【作者】 王岩；

【导师】 祁嘉然；

【作者基本信息】 哈尔滨工业大学 ， 电子与通信工程（专业学位）， 2018， 硕士

【摘要】 近年来,喇叭天线越来越多的被应用于卫星通信领域,其原因是其具有很高的通信稳定性、较低的插入损耗和能承载较大的功率容量。传统的波纹喇叭结构上比较单一,口面场具有比较规则的结构,这样的天线结构具有比较简单的辐射场表达式。但是对于复杂的天线结构,往往难以直接设计其结构,需要通过一些数值的计算方法设计其结构。目前来看,通信技术已经发展的很成熟,那些传统的天线设计模型远远不能满足现代通信所需要,这样,人们提出了借助于数值计算的技术来设计和优化天线结构,这样可以更高效的实现目标。本文通过对军民领域日益需求强烈的卫星通行系统做了详细分析,并结合现代天线的应用背景和理论分析,提出了一套新型的数值设计和优化天线的解决方法。包括常见的不均匀波导结、同轴结构和混合波导结构的详细分析、理论建模和数值计算,得出其天线内部的传输损耗、阻抗特性和辐射特性。提高了设计的精度和速度。本文首先介绍了各个坐标系下各种电磁场分量表达式的由来,由此引出金属腔体内部波导不连续结构的模式匹配法,并且通过严格的数学推导,得出各个不连续波导结中本征模式互耦系数矩阵。把一个现实的天线结构等效为一个多模电路模型,从而利用算法可以设计和优化。然后介绍了金属波导端口的数值计算方法。球面波展开法是一种常见计算波导口面的计算方法。通过模式匹配法获得金属导体内部的S参数,然后通过球面波展开法求出天线辐射口面的S参数,这样便得出该天线的完整S参数。当天线的馈源端口模式确定时,便可以得出整个空间任意一个位置的电磁波辐射场量。端口间的隔离度、各个端口的反射系数也可以随之算出。本文为了验证该数值算法的准确性,设计了两种可以用数值算法设计其结构的Ku/Ka波段双频馈源天线,提出了一种新型介质加载的双频馈源天线,以保证其良好的辐射特性。该馈源天线主要用于卫星通信地面站反射面天线的馈源。其结构尺寸受到严格的大小限制,这样可以有效地提高辐射效率。两种馈源天线都可以达到良好的端口反射系数、较低的交叉极化电平、较稳定的相位中心和理想的旋转对称方向图。原理是利用模式匹配法把需要设计的喇叭构建成一个理想的数学模型。其中,很多结构参数需要优化。这样,其理想数学模型便成为了一个多目标函数,再结合遗传算法给出初值,进行迭代,设置迭代次数、截止频率、需要考虑的模式数目等等,通过MATLAB运行,直至优化目标结果收敛。最后得出的数据为该天线的优化结果。通过与HFSS、CST等全波仿真软件进行对比,可以验证该算法的极高的运算效率和较高的数值准确度。该方法有一定的通用性,可以针对一些旋转对称的结构进行设计和优化。另外,也可以针对介质杆加载的结构进行分析。主要是针对一个复杂结构的馈源喇叭系统,可以有效的建立数学模型,实现多目标多模式的系统优化。可以保证足够的精度。体现了数值计算的高效性。本文最后为解决传统的全波仿真技术在设计和优化多个指标的效率低下的问题,系统的提出了一套完整的优化设计算法,并在一些常用的实际背景下应用。虽然该算法在设计和优化上有一些结构的局限性,但是相信在不远的将来,能不断地完善,运用数学计算优化天线喇叭是目前的一种趋势,日趋成熟的算法优化体系将大大缩短项目进程。更多还原

【Abstract】 In recent years,more and more horn antennas have been used in the field of satellite communications because of their high communication stability,low insertion loss,and ability to carry large power capacity.The traditional corrugated horn structure is relatively simple,and the mouth-surface field has a relatively regular structure.Such an antenna structure has a relatively simple radiation field expression.However,for a complex antenna structure,it is often difficult to design its structure directly,and its structure needs to be designed through some numerical calculation methods.At present,communication technology has developed very well.Those traditional antenna design models are far from meeting the needs of modern communications.In this way,people have proposed the use of numerical calculation techniques to design and optimize the antenna structure,which can be more efficient..This paper makes a detailed analysis of satellite traffic systems that are increasingly in demand in the military and civilian areas.Combined with the application background and theoretical analysis of modern antennas,this paper proposes a new set of numerical methods for designing and optimizing antennas.Including the detailed analysis of common non-uniform waveguide junctions,coaxial structures and hybrid waveguide structures,theoretical modeling and numerical calculations,the internal transmission losses,impedance characteristics and radiation characteristics of the antenna are obtained.Improve the accuracy and speed of the design.This paper first introduces the origins of various electromagnetic field component expressions in each coordinate system,which leads to a pattern matching method for the discontinuous structure of the waveguide inside the metal cavity.Through rigorous mathematical derivation,the intrinsic characteristics of each discrete waveguide junction are obtained.Pattern mutual coupling coefficient matrix.A realistic antenna structure is equivalent to a multimode circuit model so that an algorithm can be used to design and optimize.This paper introduces the numerical calculation method of the metal waveguide port.The spherical wave expansion method is a common calculation method for the waveguide surface.The S-parameter inside the metal conductor is obtained by the pattern matching method,and then the S-parameter of the antenna radiation surface is obtained by the spherical wave expansion method,so that the complete S-parameter of the antenna is obtained.When the mode of the feed port of the antenna is determined,the amount of electromagnetic radiation at any position in the entire space can be obtained.The isolation between ports and the reflection coefficient of each port can also be calculated accordingly.In order to verify the accuracy of the numerical algorithm,two Ku/Ka-band dual-frequency feed antennas that can be designed using numerical algorithms are designed,and a new type of medium-loaded dual-frequency feed antenna is proposed to ensure its goodness.The radiation characteristics.The feed antenna is mainly used for the feed of the reflector antenna of the satellite ground station.The size of its structure is strictly limited,which can effectively improve the radiation efficiency.Both feed antennas can achieve good port reflection coefficients,low crosspolarization levels,relatively stable phase centers,and ideal rotational symmetry patterns.The principle is to make use of the pattern matching method to construct the horn that needs to be designed into an ideal mathematical model.Among them,many structural parameters need to be optimized.In this way,its ideal mathematical model has become a multi-objective function,combined with the genetic algorithm to give initial values,iterates,set the number of iterations,cutoff frequency,the number of models to be considered,etc.,run through MATLAB,until the optimization of the target results convergence.The resulting data is the optimized result of the antenna.Comparing with full-wave simulation software such as HFSS and CST,it can verify the algorithm’s extremely high calculation efficiency and high numerical accuracy.This method has certain versatility and can be designed and optimized for some rotationally symmetric structures.In addition,the analysis of the structure loaded by the dielectric rod can also be performed.Mainly for a complex structure of the feed horn system,can effectively establish a mathematical model to achieve multi-objective and multimode system optimization.Sufficient accuracy can be guaranteed.Embodies the high efficiency of numerical calculations.At the end of this paper,in order to solve the inefficiency of traditional full-wave simulation technology in designing and optimizing multiple indexes,a complete optimization design algorithm is proposed systematically and applied in some common practical contexts.更多还原