函数的正交多相编码信号的波形设计方法,并针对两种信号的相参参数,分别推导了其克拉美-罗下界(Cramer Rao Low Bound,CRLB),对两种估计方法的估计性能进行了仿真分析;最后,为了对运动目标的相参参数进行有效地跟踪,提出了基于Kalman的相参参数滤波方法,并通过仿真验证了该方法的有效性。相参参数是实现分布式雷达全相参工作的关键参数,通过对分布式雷达相参参数估计方法的研究,为实现系统全相参提供了技术支撑。2、分布式系统的时间和相位同步误差将导致相参参数估计值存在偏差,进而降低系统的相参性能。本文针对分布式全相参雷达的系统同步问题,提出了基于内、外定标的分布式系统时间同步和相位同步方法。首先,分析了系统同步误差的来源,建立了时间同步误差和相位同步误差的数学模型,分析了同步误差对系统相参性能的影响,在一定相参性能损失的前提下给出了分布式全相参雷达对时间同步误差及相位同步误差的指标要求;然后,在设计了系统本振同源方案的基础上,提出了基于内、外定标的系统时间同步和相位同步方法,即:采用中心站向各单元雷达分发信号的方式构成各单元雷达的本振信号,以消除晶振源频率准确度及稳定度对同步误差带来的影响,在此基础上,分别基于内、外定标的方式对时间同步误差和相位同步误差进行估计,并利用同步误差估计值对雷达发射信号进行补偿以最终实现系统同步,仿真结果验证了所提同步方法的有效性。系统同步是实现分布式雷达全相参工作的前提,通过对分布式全相参雷达系统同步方法的研究,为实现系统全相参奠定了基础。3、为了适应现代雷达对距离高分辨率的要求,需要对宽带分布式全相参雷达进行研究。针对宽带分布式系统中时间同步误差会严重降低系统相参性能的问题,本文提出了基于频率步进信号的宽带全相参技术,以提高系统对时间同步误差的鲁棒性。首先,基于频率步进信号瞬时窄带合成宽带的特性,提出采用调频步进信号代替传统线性调频信号作为分布式全相参雷达的发射信号,能够在保证宽带雷达高测量性能的前提下提高分布式系统对时间同步误差的鲁棒性,从而降低宽带分布式系统对时间同步精度的要求;然后,为了对分布式全相参雷达的相参性能进行定量分析,定义了发射相参效率和全相参效率。由于实际雷达系统工作时两单元雷达回波信噪比不相同,进而导致原理想全相参回波信噪比计算方法不再适用,故分析推导了该场景下理想全相参回波信噪比的计算公式,并对应给出了发射相参效率和全相参效率的计算方法;最后,为了对基于频率步进信号的宽带全相参技术进行实验验证,本文研制了分布式全相参雷达实验系统原理样机,利用实验系统开展了基于调频步进宽带全相参暗室及外场实验,并取得了良好的结果,从而在仿真验证的基础上,进一步利用实测数据证明了所提方法的有效性。宽带雷达是现代雷达发展的必然趋势,通过对宽带分布式全相参技术的研究,为分布式系统的未来发展提供了技术支撑。4、针对雷达主瓣干扰这一难题,结合分布式系统多单元雷达的阵列结构,本文研究了基于大孔径辅助接收阵列的主瓣干扰抑制方法,借助大孔径阵列的空间高分辨率优势,利用辅助阵列接收的干扰数据对消主雷达的主瓣干扰。首先,针对辅助阵列均匀间隔的布阵方式,对辅助阵列总长度、阵列雷达间距及单元雷达个数进行了设计;然后,利用辅助阵列接收的干扰信号与主雷达接收的干扰信号之间的相关性,基于最小均方误差(Minimum Mean Square Error,MMSE)准则和最大信干噪比(Maximum Signal to Interference plus Noise Ratio,MSINR)准则,分别提出了两种抑制主瓣干扰的自适应波束形成方法;此外,由于辅助阵列的均匀稀疏特性导致其阵列方向图中存在较高的栅瓣,故采用非均匀间隔布阵的方式以降低栅瓣电平,并在最小单元雷达间距和最大阵列长度的限制条件下提出了基于修正遗传算法的阵列间距设计方法,对辅助阵列间距进行了重新设计;最后,利用所提方法对含有干扰成分的雷达回波数据进行了处理,仿真验证了所提方法的有效性。通过对分布式雷达对抗主瓣干扰技术的研究,扩展了分布式雷达系统的功能及应用领域。
[Abstract]:In order to increase the detection power and improve the detection precision of radar, the method of enlarging the antenna aperture is usually adopted. However, the traditional large-aperture radar has some problems, such as difficult maneuvering deployment, poor battlefield survivability, high manufacturing cost, strict requirements for the technological level of the device, and difficult maintenance in the later period, which greatly restrict its development and development. Application. In order to overcome the inherent defects of traditional large aperture radar, Lincoln Laboratory put forward the concept of distributed all-coherent radar, which is equivalent to large aperture radar in performance by fusing several small aperture unit radars at signal level. In the initial exploration stage, the key technology to realize this radar system remains to be solved. This paper systematically analyzes the structure and work flow of distributed all-coherent radar, and proposes a coherent parameter estimation method based on orthogonal signal and coherent signal, and a system based on internal and external calibration. The main contents and achievements of this paper are as follows: 1. In distributed all-coherent radar, due to the different distances between the radar and the target, each unit has its own characteristics. In order to realize the coherent operation of the radar, it is necessary to obtain the coherent parameters accurately. This paper studies the estimation method of the coherent parameters. The system composition of distributed all-coherent radar is given in detail, and the mathematical model of coherent parameters is established according to the relative position relationship between each unit radar and target. Then, corresponding to the workflow of distributed system, the estimation method of coherent parameters based on orthogonal signals and the phase based on coherent signals are proposed respectively. In order to improve the estimation accuracy of coherent parameters, a waveform design method for orthogonal polyphase coded signals based on modified cost function is proposed. Cramer Rao Low Bound (CRLB) is derived for the coherent parameters of the two signals, and the estimation performance of the two methods is simulated. Finally, in order to track the coherent parameters of moving targets effectively, a Kalman-based filtering method of coherent parameters is proposed, and the effectiveness of this method is verified by simulation. Coherent parameters are the key parameters to realize the full coherent work of distributed radar, and the method of estimating the coherent parameters of distributed radar is studied. All-coherent system provides technical support. 