带罩天线散射计算的子平面波技术

提出了一种快速有效的带罩天线的RCS计算方法,分析了带罩天线的宽带散射特性.该法基于面电磁流与空域子平面波等效的思想、结合散射场计算的Gordon公式,改进了带罩天线的物理光学法,并详细推导了有关的计算公式,有效解决了工程中大型带罩天线散射场的高效计算问题.通过数值仿真对算法的计算稳定性和效率做了分析,同改进之前相比,该法在保证相同计算精度的条件下,计算效率可以提高2～3个数量级.     

射线跟踪技术分析电大尺寸天线罩的寻迹算法

用几何光学——单一平面波射线跟踪技术解决电大尺寸多层介质罩内电磁波传播问题的关键任务是求解射线与各介质分界面的交点，尤其是为了考虑介质分界面曲率的影响，需要计算波阵面的曲率矩阵，因此有必要用更严格的方法来求射线与曲面的交点。论述了在已知天线罩各介质分界面曲面方程的情况下如何用数值方法中的二分法来计算射线和介质分界面的交点，其算法直观、可靠，适用的曲面方程形式广泛。     

Computer-aided radome analysis

A procedure is presented for predicting by computer the radiation pattern of an antenna in the presence of a radome. The case of a horn antenna radiating through an actual aircraft radome is treated in detail, and a comparison is made between computed and measured antenna patterns. Good agreement between theory and experiment is noted.     

Asymptotic approximations in radome analysis

A detailed analysis is presented of assumptions and limitations of physical optics and stationary phase techniques for radome analysis. A two-dimensional ogival structure with an electric or magnetic line source inside is investigated. A method-of-moments analysis using J.H. Richmond's (1965) polarization current technique is performed to obtain reference results. Physical optics, uniform geometrical theory of diffraction, and stationary phase techniques of order 1 and 2 are analyzed     

Plane wave injection technique to calculate RCS in a 2-D TLM network

A technique for introducing an infinite-appearing plane wave into a two-dimensional transmission line matrix (TLM) network is described. The method has been applied to the calculation of the bistatic RCS for a plane wave normally incident on a conducting square cylinder.<>     

Plane wave integral representation for fields in reverberationchambers

A plane wave integral representation is presented for well-stirred fields in a reverberation chamber. The representation automatically satisfies Maxwell's equations in a source-free region and the statistical properties of the fields are introduced through the angular spectrum, which is taken to be a random variable. Starting with fairly simple and physically appropriate assumptions for the angular spectrum, a number of properties of the electric and magnetic fields and the power received by an antenna or a test object are derived. Many of these properties and test object responses are in agreement with other theories or with measured results. An important result for radiated immunity testing is that the ensemble (stirring) average of received power is equal to the average over plane wave incidence and polarization     

Optimization of two-dimensional radome boresight error performanceusing simulated annealing technique

A systematic approach to radome design is presented. The problem is formulated as a global optimization procedure such that the radome performance is optimized by properly adjusting the thickness of the radome layer over the entire radome surface. In this approach the thickness profile is parameterized via B-splines representation. Simulated annealing technique is applied to finding the best thickness profile so that the maximum boresight error is reduced to as small as possible over the entire range of the antenna look angle. A two-dimensional design example is given. The best possible thickness profile is found and the boresight error is reduced considerably compared to that due to a uniform layer. The method is general and can be applied without difficulty to other realistic three-dimensional radomes of arbitrary shapes     

Scattering of the electromagnetic wave by a phased antenna array with consideration for the radome

A model for calculating the field scattered by the antenna of an aircraft radar with consideration for the radome is described. Backscattering patterns of phased antenna arrays with and without a radome are presented. Substantial contribution of diffraction lobes into the radar visibility of the antenna is noted.     

Catia aided radome analysis using geometric optics method

In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance of electric large three-dimensional dielectric radome-enclosed antenna of arbitrary contour shape. The surfaces of the radome are approximated by planar triangular patches, the influences of various number of patches on power transmission coefficient and Insertion Phase Delay (IPD) via an ogive and a conical radome are discussed by the hybrid method. The simulation results indicate that computational error from planar triangular patches can limit in one percent, meeting the engineering application requirements.     

Plane wave spectrum scattering analysis of near-field obstacle effects on directive antenna patterns

A plane wave spectrum scattering analysis of the effects of a near-zone obstacle on the pattern performance of a directive antenna is discussed. The free-space azimuth monopulse antenna is characterized by its sum and difference mode plane wave spectra, and a computed plane wave scattering dyad is used to characterize the scattering by a metallic right circular cylinder when it is excited by the incident antenna spectra. An efficient computer algorithm has been developed to compute the far-zone scattered and total fields for the antenna/cylinder system. Extensive experimental data have been obtained, and the patterns calculated using the present analysis are in agreement with the measured data.     

