【作者】 张鹏飞；

【导师】 龚书喜；

【作者基本信息】 西安电子科技大学 ， 电磁场与微波技术， 2008， 博士

【摘要】 现代战争中,飞行器和舰船的隐身性能直接决定了它们在战场上的突防能力和战斗性能。以发动机进气道为代表的电大尺寸开口腔体结构可在飞行器鼻锥方向构成很强的后向散射,对该类结构雷达截面(RCS)的单独计算分析在隐身飞行器设计当中具有重要意义。相控阵天线已成为机载和舰载先进雷达系统的必要组成部分,对于相控阵天线辐射和散射的分析计算对于隐身舰艇的设计具有重要的指导作用。本论文密切结合“十一五”国防科技预研重点项目研究了腔体结构和阵列天线的散射分析方法和RCS控制技术。所取得的成果可概括为:1、RCS计算预处理技术研究。论文基于商业软件Rhinoceros的建模和网格剖分功能结合编写数据提取程序,完成了RCS计算中腔体和舰船的混合多边形面片建模和数据预处理,并研究了基于该模型的射线追踪、遮挡判断算法。2、腔体的RCS计算方法研究。论文分析了理想导体以及涂敷吸波材料理想导体腔体结构的IPO迭代公式。对IPO迭代算法进行了改进:首先改进了迭代计算中腔体终端的反射计算,然后将初值继承方法引入迭代过程,并利用前后向迭代、松弛因子大大加快了迭代的计算速度和收敛速度。论文采用IPO算法编程计算了进气道模型的RCS,与测试结果吻合良好。在对电大尺寸开口腔体RCS的各种算法的计算精度和计算速度分析的基础上,为保持计算精度的同时提高计算速度,论文基于消息传递协议MPI开发了腔体RCS的SBR、CRE、IPO并行计算程序,采用大粒度任务分配策略达到了较高的并行计算效率。3、腔体RCS控制技术研究。论文对涂敷吸波材料和采用S弯对腔体RCS的影响采用IPO计算程序进行了分析计算,并分析了将两种技术结合的腔体RCS控制技术。4、提出了电大尺寸载体上天线辐射场的FEM/CRE-UTD混合算法。该混合方法首先采用有限元法计算天线在自由空间的辐射场。在研究了利用富勒结构的天线辐射场复射线拟合的基础上,采用复射线展开、复射线轴线追踪、近轴近似计算技术计算载体对天线辐射场的反射,并通过UTD方法计入了棱边的绕射效应,得到电大尺寸载体上天线的辐射场。5、基于互易定理的天线模式项散射场快速计算。论文以天线的互易定理为基础,利用天线的辐射场来计算平面波照射下的天线模式项散射场。该方法可快速完成平面波在不同入射角度照射下天线模式项RCS的计算,还可以与天线辐射场的FEM/CRE-UTD混合算法相结合,分析舰载天线的天线模式项散射。6、阵列天线辐射和散射机理研究。利用阵列天线系统模型的S参数,分析了阵列天线单元的互耦。将场的矢量球面波函数展开和散射矩阵推广到阵列天线的辐射和散射分析当中,推导出阵列天线辐射和散射的基础理论公式。该公式以叠加定理的形式综合考虑了天线单元之间的互耦、馈电网络影响等因素,同时还反映了阵列天线模式散射场和天线单元辐射场的关系,公式近似后可简化为乘积定理的形式。在此基础上论文研究了大型阵列天线辐射场的近似计算方法,并采用阵列实例进行了验证。论文还采用阵列天线散射场基础理论公式的近似计算分析了阵列天线散射场的特点和峰值方向,并以一维阵列为例分离和分析了阵列天线的结构模式项和天线模式项散射,验证了理论分析结果。7、有源相控阵天线系统的辐射和散射分析。利用网络参数分析了有源相控阵天线单元的馈电系统模型,得到阵列单元的接收机负载反射系数表达式。结合阵列天线散射的基础理论公式和接收机负载反射系数表达式得到了相控阵天线的天线模式项散射近似计算公式。公式计入了单元馈电系统当中的接收机负载反射系数和移相器工作参数的影响。基于该公式,论文将天线模式项散射按照是否受配相状态影响分为两部分进行研究,最后对这样两部分散射场的特点和峰值方向进行了分析并采用微带阵列进行了验证,为相控阵天线的RCS分析计算和RCS控制提供了理论上的指导。8、舰载相控阵天线RCS控制方法研究。针对阵列天线各个散射模式,逐一分析了对应的RCS控制技术。重点分析了阵列的倾斜安装对天线辐射和散射特性的影响,对副瓣电平在天线隐身中的重要性进行了理论分析。在综合考虑辐射和散射特性的基础上利用泰勒综合和密度锥削稀疏技术设计了低副瓣电平阵列天线,并采用随机遍历算法对阵列天线副瓣进行了优化。最后研究了以控制RCS为目的的馈电系统小型化,利用左手电路原理设计了宽频带小型化电桥。更多还原

