本文選題：反射面型脈沖輻射天線　切入點(diǎn)：共形時(shí)域有限差分法　出處：《西南交通大學(xué)》2014年博士論文

【摘要】：反射面型脈沖輻射天線能很好地定向輻射電磁脈沖,它具有主瓣波束窄,作用距離遠(yuǎn),空間、時(shí)間分辨率高等優(yōu)點(diǎn),在定向能武器、目標(biāo)探測(cè)、成像等領(lǐng)域都有著廣泛的應(yīng)用。由于反射面型脈沖輻射天線所輻射的電磁脈沖其頻譜成分豐富,作為饋源的超寬帶天線將無(wú)法擁有固定的相位中心,這是反射面型脈沖輻射天線設(shè)計(jì)中的一大難點(diǎn)。為了使反射面型脈沖輻射天線能向遠(yuǎn)場(chǎng)輻射高峰值、高保真度的沖擊脈沖,提高饋源的能量輻射效率,通常依賴數(shù)值仿真方法和優(yōu)化算法對(duì)反射而型脈沖輻射天線進(jìn)行優(yōu)化設(shè)計(jì)。然而,該類天線為電大尺寸天線,反復(fù)數(shù)值模擬計(jì)算,將占用大量計(jì)算資源,優(yōu)化速度緩慢。因此,本文致力于尋求加快反射面型脈沖輻射天線優(yōu)化設(shè)計(jì)速度的普適方法。時(shí)域電磁場(chǎng)計(jì)算方法可較為直接、直觀地求解超寬譜電磁脈沖問(wèn)題。其中,共形時(shí)域有限差分法(Conformal Finite Difference Time Domain, CFDTD)在處理帶有曲面結(jié)構(gòu)的電磁目標(biāo)仿真問(wèn)題時(shí),具有獨(dú)特的優(yōu)勢(shì),適合于反射面型脈沖輻射天線的研究。但是,由于仿真目標(biāo)形式多樣,它們的共形網(wǎng)格建模往往十分繁瑣。為此,本文將研究滿足三維CFDTD方法求解的電磁目標(biāo)自動(dòng)幾何建模方法。同時(shí),優(yōu)化算法已經(jīng)普遍應(yīng)用于各類天線的優(yōu)化設(shè)計(jì)之中。在優(yōu)化過(guò)程中,反復(fù)調(diào)用計(jì)算天線參數(shù)的正問(wèn)題的仿真程序是優(yōu)化設(shè)計(jì)中最為耗時(shí)且占用計(jì)算資源的。為此,本文引入代理模型,研究減少調(diào)用數(shù)值仿真程序次數(shù)的全局優(yōu)化算法,以減少天線的優(yōu)化設(shè)計(jì)時(shí)間,提高優(yōu)化效率。綜上所述,本文主要工作如下：第一,基于“切片-線掃描”法,實(shí)現(xiàn)多材料復(fù)雜實(shí)體組合的共形網(wǎng)格自動(dòng)建模,適用于CFDTD求解,具備很好的通用性。該方法以三角面元文件為輸入數(shù)據(jù),通過(guò)對(duì)“切片-線掃描”法的改進(jìn),以及對(duì)網(wǎng)格相對(duì)面積的修正,可以快速確定各網(wǎng)格棱邊和面上的等效實(shí)體信息,實(shí)現(xiàn)目標(biāo)模型的高效共形網(wǎng)格重構(gòu)。將該方法應(yīng)用于一個(gè)對(duì)開口漸變曲線較為敏感的對(duì)跖式漸變開槽天線的幾何建模,其數(shù)值模擬結(jié)果與測(cè)試結(jié)果吻合很好,表明該共形網(wǎng)格自動(dòng)剖分方法的正確性和有效性。第二,研究了Taguchi優(yōu)化方法與BP (Back Propagation)神經(jīng)網(wǎng)絡(luò)相結(jié)合的方法,稱作BP-based Taguchi算法。通過(guò)函數(shù)測(cè)試,分析優(yōu)化維數(shù)增加,以及優(yōu)化進(jìn)程的推進(jìn),對(duì)BP神經(jīng)網(wǎng)絡(luò)預(yù)測(cè)誤差的影響,認(rèn)為,有必要在BP神經(jīng)網(wǎng)絡(luò)使用一定代數(shù)后,重新訓(xùn)練BP神經(jīng)網(wǎng)絡(luò),以確保BP神經(jīng)網(wǎng)絡(luò)的預(yù)測(cè)精度滿足進(jìn)一步的尋優(yōu)要求。