GPSAR 平面螺旋天线群延迟特性分析

在地表穿透合成孔径雷达工作过程中,为了利用平面螺旋天线进行成像,必须对影响成像质量的色散问题进行 补偿。文中对阿基米德平面螺旋天线的固有延迟特性进行了分析,并根据自身几何结构特性推导出了该天线固有群延迟 的估计公式。计算结果与测试结果基本一致验证了天线固有群延迟估计的可行性和有效性。     

螺旋天线的快速分析及宽带化设计

研究了一种快速计算螺旋天线电特性的新方法,并结合遗传算法对天线进行了宽带、小型化设计。采用直线段对法向模螺旋天线进行划分,应用合成基函数及合成检验函数的矩量法对阻抗矩阵进行了降阶处理,节省了求解矩阵方程所需的时间和存储量。结合遗传算法对加载法向模螺旋天线上的加载集总元件的值、加载位置以及匹配网络参数进行一体化优化设计,并采用Sherman-Morrison-Woodbury公式快速求解加载后的矩阵方程,提高了优化设计的效率。最后,成功设计了一副工作在100～1000MHz的宽带小型化螺旋天线。     

基模螺旋天线的研究

本文提出了一种计算基模螺旋天线的新方法.该方法采用螺旋线段对基模螺旋天线进行划分,只需少量分段就可用矩量法对其进行精确模拟分析.文中求出了螺旋天线上的电流分布和远场方向图,与直线段模拟计算结果吻合良好.求阻抗矩阵 Z时,利用螺旋天线的对称性和周期性,只需求出一小部分元素就可得到Z 矩阵的其它元素的值.该方法分段数少,使得计算时间和计算所需存储量大大减小,计算速度和精度显著提高.     

探针馈电印刷线天线的矩量法分析——（Ⅰ）单臂天线

利用同轴内导体延和为探针对印刷天线进行直接馈电是一种易于实现的馈电方式。本文介绍了一种分析单臂探针馈电印刷线天线的数值方法,该方法是基于并矢格林函数和互易定量求解电流积分方程的矩量法,适合于分析任意形状印刷线天线,首先给出描述电流分布的积分方程及其矩量法求解公式,在解得电流分布基础上,应用驻相法计算远区辐射场,通过计算与实验比较,验证了分析方法和计算程序的正确性,最后对一圆极化开口印刷圆环天线进行分析计算,表明了方法的实用价值。     

探针馈电印刷线天线的矩量法分析——（Ⅱ）多臂天线

通过应用模式分解法,本文将单臂探针馈电印刷线天线的分析方法推广到具有旋转对称性的任意多臂探针馈电印刷线天线的分析计算。首先给出探针馈电N臂印刷线天线的电流积分方程、矩量方程及远区辐射场计算公式;通过一个中心馈电螺旋天线的分析计算验证方法和计算程序的正确性;设计出具有良好圆极化特性的开口双圆环印刷线天线;最后分析了一探针馈电四臂印刷螺旋天线的辐射特性。     

小型超宽带平面天线阵列设计与优化

提出了一种小型超宽带(UWB)平面天线阵列并进行了优化.首先设计了两个不同的UWB天线单元方案:印刷天线-Vivaldi天线、平板天线-平面螺旋天线,并通过对比选择螺旋天线单元作为组阵单元.对该天线阵列的回波损耗、3D辐射图、方向图进行了仿真计算和设计.结果该天线阵列在6 ～ 10GHz内具有较好的定向辐射特性,增益达到15dB.进一步优化单元空间分布结构,使天线在相应频段内具有更佳的方向性.通过调整各个馈源的相位差,在不失去增益的同时,可以控制波束的偏转.     

