【作者】 何密；

【导师】 肖顺平；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2012， 博士

【摘要】 极化信息的充分利用可以显著提高雷达在杂波抑制、目标检测、目标分类识别与抗干扰等方面的性能,而目标极化特性的准确获取是雷达目标分类识别、杂波抑制和抗干扰的基础和前提条件,具有重要的理论和现实意义。论文以防空反导和气象目标探测为应用背景,立足于同时极化测量雷达体制,紧密围绕如何准确获取目标极化散射特性这一主线,深入开展了多极化通道测量波形非正交性抑制、目标运动调制误差补偿、雷达系统误差无源和有源极化校准以及极化雷达杂波抑制方法等方面的研究,主要内容如下：针对同时极化测量体制雷达,研究了由于多极化通道测量波形非理想正交以及目标运动引入的目标极化散射矩阵(Polarization Scattering Matrix, PSM)测量误差的修正问题。定义了距离-速度-加速度联合模糊函数矩阵,定量刻画了速度和加速度对正负斜率线性调频极化测量雷达各极化通道隔离度的影响；分析了调频连续波全极化雷达去斜处理获取PSM时的交叉极化通道干扰,提出了基于分数阶傅里叶变换的交叉通道干扰抑制方法,与传统的方法相比,该方法获得的距离像具有更低的峰值旁瓣电平和积累旁瓣电平,可显著提高多目标极化测量时的弱目标极化测量性能和单目标极化测量时较弱散射矩阵元素的测量性能；分析了目标运动状态对全极化雷达PSM测量精度的影响,针对匹配滤波和去斜处理两种极化测量方法,提出基于分数阶傅里叶变换的运动参数估计和补偿方法,仿真实验表明,该方法较常规方法具有更高的精度。研究了全极化雷达的无源极化校准技术。建立了全极化雷达PSM测量系统误差模型,分析了几种典型点目标无源极化校准算法在不同天线极化隔离度下性能的优劣,发现了传统无源校准算法在实际应用中的不足,提出了一种基于Pauli基分解的极化校准算法,该方法通过选择任意三个PSM互相正交的目标作为定标体实现全极化雷达的校准,放宽了传统校准方法对定标体PSM的苛刻需求。基于荷兰Delft理工大学的PARS AX (Polarimetric Agile Radar S-And X-band)极化气象雷达外场校准实验结果验证了所提算法的有效性,校准后PSM的最大幅度相对误差为-22.04dB、最大相位误差为1.40°。针对大口径天线雷达极化校准这一理论和工程现实难题,研究了基于极化有源校准器(Polarimetric Active Radar Calibrator, PARC)的动态极化校准方法,设计了基于数字射频存储器的双/单天线PARC系统,据此提出了频域动态极化校准方法,通过匀速旋转PARC天线实现待校准极化雷达的接收信号调制,在频域上求解全极化雷达系统误差模型中的未知量。该方法克服了传统静态极化校准方案中多次测量引入的误差和PARC天线初始角度的影响。仿真实验表明,基于PARC的动态极化校准算法性能优于TSC (Target Spinor Calibration)和FPCT (Full Polarimetric Calibration Technique)等传统静态极化校准算法。研究了气象目标极化特性测量中的杂波抑制技术,提出一种基于数学形态学和双SLDRs (Spectral Linear Depolarization Ratios)滤波器的极化杂波抑制方法。该方法在对气象目标、地杂波的双距离-多普勒谱去极化比统计分析基础上,利用数学形态学算子构造了二值掩模矩阵并据此对气象目标的距离-多普勒谱进行滤波。结合PARSAX极化雷达同时极化测量采集的气象目标数据,对极化杂波抑制后气象目标的反射率、平均多普勒速度和多普勒宽度的计算结果分析表明了所提方法的有效性。通过与传统方法实验结果的对比,验证了所提方法的优越性。论文的研究成果有助于推动极化雷达技术的应用,对于提高防空反导、气象观测、对地侦察等应用领域中的目标分类识别、杂波抑制和抗干扰等的性能具有重要意义。更多还原