分別對(duì)三元非規(guī)則三角天線陣(3維)、十元非規(guī)則三角天線陣(6維)、四元非規(guī)則矩形邊界天線陣(8維)和圓弧式變形TEM喇叭天線單元(13維)進(jìn)行了優(yōu)化。優(yōu)化結(jié)果表明,當(dāng)優(yōu)化維數(shù)低于8維時(shí),相較于Taguchi優(yōu)化方法,采用BP-based Taguchi算法可有效減少調(diào)用數(shù)值仿真程序的次數(shù)。第三,實(shí)現(xiàn)了基于混合代理模型的高效全局優(yōu)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)神經(jīng)網(wǎng)絡(luò)為混合代理模型,分別根據(jù)最大期望改進(jìn)、最低抽樣密度和當(dāng)前局部最優(yōu)來(lái)獲取新抽樣點(diǎn),每代只需調(diào)用數(shù)值仿真程序3次,且與優(yōu)化維數(shù)無(wú)關(guān)。將HSM-based EGO算法應(yīng)用于一個(gè)12維的復(fù)合振子天線優(yōu)化設(shè)計(jì),并與EGO算法和微分進(jìn)化策略(Differential Evolution Strategy, DES)算法的優(yōu)化結(jié)果進(jìn)行了對(duì)比,它們的收斂曲線表明了這種采用混合代理模型的優(yōu)化算法不僅具有較快的收斂速度,也有良好的全局搜索能力,適用于高維優(yōu)化問(wèn)題的全局尋優(yōu)。第四,當(dāng)饋源已確定,且為對(duì)稱結(jié)構(gòu)時(shí),本文根據(jù)反射面型脈沖輻射天線的基本特性,提出了以饋源軸向輻射脈沖的峰值時(shí)刻瞬態(tài)方向圖為參考,以確定超寬帶饋源時(shí)域近似輻射中心與輻照角的方法,從而實(shí)現(xiàn)反射面型脈沖輻射天線的快速設(shè)計(jì),使反射面天線系統(tǒng)在軸向的輻射增益最強(qiáng)。將該設(shè)計(jì)方法分別應(yīng)用于前饋式反射面型脈沖輻射天線(以阻抗?jié)u變式變形TEM喇叭為饋源)、卡塞格倫型脈沖輻射天線(以圓弧式變形TEM喇叭為饋源)和單偏置反射面型脈沖輻射天線(以2×2同軸指數(shù)漸變式變形TEM喇叭天線陣為饋源)的快速設(shè)計(jì),并將它們的設(shè)計(jì)結(jié)果與采用掃參或優(yōu)化算法優(yōu)化設(shè)計(jì)的結(jié)果進(jìn)行對(duì)比,各方法的設(shè)計(jì)結(jié)果皆非常接近,表明了這種時(shí)域快速設(shè)計(jì)方法的有效性。第五,本文利用帶橢球反射面的近場(chǎng)聚焦天線具有天然近似輻射中心的結(jié)構(gòu)特點(diǎn),設(shè)計(jì)了一款遠(yuǎn)場(chǎng)輻射性能良好的準(zhǔn)格里高利型脈沖輻射天線。以脈沖寬度分別為200ps和330ps的高斯脈沖激勵(lì)該天線,該天線饋源的瞬時(shí)輻照角寬度符合理論設(shè)計(jì)要求,當(dāng)拋物反射面口面直徑為1.5m時(shí),天線對(duì)應(yīng)的3dB波束寬度皆小于±3°(H面)和±5°(E面),表明該天線適合于亞納秒級(jí)電磁脈沖的輻射,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.

【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN820

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本文編號(hào)：1674588