【Abstract】 The stealth character of aircraft and ships determines the penetration and combat capability of them in modern warfare. The large-scale open-ended cavities, of which the aircraft inlet is the representation, lead to a strong back scattering in the snout direction of the aircraft, which makes the computation of the Radar Cross Section (RCS) of cavity structure significant in the design of stealthy aircrafts. The phased array antenna has become an indispensable component in the advanced radar system for aircraft or naval ship. As a result, the analysis of radiation and scattering fields of the phased array antenna plays an important role in the design of stealthy naval ships. Associated with the research project, this dissertation is mainly concerned with the RCS prediction and control of the cavity structures and phased array antenna systems. The author’s major contributions are outlined as follows:1、Pretreatment for RCS computation. Modeling and meshing of the cavities and ships for RCS computation with mixed polygon facets are fulfilled by the applications of the modeling and meshing functions of the Rhinoceros software and a data extraction program. Then, based on the facet models, a study is made of the ray trace technology and shadowing judgment arithmetic.2、Study of the RCS computation algorithms for cavities. An analysis is made firstly of the Iterative Physical Optics (IPO) iterative equation for cavities of the PEC or PEC surface coated with a thin absorber layers. The IPO algorithm is improved as follows. The bottom reflection calculation in the iterative computation is improved firstly, and then, the computation and convergence speed of the IPO algorithm are improved by introducing the initial values succession into the iterative computation, and using the forward-backward iterative and the relaxation factors. The RCS of an inlet model is computed by the developed IPO program, and the results are in good agreement with the experimental ones. Based on the analysis of the precision and computation speed of the RCS computation algorithms for cavities, the dissertation develops the codes of SBR,CRE and IPO parallel algorithms by using MPI, which speeds up the computation while keeping it precise. High efficiency of the parallel algorithms is also achieved by distributing the computation task by big cells.3、The RCS control technology of cavities. The effects of the absorber materials and S-shaping on the RCS of the cavities are studied by using the IPO program. The combination of both methods in RCS control is analyzed. 4、Proposing the FEM/CRE-UTD hybrid method for the computation of the radiation fields of antennas on large carriers. The hybrid method computes the radiation fields of antennas in free space by the finite element method (FEM). After a study of the complex rays expansion of the radiation fields by use of the Fullerence mesh, the reflection effect of the carries on the fields is computed by employing the technologies of complex rays expansion (CRE) of radiation fields, ray trace and complex ray paraxial approximation. Then the diffraction effect of the edges of the carries on the fields is also taken into consideration by adopting the UTD method. As a result, the radiation fields of antennas on large carries are achieved.5、Fast computation of the antenna model scattering fields of antennas using the reciprocity theorem. The antenna model scattering fields of antennas illuminated by a plane wave are computed by using the radiation fields based on the antenna reciprocity theorem. The scattering fields of antennas illuminated by a plane wave at different incident angles can be computed quickly by this method. It can also be combined with the FEM/CRE-UTD hybrid method to compute the antenna model scattering fields of antennas on large ships.6、Study of the radiation and scattering mechanism of array antennas. The couple between the cells of array antennas is analyzed by S parameters of the model of antenna system. The basic theoretical calculation formulae for radiation and scattering of array antennas are deduced by applying spherical wave function expansion and the scattering matrix to the analysis of array antennas. In the formulae, the coupling between the cells and the reflection of the receiver load are taken into consideration, and the relationship between the antenna model scattering fields of the array and the radiation fields of cells is also shown in the formulae. The proposed formulae are still in the superposition form, which makes it possible for the formulae to be simplified to the product theorem by approximation. According to this, an approximate computation method for the radiation fields of large-scale array antennas is studied followed by its validation in the one-dimension array. The characters and peak values of scattering fields are analyzed by the approximation of the basic theoretical calculating formula. After this, the separation and analysis are made of the structural mode scattering and antenna mode scattering of a one-dimension array antennas, which validates the theoretical results.7、Analysis of the radiation and scattering of active phased-array antenna systems. The reflection coefficient of the receiver load of the cell in the array is analyzed by S parameters of the feed systems model of the active phased-array antenna. The approximation computation formula of the antenna mode scattering field is deduced by submitting the reflection coefficient of the receiver load to the basic theoretical formula, which takes the effects of the reflection coefficient of the receiver load and the parameters of the phase shifter into consideration. According to the formula, the antenna model scattering is analyzed by dividing it into two parts. And their characters and the max direction are analyzed and testified in the one-dimension array antenna, which plays a guidance role in the computation of the scattering fields of the phased array and its RCS control.8、RCS control of the phased array antenna on naval ships. Analysis is made of the RCS control technologies for different scattering models of the array antennas. Emphasis is put on the analysis of the effects of array leaning on its radiation and scattering characters, which shows that the side lobe plays an important role in the stealth characters of the array. The array antenna with low side lobe is designed by employing the Taylor synthesis and density taper sparseness with an overall consideration of the radiation and scattering performance. The side lobe of the array antenna is optimized by random search. Finally, a discussion is made about the compact feed system used in the RCS control of array antennas. And based on the left-hand circuit, a compact enhanced-bandwidth hybrid ring is designed.更多还原