阵列天线互耦补偿技术研究

分析阵列天线的互耦机理,利用电磁散射理论研究阵列天线的散射特性,得到阵列天线的散射矩阵,并根据散射矩阵中的实际物理意义,将矩阵进行分解,推导出阵列天线的互耦补偿公式,避免了复杂的计算,并在实际测试数据的基础上,利用提出的算法进行互耦补偿,验证了该算法的有效性。     

圆锥印刷四臂螺旋天线的分析与设计

提出了一种应用于全球定位系统(GPS)的宽波束圆极化圆锥印刷四臂螺旋天线。数值分析表明螺旋角和螺旋臂的长度是影响波瓣宽度的两个主要因素,文中给出了其变化规律。基于此,我们设计了一个中心频率为1.57542GHz的圆极化圆锥印刷四臂螺旋天线,并制作了模型天线。测试结果显示该天线在中心频率处的3dB波瓣宽度约为200°,满足半球覆盖特性;3dB轴比带宽约为0.35GHz;驻波比在1.5以下的频率范围为1.47~1.6GHz。实验结果和仿真结果吻合良好。     

基于有限元方法的螺旋天线设计

研究了一种用于中短距离通信的螺旋天线,分析了螺旋天线特别是轴向模螺旋天线的基本电磁辐射特性,介绍了有限元方法的基本理论和数值计算过程,并结合有限元法对螺旋天线进行了设计、优化,仿真出该天线的电参数和辐射方向图,然后将设计的天线模型进行通信实验。实验表明圆极化的轴向模螺旋天线通信质量良好,完全达到设计要求。     

双臂圆锥对数螺旋天线的研究

本文利用曲线段三角基展开,伽略金法检验的矩量法对一种非频变天线－双臂圆锥对数螺旋天线进行了分析,通过曲线段拟合线结构以及利用阻抗矩阵的中心对称笥减少计算量。使得计数精度,速度大为提高。本文的方法和程序也适用于平面螺旋和圆柱螺旋天线的设计和计算。文中同时给出大量曲线数据,并将计算结果与文献和实验进行对比,吻合良好。     

Numerical analysis of arbitrarily shaped probe-excited single-armprinted wire antennas

A general integral equation technique is described for analysis of an arbitrarily shaped single-arm printed wire antenna excited through a vertical probe. A unified current integral equation is formulated on the basis of dyadic Green's functions and the reciprocity theorem. The current distribution is obtained by using a parametric moment method in which parameter segments are adopted for the printed wire instead of the commonly employed wire length segments. The radiation field solution involving both the printed antenna and vertical probe is also presented. The validity of the formulation is verified by comparing the numerically obtained input impedance and radiation patterns for a linear antenna and a meander antenna with measured data. A circular open loop and an Archimedian spiral are investigated to illustrate the applicability of the present technique     

Full-wave analysis of quasi-optical structures

A full-wave moment method implementation, using a combination of spatial and spectral domains, is developed for the analysis of quasi-optical systems. An electric field dyadic Green's function, including resonant and nonresonant terms corresponding to coupling from modal and nonmodal fields, is employed in a Galerkin routine. The dyadic Green's function is derived by separately considering paraxial and nonparaxial fields and is much easier to develop than a mixed, scalar and vector, potential Green's function. The driving point impedance of several antenna elements in a quasi-optical open cavity resonator and a 3×3 grid in free space are computed and compared with measurements     

Dyadic Green's functions inside/outside a dielectric elliptical cylinder: theory and application

Dyadic Green's functions in two regions separated by an infinitely long elliptical dielectric cylinder are formulated in this paper. As an application, the plane electromagnetic wave scattering by an isotropic elliptical dielectric cylinder is revisited by applying these dyadic Green's functions and the scattering-to-radiation transform. First, the dyadic Green's functions are formulated and expanded in terms of elliptical vector wave functions. The general equations are derived from the boundary conditions and expressed in matrix form. Then the scattering and transmission coefficients coupled to each other are solved from the matrix equations. To verify the theory developed and its applicability, we revisit the plane electromagnetic wave scattering (of TE- and TM-polarizations) by an infinitely long elliptical cylinder, and consider it as a special case of electromagnetic radiation using the dyadic Green's function technique. The derived equations and computed numerical results are then compared with published results and a good agreement in each case is found. Special cases where the elliptical cylinder degenerates to a circular cylinder and where the material of the cylinder is isorefractive are also considered, and the same analytical solutions in both cases are obtained.     

