反射面型脉冲辐射天线的快速优化方法研究

发布时间：2018-03-28 03:30

本文选题：反射面型脉冲辐射天线　切入点：共形时域有限差分法　出处：《西南交通大学》2014年博士论文

【摘要】：反射面型脉冲辐射天线能很好地定向辐射电磁脉冲,它具有主瓣波束窄,作用距离远,空间、时间分辨率高等优点,在定向能武器、目标探测、成像等领域都有着广泛的应用。由于反射面型脉冲辐射天线所辐射的电磁脉冲其频谱成分丰富,作为馈源的超宽带天线将无法拥有固定的相位中心,这是反射面型脉冲辐射天线设计中的一大难点。为了使反射面型脉冲辐射天线能向远场辐射高峰值、高保真度的冲击脉冲,提高馈源的能量辐射效率,通常依赖数值仿真方法和优化算法对反射而型脉冲辐射天线进行优化设计。然而,该类天线为电大尺寸天线,反复数值模拟计算,将占用大量计算资源,优化速度缓慢。因此,本文致力于寻求加快反射面型脉冲辐射天线优化设计速度的普适方法。时域电磁场计算方法可较为直接、直观地求解超宽谱电磁脉冲问题。其中,共形时域有限差分法(Conformal Finite Difference Time Domain, CFDTD)在处理带有曲面结构的电磁目标仿真问题时,具有独特的优势,适合于反射面型脉冲辐射天线的研究。但是,由于仿真目标形式多样,它们的共形网格建模往往十分繁琐。为此,本文将研究满足三维CFDTD方法求解的电磁目标自动几何建模方法。同时,优化算法已经普遍应用于各类天线的优化设计之中。在优化过程中,反复调用计算天线参数的正问题的仿真程序是优化设计中最为耗时且占用计算资源的。为此,本文引入代理模型,研究减少调用数值仿真程序次数的全局优化算法,以减少天线的优化设计时间,提高优化效率。综上所述,本文主要工作如下：第一,基于“切片-线扫描”法,实现多材料复杂实体组合的共形网格自动建模,适用于CFDTD求解,具备很好的通用性。该方法以三角面元文件为输入数据,通过对“切片-线扫描”法的改进,以及对网格相对面积的修正,可以快速确定各网格棱边和面上的等效实体信息,实现目标模型的高效共形网格重构。将该方法应用于一个对开口渐变曲线较为敏感的对跖式渐变开槽天线的几何建模,其数值模拟结果与测试结果吻合很好,表明该共形网格自动剖分方法的正确性和有效性。第二,研究了Taguchi优化方法与BP (Back Propagation)神经网络相结合的方法,称作BP-based Taguchi算法。通过函数测试,分析优化维数增加,以及优化进程的推进,对BP神经网络预测误差的影响,认为,有必要在BP神经网络使用一定代数后,重新训练BP神经网络,以确保BP神经网络的预测精度满足进一步的寻优要求。分别对三元非规则三角天线阵(3维)、十元非规则三角天线阵(6维)、四元非规则矩形边界天线阵(8维)和圆弧式变形TEM喇叭天线单元(13维)进行了优化。优化结果表明,当优化维数低于8维时,相较于Taguchi优化方法,采用BP-based Taguchi算法可有效减少调用数值仿真程序的次数。第三,实现了基于混合代理模型的高效全局优化算法(Hybrid-Surrogate-Model-based Efficient Global Optimization Algorithm, HSM-based EGO)。 HSM-based EGO算法以Kriging模型和RBF (Radial Basis Function)神经网络为混合代理模型,分别根据最大期望改进、最低抽样密度和当前局部最优来获取新抽样点,每代只需调用数值仿真程序3次,且与优化维数无关。将HSM-based EGO算法应用于一个12维的复合振子天线优化设计,并与EGO算法和微分进化策略(Differential Evolution Strategy, DES)算法的优化结果进行了对比,它们的收敛曲线表明了这种采用混合代理模型的优化算法不仅具有较快的收敛速度,也有良好的全局搜索能力,适用于高维优化问题的全局寻优。第四,当馈源已确定,且为对称结构时,本文根据反射面型脉冲辐射天线的基本特性,提出了以馈源轴向辐射脉冲的峰值时刻瞬态方向图为参考,以确定超宽带馈源时域近似辐射中心与辐照角的方法,从而实现反射面型脉冲辐射天线的快速设计,使反射面天线系统在轴向的辐射增益最强。将该设计方法分别应用于前馈式反射面型脉冲辐射天线(以阻抗渐变式变形TEM喇叭为馈源)、卡塞格伦型脉冲辐射天线(以圆弧式变形TEM喇叭为馈源)和单偏置反射面型脉冲辐射天线(以2×2同轴指数渐变式变形TEM喇叭天线阵为馈源)的快速设计,并将它们的设计结果与采用扫参或优化算法优化设计的结果进行对比,各方法的设计结果皆非常接近,表明了这种时域快速设计方法的有效性。第五,本文利用带椭球反射面的近场聚焦天线具有天然近似辐射中心的结构特点,设计了一款远场辐射性能良好的准格里高利型脉冲辐射天线。以脉冲宽度分别为200ps和330ps的高斯脉冲激励该天线,该天线馈源的瞬时辐照角宽度符合理论设计要求,当抛物反射面口面直径为1.5m时,天线对应的3dB波束宽度皆小于±3°(H面)和±5°(E面),表明该天线适合于亚纳秒级电磁脉冲的辐射,且具有良好的定向性。
[Abstract]:Reflective pulse radiation antenna can well directional radiation of electromagnetic pulse, it has narrow beam main lobe, the role of distance, space time, high resolution, energy weapons, in the direction of target detection, imaging and other fields are widely used. Because the reflective pulse radiation antenna radiation of the electromagnetic spectrum rich composition as the pulse ultra wideband antenna phase center will not have fixed, this is one of the difficulties of reflective pulse radiation antenna design. In order to make reflective pulse radiation antenna to the far field radiation peak value, high fidelity impulse, improve the energy radiation efficiency of the feed and often rely on the method of numerical simulation and optimization algorithm for reflection type pulse radiation antenna is optimized. However, this kind of antenna is electrically large antenna, repeated numerical simulation, will occupy a large amount of computing resources, and The speed is slow. Therefore, this paper is devoted to seeking to speed up the reflective pulse radiation antenna optimization design speed universal method. The time-domain method can be more direct and intuitive solution of ultra wide spectrum electromagnetic pulse. The conformal FDTD method (Conformal Finite Difference Time Domain, CFDTD) in the problem of electromagnetic target simulation with curved structure, has unique advantages, suitable for the study of pulse radiation antenna on the reflection plane. However, the simulation of target forms, their conformal mesh modeling are often very complicated. Therefore, this paper will study the target to meet the electromagnetic automatic modeling method for solving the three-dimensional CFDTD method. At the same time, optimization the algorithm has been widely used in various types of antennas. In the optimization process, the simulation program is called repeated calculation of the antenna parameters are optimized. In the most time-consuming and consumes computing resources. Therefore, this paper introduces the proxy model to reduce the global optimization of numerical simulation program the number of calls, time optimization design to reduce the antenna, improve the optimization efficiency. To sum up, the main work is as follows: first, "cut line scanning method based on multi material complex conformal mesh modeling combinations, suitable for the solution of