【作者】 彭卫；

【导师】 汪学刚；

【作者基本信息】 电子科技大学 ， 信号与信息处理， 2010， 博士

【摘要】 高分辨距离像反映了沿雷达径向目标后向散射密度的几何结构分布,较之于二维或三维所成像,高分辨距离像需要更少的计算量,因而更容易获取。基于此,距离维高分辨雷达是提供全天候情况下的目标识别及战场情况感知能力的最佳候选。为了获得高分辨距离像,雷达系统必须拥有处理大带宽信号的能力。但在目前,宽带雷达在宽带信号产生、目标运动补偿、空域自适应处理等方面的相关理论尚不成熟。本文在前人工作的基础上,着重对高分辨合成距离像及其时域及空域的处理作了较深入的研究,并提出了一些创新的算法。这些算法在多组仿真的基础上进行了验证。归纳起来,本文的主要内容包括以下几个方面:1.合成宽带波形处理研究在分析了多种合成宽带信号特性的基础上,构建了处理合成宽带波形的通用结构,并提出了一种衡量合成宽带距离像失真度的误差准则和一种误差分析方法。同时,针对不同的合成宽带信号形式,改进了它们的具体处理结构。2.合成宽带信号的时域处理研究构建了合成宽带信号时域处理的统一结构。提出了一种基于合成宽带信号和传统多普勒滤波器组(使用FFT)的成像系统并对其性能进行了详细地分析。理论分析和仿真结果表明,由于多普勒散布效应,随着目标速度的增大,目标的合成距离像将会产生失真,失真包括距离移动和幅度变形。与此同时,两个与距离移动和幅度变形有关的理论公式被推导出,它们能够分别计算出距离的移动值及评估合成距离像的幅度变形程度,并由此得到了最大临界速度;当目标径向速度小于最大临界速度时,目标的幅度失真是在一个可接受的范围内。提出了一种基于速度门的合成宽带滤波器组结构,通过理论分析,获得了该滤波器组成立的临界条件。分析结果进一步表明,为了得到运动目标的可接受失真度的合成距离像,目标径向速度必须小于合成宽带雷达系统中最小的最大不模糊速度。同时,基于这种合成宽带滤波器组结构,一种新的解速度模糊方法被提出。提出了一种子带间变PRF(Pulse Repetition Frequency)方法的合成宽带滤波器组结构。通过合理的参数设置,它不但能在任何速度下保证合成距离像的失真度在可接受范围内,并且还可通过FFT形式来实现,以便获得计算的高效性。3.合成宽带信号的空域自适应处理技术研究构建了合成宽带空域自适应处理的统一结构。提出了一种基于合成宽带信号和传统的干扰+噪声协方差估计值的合成成像系统并对其性能进行了详细地分析。理论分析和仿真结果表明,由于每一个协方差矩阵在每一个子带内是分别独立估计的,目标的合成距离像将会在整个距离范围内产生随机距离旁瓣,其主要是由于噪声方差估计值在不同的子带随机变动而引起的。基于此,提出了两种减轻和消除随机距离旁瓣的方法,一种是对角加载方法,另一种是正交子空间投影法。提出了一种段自适应处理技术,以便简化系统结构和减少计算量;同时,对其性能进行了理论分析。提出了一种变采样率自适应处理方法,并在理论上推导出它的具体实现方式。4.一种使用LFM波形的宽带数字阵列相对时延测量方法提出了一种使用LFM波形的宽带数字阵列相对时延测量方法并对其性能进行了深入的分析。基于Dechirping技术和数字抽取方法,所提出的测量系统能够工作在低的数据率,从而减小了计算量和降低了硬件复杂度。更进一步,通过合理的参数设定和独特的设计结构,能够在一次测量过程中得到多个T/R(Transmit/receive)组件的相对延时值。分析结果表明,测量误差由噪声误差和系统误差组成,它们分别由组件热噪声和多个共存的LFM信号的相互作用而引起,并从理论上推导出该系统的测量精度公式,从而可对一些重要的参量进行评估。基于此,不但可定出测量系统的最优参数,还可预测其性能。更多还原