宽带天线罩物理光学算法中的自适应网格技术

任意形状天线罩物理光学算法中，需要将天线罩外形网格化，由于宽带天线罩工作带宽校宽，固定尺寸网格模型无法满足表面积分一致性收敛要求，特别是在高频端，在工作站的UG平台上也无法生成极细化网格。本文提出了一种自适应的网格细化技术，以低频网格为基础，随频率自动细化网格，实现了表面积分的一致性收敛，在保证精度的前提下，使计算时间最小化。     

Plane wave diffraction by dielectric gratings finite-differenceformulation

Plane-wave diffraction by dielectric gratings of arbitrary profile (groove shape and size) is analyzed using an analytical-numerical technique. The solution method is simple, general, and numerically efficient. It involves expansion in a Fourier series of the periodic permittivity function in the inhomogeneous grating region and application of the finite differences to solve numerically the inhomogeneous vector wave equation in the region. The obliquely incident radiation is of linear polarization with either of its fields parallel to the rulings. Numerical results are presented for several gratings to demonstrate the convergence, accuracy, and reliability of the method. These also show the effect of the grating profile on its diffraction characteristics     

Plane wave pulse propagation through random media

The theory of plane wave pulse propagation through a random medium, under the forward-scattering assumption is presented. Since pulse propagation characteristics are determined by two-frequency mutual coherence functionGamma, a set of normalized curves is given forGammafor different propagation parameters (operating frequency, propagation distance, turbulence strength or density of scatterers, etc.). From the curves one can obtain the coherence bandwidth of a wave for a variety of situations. A received pulse form due to an input delta function is given in a normalized form which is applicable to the whole range of strong fluctuation. The results are applied to optical pulse propagation in dense clouds. It is shown that the high data rate optical pulse communication through clouds may be limited due to a narrow coherence bandwidth of the order of megahertz. A good agreement between the theoretical prediction and the available experimental data has been demonstrated for both the received pulse shapes and the pulse durations of an optical pulse in clouds.     

Plane wave propagation in uniaxial bianisotropic medium

The uniaxial bianisotropic medium is a generalisation of the bi-isotropic and chiral media which recently have been subject to intensive research. Such a medium results, for example, when microscopic helices with parallel axes are positioned in a host dielectric in random locations. Plane wave propagation in such a medium is studied and a simple solution for the dispersion equation is found. Numerical examples for the wave number surfaces of the medium are given.<>     

Plane wave diffraction by an impedance step

Plane wave diffraction by two half-planes joined by a step is studied in the case where the half-planes and the step are characterized by different surface impedances. The diffraction problem is first reduced to a modified Wiener-Hopf equation of the second kind whose solution contains an infinite set of constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of the surface impedances and the height of the step, through which the effect of these parameters on the diffraction phenomenon is studied     

A quasi-one-dimensional integration technique for the analysis ofplanar microstrip circuits via MPIE/MoM

The mixed-potential integral-equation approach, using spatial-domain closed-form Green's functions, and discretized with the method-of-moments, is a state-of-the-art method for the analysis of planar microstrip circuits. One of its most time-demanding tasks is the evaluation of the impedance matrix terms, which typically requires the numerical computation of two-dimensional integrals. A method based on suitable changes of coordinates and domains is introduced in this paper in order to reduce such integrals to a quasi-one-dimensional numerical integration, with a substantial enhancement in the efficiency of the analysis, without affecting the accuracy of the approach. Results are given demonstrating, for practical accuracy values, an improvement of typically one order of magnitude in simulation times     

天线与天线罩的矩量法严格建模分析

传统计算天线罩对天线性能的影响,是基于天线的辐射场已知的条件下进行的。这样的计算没有考虑天线罩对天线本身电流分布的影响,尤其当天线罩位于天线近场区域的时候,这样的建模方式将带来严重的误差。利用等效原理和矩量法(MoM)对天线和天线罩进行了严格建模,并研究了天线罩对天线电流及辐射特性的影响。数值计算结果与相关参考文献的结果吻合良好。     

Novel A-sandwich radome design for airborne applications

A novel A-sandwich hybrid variable thickness radome design, based on optimised power reflection, is presented. The radome performance parameters are evaluated accurately by a 3D ray-tracing procedure in conjunction with the aperture integration method. This design is demonstrated to be a better choice when multiple performance parameters need to be satisfied simultaneously.     

Plane wave diffraction by a thick-walled parallel-plate impedancewaveguide

The diffraction of E-polarized plane waves by a thick-walled parallel-plate impedance waveguide is investigated rigorously by using the Fourier transform technique in conjunction with the mode-matching method. This mixed method of formulation gives rise to a scalar Wiener-Hopf equation of the second kind, the solution of which contains infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of the plate impedances, plate thickness, and the distance between the plates through which the effect of these parameters on the diffraction phenomenon are studied