【Abstract】 The adequate use of polarization information can remarkably improve theperformance of radar in the aspect of clutter suppression, target detection, targetidentification and recognition, and anti-jamming, etc. Therefore, the accurateacquirement of targets’ polarimetric characteristics, which is a basis and preconditionfor target identification and recognition, clutter suppression, and anti-jamming of radar,owns an important meaning in theory and practice. Under the background of airsurveillance, missile defence, and weather target exploration, this paper, closesurrounding the main line of how to precisely obtain targets’ polarimetric scatteringcharacteristics, deeply studies on the methods of the measurement-waveformnon-orthogonality suppression, the kinematic error compensation, the passive and activecalibration of polarimetric radar system error and the polarimetric-radar cluttersuppression, etc., based on the simultaneous measurement scheme. The main contentsof the dissertation are as follows:For the simultaneous measurement polarimetric radar, the modification of errorsdue to the unideal orthogonality of measurement waveforms and target kinesi in themulti-polarimetric channels during the measurement of the polarization scatteringmatrix (PSM) is studied. The effect of the velocity and acceleration on the waveformisolation of the opposite slope linear frequency modulated signals is quantitativelydescribed by defining the range-velocity-acceleration ambiguity function matrix. Afterthe cross-channel interference produced by the frequency-modulated continuous-wavefull-polarimetric radar using the de-ramping processing to obtain the PSM is analyzed,the interference suppression method based on the fractional Fourier transform isproposed. Compared with the traditional method, the proposed method can achievelower peak sidelobe levels and integrated sidelobe levels in range profiles, which canobviously improve the polarimetric measurement performance of weak targets formulti-targets and weak polarimetric scattering components for a single target. After theerror due to the target kinestate is analyzed for the full-polarimetric radar during thePSM measurement, the estimation and compensation method of the kinetic parametersbased on the fractional Fourier transform is proposed. The simulative results show thatthe accuracy of the proposed method is higher than the conventional method.The point-target passive polarimetric calibration technique is studied. Afull-polarimetric radar system error model during PSM measurement is established. Thepolarimetric calibration performances of several typical point-target passivepolarimetric calibration algorithms are compared under different antenna polarizationisolations. After the disadvantage of the traditional passive calibration algorithms in thepractical application is founded, a new polarimetric calibration algorithm based on the Pauli-basis decomposition is proposed. Any three targets satisfying the orthogonalcondition can be chosen as calibrators to calibrate the full-polarimetric radar, whichbroaden the limitation to PSM of calibrators in the traditional calibration algorithms.The validity of the proposed method is proved by the out-field calibration experimentalresult of the PARSAX (Polarimetric Agile Radar S-And X-band) polarimetric weatherradar developed by the Delft University of Technology in the Netherlands. After theexternal calibration, the maximum amplitude and phase relative errors of the relativePSM are-22.04dB and1.40°, respectively.For the polarimetric calibration with the theory and practical engineering problemof the giant aperture antenna radar, the dynamic polarimetric calibration algorithmbased on the digital polarimetric active radar calibrator (PARC) is studied. The newPARC systems with two antennas and a single antenna are designed based on the digitalradio frequency memory, respectively. The frequency-domain dynamic polarimetriccalibration algorithm is proposed by the uniform-speed rotation of the PARCs’ antennasto modulate receive signals of the polarimetric radar. The unknowns in the system errormodel of the full-polarimetric radar are resolved in the frequency domain. The proposedmethod can eliminate the errors due to a set of measurements and the initial angles ofPARCs’ antennas in the traditional static calibration methods. The simulative resultsshows that the calibration performance of the dynamic polarimetric calibrationalgorithm based on the digital PARC is better than the traditional static polarimetriccalibration algorithms, such as the Target Spinor Calibration (TSC) and the FullPolarimetric Calibration Technique (FPCT), etc.The clutter suppression technique for the polarimetric characteristic measurementof atmospheric targets is studied. A new polarimetric clutter suppression method basedon the mathematical morphology method and double spectral linear depolarizationratios (SLDRs) is proposed. A binary mask matrix is constructed by using mathematicalmorphology operators via the analysis of statistical properties of the doublerange-Doppler spectral linear depolarization ratios of atmospheric targets and theground clutter. Using the atmospheric target data acquired by the PARSAX polarimetricradar in the simultaneous measurement mode, the analysis of calculation results of theatmospheric target data after clutter suppression in the range-Doppler spectrogram, thereflectivity, the mean Doppler velocity, and the Doppler width show the efficiency ofthe proposed method. Compared with the results of the traditional method, results of theproposed method verify its improvement and advantage.The research results of this dissertation help to promote the application of thepolarimetric radar technology and possess an important meaning to improve theperformance of target identification and recognition, clutter suppression andanti-jamming in the application area of the air surveillance, missile defence, weatherobservation and ground reconnaissance.更多还原