2. The time and phase synchronization errors of distributed system will lead to the deviation of the estimation of coherent parameters, and then reduce the coherence performance of the system. Firstly, the source of system synchronization error is analyzed, the mathematical models of time synchronization error and phase synchronization error are established, the influence of synchronization error on system coherence is analyzed, and the index requirements of time synchronization error and phase synchronization error for distributed all-coherent radar are given under the premise of a certain loss of coherence performance. Then, based on the design of the system local oscillator homology scheme, a method of time synchronization and phase synchronization based on internal and external calibration is proposed, that is, the local oscillator signal of each unit radar is formed by the way that the central station distributes signals to each unit radar, so as to eliminate the influence of the frequency accuracy and stability of crystal oscillator on the synchronization error. On this basis, the time synchronization error and phase synchronization error are estimated based on internal and external calibration respectively, and the synchronization error estimation is used to compensate the radar transmitted signal to realize the system synchronization. The simulation results verify the effectiveness of the proposed synchronization method. The premise is that the research on the synchronization method of distributed all-coherent radar system lays a foundation for the realization of all-coherent radar system. 3. In order to meet the requirements of modern radar for high range and high resolution, it is necessary to study wideband distributed all-coherent radar. In order to improve the robustness of the system to the time synchronization error, a wideband all-coherent technique based on stepped-frequency signal is proposed. Firstly, based on the characteristics of instantaneous narrowband synthesis of stepped-frequency signal, stepped-frequency signal is proposed to replace the traditional linear frequency modulation signal as the transmitting signal of distributed all-coherent radar. It can improve the robustness of the distributed system to the time synchronization error while ensuring the high measurement performance of the wideband radar, so as to reduce the requirement of the time synchronization precision of the wideband distributed system. The difference of signal-to-noise ratio between two radar echoes in the operation of an international radar system leads to the inapplicability of the method for calculating the signal-to-noise ratio of the ideal fully coherent echoes in principle. Therefore, the formulas for calculating the signal-to-noise ratio of the ideal fully coherent echoes in this scenario are analyzed and deduced, and the methods for calculating the transmitting coherence efficiency and the total coherence efficiency are given correspondingly. Based on the wide-band all-coherent technology of stepped-frequency signal, the principle prototype of distributed all-coherent radar experimental system is developed. The experiments of wide-band all-coherent darkroom and outfield based on stepped-frequency modulation are carried out by using the experimental system, and good results are obtained. On the basis of simulation and verification, the measured data are further utilized. It is proved that the proposed method is effective. Broadband radar is the inevitable trend of modern radar development. Through the research of wideband distributed all-coherent technology, it provides technical support for the future development of distributed system. 4. Aiming at the problem of radar main lobe jamming, combined with the array structure of distributed system multi-unit radar, this paper studies based on The main lobe jamming suppression method of large aperture auxiliary receiving array is proposed. With the advantage of high spatial resolution of large aperture array, the main lobe jamming of the main radar is cancelled by the jamming data received by the auxiliary array. Firstly, the total length of the auxiliary array, the spacing of the array radar and the number of unit radars are calculated according to the uniform spacing of the auxiliary array. Then, based on the correlation between the jamming signal received by the auxiliary array and the jamming signal received by the main radar, two kinds of self-restraining methods for the main lobe jamming are proposed, respectively, based on the minimum mean square error (MMSE) criterion and the maximum signal to interference plus Noise Ratio (MSINR) criterion. In addition, due to the uniform sparse characteristic of the auxiliary array, there are high grating lobes in the array pattern, so the non-uniform spaced array is used to reduce the grating lobe level, and the array spacing based on the modified genetic algorithm is proposed under the restriction of the minimum element radar spacing and the maximum array length. Finally, the method is used to process the radar echo data with jamming components, and the effectiveness of the proposed method is verified by simulation. Through the research of distributed radar countering main lobe jamming technology, the functions and application fields of distributed radar system are extended.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN957.51

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