单层和双层手征介质柱域的并矢格林函数理论及其应用

本文应用散射叠加法,分别导出了单层和双层手征介质圆柱区域中的并矢格林函数。由此分析了位于手征介质圆柱和手征介质圆柱罩中心轴线上点偶极天线的辐射特性。结果表明,通过改变手征介质圆柱的尺寸和手征介质圆柱罩的厚度,可以任意调节辐射场的极化特性。另外,本文给出的并矢格林函数公式还可用于分析柱形手征微带天线的辐射特性。     

Analysis of microstrip antennas on circular-cylindrical substrateswith a dielectric overlay

The use of dyadic Green's functions and the moment method is explored for the solution of microstrip antenna problems on circular cylindrical substrates. The dyadic Green's functions of the electric type are obtained for a medium consisting of three cylindrical dielectric layers concentric with a perfectly conducting cylinder, and integral equations are developed for the evaluation of the electromagnetic fields. The effect of a dielectric overlay on the resonant frequency of a cylindrical-rectangular microstrip antenna is analyzed. The patch is directly fed by means of a microstripline printed along the cylinder axial direction. The results show that the effect of the dielectric overlay is substantial when its relative permittivity and thickness are increased, such that this effect has to be very carefully considered in the design of microstrip antennas     

Cavity-Backed Aperture Antennas with Dielectric and Magnetic Overlay

A method is presented for a full wave analysis of an aperture antenna backed by a rectangular cavity. The antenna may be covered by one or more dielectric and magnetic layers. The aperture antenna may be arbitrarily shaped but must be small compared to the cross section of the cavity. The analysis includes ohmic, dielectric, and magnetic losses in the cavity as well as in the overlay. Deriving a modified magnetic field integral equation, the treatment of the cavity and of the layered overlay is separated. A dyadic Green's function describing the topology of the cavity is formulated in the space domain. Another dyadic Green's function for the layered overlay is derived in the spectral domain. Subsequently, the integral equation is solved by the method of moments. The theoretical treatment is worked out for arbitrarily shaped apertures. Finally, the proposed method is applied to narrow slot antennas backed by rectangular cavities. Some numerical results are compared with experimental data     

An asymptotic closed-form microstrip surface Green's function forthe efficient moment method analysis of mutual coupling in microstripantennas

A relatively simple closed-form asymptotic representation for the single-layer microstrip dyadic surface Green's function is developed. The large parameter in this asymptotic development is proportional to the lateral separation between the source and field points along the air-dielectric interface. This asymptotic solution remains surprisingly accurate even for very small (a few tenths of a free-space wavelength) lateral separation of the source and field points. Thus, using the present asymptotic approximation of the Green's function can lead to a very efficient moment method (MM) solution for the currents on an array of microstrip antenna patches and feed lines. Numerical results based on the efficient MM analysis using the present closed-form asymptotic approximation to the microstrip surface Green's function are given for the mutual coupling between a pair of printed dipoles on a single-layer grounded dielectric slab. The accuracy of the latter calculation is confirmed by comparison with numerical results based on a MM analysis which employs an exact integral representation for the microstrip Green's function     

构造平面分层均匀媒质并矢Green函数的本征谱方法

本文从自由空间中的并矢Green函数出发,引入一种构造平面分层均匀媒质中并矢Green函数的新方法。根据平面分层均匀媒质中不同取向的点源辐射在场点处的响应得到并矢Green函数的谱矢量,进而得出平面分层均匀媒质中并矢Green函数的积分表达式。     

INPUT IMPEDANCE OF MICROSTRIP ANTENNA WITH THICK MULTILAYER SUBSTRATE

A method has been devised to analyze multilayer electrically thick circular mi-crostrip antenna excited by a probe.The current on the probe is taken to be uniform.Thismethod was verified by analysis and experiment of an electrically thick circular microstrip an-tenna with an air gap.Based on the free space electric dyadic Green's function,the field expressionof an horizontal electric dipole(HED),which is located at any point of the multilayer media andpoints in any direction,has been derived.By using this field expression and the Richmond re-action equation,an integral equation in terms of electric current on the patch is formulated.Byproperly choosing current expansion modes,this method can be used for an electrically thick mi-crostrip antenna.The theoretical results agree very well with experimental data for an electricallythick circular microstrip antenna with an air gap.