CFDTD, has good versatility. This method takes the triangular element file as input data, through the improvement of the" cut line scanning method, and modified the relative area of the grid, can quickly determine the grid edge and on the surface of the equivalent the entity information, to achieve the goal of model, conformal mesh reconstruction. This method is applied to a more sensitive to the gradient curve of plantar opening type tapered slot antenna geometric modeling, the numerical simulation results and The test results are in good agreement, show the correctness and effectiveness of the conformal mesh generation method. Second, research on Taguchi optimization method and the BP (Back Propagation) method combined with neural network, called BP-based Taguchi algorithm. Through the function test, analysis and optimization of dimension increase, and promote the optimization of the process, think the BP neural network prediction error, and it is necessary to use some algebra in BP neural network, to train the BP neural network, to ensure that the prediction accuracy of BP neural network to meet the requirements of further optimization of three yuan respectively. The irregular triangular array (3 dimension), ten yuan (non regular triangle array 6 dimension), four yuan of irregular rectangle array (8 dimension) and arc deformation of TEM horn antenna unit (13 dimension) is optimized. The optimization results show that when the optimal dimension less than 8 dimensions when compared to the Taguchi optimization method, using BP-based The Taguchi algorithm can effectively reduce the number of calls to the numerical simulation program. Third, to achieve an efficient global optimization algorithm based on hybrid agent model (Hybrid-Surrogate-Model-based Efficient Global Optimization Algorithm, HSM-based EGO). HSM-based EGO algorithm based on the Kriging model and the RBF (Radial Basis Function) neural network mixed agent model, respectively according to the maximum expected improvement, minimum sampling the current density and the local optimum to obtain new sampling points, each generation can only call a numerical simulation program for 3 times, and has nothing to do with the optimal dimension. HSM-based EGO algorithm is applied to a 12 dimensional composite oscillator antenna design and optimization, and EGO algorithm and differential evolution strategy (Differential Evolution, Strategy, DES) algorithm optimization the results were compared and their convergence curves show that the hybrid optimization algorithm model not only has Fast convergence speed, also has good global search capability, suitable for high dimensional global optimization problem. Fourth, when the feed has been determined, and the symmetrical structure, according to the basic characteristics of reflective pulse radiation antenna, put forward to the peak time of transient axial direction feed radiation pulse figure for reference. To determine the ultra wideband feed time domain approximation method for radiation center and irradiation angle, so as to realize the rapid design of reflective pulse radiation antenna, the reflector antenna in the strongest radiation gain axial. The design methods are applied to feedforward reflective pulse radiation antenna (with the impedance tapered TEM horn feed for deformation). Casey Glenn type pulse radiation antenna (with arc type TEM horn feed for deformation) and single offset reflective pulse radiation antenna (2 x 2 coaxial progressive deformation index TEM horn antenna array For the fast feed) design, and the design results and they used to sweep or optimization algorithm to optimize the design by comparing the results of each method design results are very close to show the effectiveness of the fast design method of the time domain. Fifth, the structure with reflecting surface ellipsoid near field focusing antenna has a natural approximation the radiation center, designed a good performance of the quasi far field radiation Gregory type pulse radiation antenna. The pulse width was 200ps and 330ps excitation of the antenna Gauss pulse, the transient radiation antenna angle width meets the requirements of theoretical design, when the parabolic reflector aperture diameter is 1.5m, the 3dB beam width of antenna the corresponding is less than 3 degree (H) and + 5 degrees (E surface), show that the antenna is suitable for sub nanosecond pulsed electromagnetic radiation, and has good directivity.

【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN820

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