【Abstract】 The high-range resolution profile (HRRP) represents a target’s radial backscattering intensity, which can reflect potentially discriminative information about the target’s geometry and structure. As compared to a two-dimensional or three-dimensional radar image, the HRRP is easier to generate due to the lower computational cost. As a result, the high-range resolution radar has become a leading candidate to provide all weather target recognition and battle sense.In order to acquire high-range resolution profile, radar must have the ability to process the wideband signals. There are only immature theories available of the wideband radar in the generation of wideband radar signal, target motion compensation, adaptive processing and so on. Based on the previous work, this dissertation is focused on the synthetic range profile (SRP), the temporal and space adaptive processing of the wideband radar system using synthetic wideband waveforms. Some new methods are presented, and all of which are evaluated on simulated data.In general, this dissertation is composed of the following parts:1. The research on the synthetic wideband waveform processingBased on the analysis of the characteristics of multiple synthetic wideband waveforms, a general structure model of obtaining synthetic range profile (SRP), together with a new error criterion of the SRP and a new analytical method, is established on the analysis of the characteristics of multiple synthetic wideband waveforms. At the same time, for the different synthetic wideband waveforms, their improved realization structures are proposed.2. The research on the temporal processing of the synthetic wideband waveformA general structure model of the synthetic wideband waveform’s temporal processing is established. A wideband imaging architecture based on synthetic wideband waveform and conventional Doppler filter bank structure using FFT is developed and followed by a detailed analysis of its performance. Both the theoretical analysis and simulation results show that owing to Doppler dispersion effect, the target’s SRP, with an increase in velocity, produces distortion, including range shift and shape deformation. At the same time, two related theoretical formulas are deduced for the calculation of the range shift value and evaluation of the amplitude deformation extent of a moving target’s SRP formed by the proposed imaging architecture, and thereby the maximum critical velocity is derived. When target velocity is less than the maximum critical velocity, a moving target’s SRP with acceptable amplitude distortion can be obtained.A new synthetic wideband filter bank based on the velocity bin structure is proposed, and the critical conditions of obtaining a SRP with acceptable distortion are achieved. Furthermore, the theoretical analysis results show that in order to obtain the SRP with acceptable distortion, target radial velocity must be less than the minimum subband maximum unambiguous radial velocity. Meantime, based on this proposed synthetic wideband filter bank architecture, a new method for resolving velocity ambiguity is proposed.A new synthetic wideband filter bank based on the variable PRF among subbands is proposed. By setting parameters reasonably, this new synthetic wideband filter bank architecture not only can provide a moving target’s SRP with acceptable distortion at any target velocity, but also can be implemented through a fast Fourier transform (FFT) for computational efficiency.3. The research on the space adaptive processing of the synthetic wideband signalsA general structure model of the synthetic wideband signal’s space adaptive processing is established. A wideband imaging architecture based on synthetic wideband signal and conventional adaptive processing using estimated interference-plus-noise covariance matrix is developed with a detailed analysis of its performance. The theoretical analysis and simulation results show that owing to the independent estimation of the covariance matrix in each subband, the target’s SRP produces random range sidelobes across entire range domain, which are mainly caused owing to the noise’s variance estimation varying at random from subband to subband. Two methods are proposed to relieve and eliminate the random range sidelobes. One is diagonal loading method and the other is orthogonal subspace projection method.A segment adaptive processing is proposed in order to simplify the subband adaptive processing architecture and at the same time, its performances are analyized in theory. A variable space sampling rate adaptive processing method is proposed to lower the computation complexity and its implemented method is deduced in theory.4. An efficient relative delay measurement method for digital wideband array radar with LFM waveformA relative delay measurement method for digital wideband array radar using linear frequency modulation (LFM) waveform is put forward along with a deep investigation of its basic aspects. Based on Dechirping processing technique and applying digital decimation method, the proposed measurement system can work at low processing rates, thus effectively reducing the computation and lowering hardware complexity. Moreover, by means of reasonable parameter setting and unique design construction, relative delay values among multiple digital transmit/receive (T/R) modules can be measured at one single measurement process. Their measurement accuracy is deduced in a theoretical way, while some significant factors are evaluated thereafter. It is shown that measurement error, resulting from the module thermal noise and the interaction of multiple co-existing LFM pulses respectively, consists of noise error and systematic error. Based on these analysis results, parameters of the measurement system can be optimized and its performances are predicted.更多还原