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1.
背腔式微带天线电磁散射分析的FEM/PO-PTD方法 总被引:3,自引:0,他引:3
将一种新的混合方法-FEM/PO-PTD方法,应用于分析计算背腔式微带天线的电磁散射特性。通过无穷大接地导体平面上矩形背腔式微带天线的RCS计算,验证了该方法的正确性。在此基础上,计算了两组有限尺寸金属载体上背腔式微带天线的RCS曲线,理论分析与计算结果表明,该混合方法具有计算机内存需求少、计算时间短等优点。 相似文献
2.
Study of the capacitively fed microstrip antenna element 总被引:2,自引:0,他引:2
《Antennas and Propagation, IEEE Transactions on》1994,42(12):1648-1652
The moment method is used to solve the integral equations describing the capacitively fed rectangular microstrip antenna element. This element consists of a ground plane, a radiating patch, and a small patch located between ground plane and radiating patch. The small patch is fed by a coaxial probe. It excites the radiating patch through capacitive coupling. After checking the accuracy by comparing calculated and measured results, the effect of the capacitor patch is analyzed theoretically. A procedure is given to determine capacitor patches which yield elements matched to the coaxial feed. It is shown how a matched configuration can be found for a given capacitor patch height 相似文献
3.
Focardi P. Freni A. Maci S. Vecchi G. 《Antennas and Propagation, IEEE Transactions on》2005,53(2):601-607
This paper presents a procedure to reduce the computational effort for the full-wave analysis of corrugated or stepped rectangular horns/cavities, open-ended on an infinite ground plane. This procedure, framed in the method of moments (MoM), is based on the construction of appropriate basis functions generated by solving the problem of one element in isolation. These functions are termed "synthetic aperture functions" (SAF); being numerical solutions of a physical problem, they have the adequate contents of high-order waveguide modes which allow the proper storage of local reactive energy. They also include a good approximation of the correct edge behavior. The technique reveals a significant reduction of computational resources compared to an ordinary MoM solution, especially for a large number of radiating elements 相似文献
4.
A finite element method (FEM) is implemented to compute the radar cross section of a two-dimensional (2D) cavity embedded in an infinite ground plane. The method is based on the variational formulation which uses the Fourier transform to couple the fields outside the cavity and those inside the cavity; hence, the scattering problem can be reduced to a bounded domain. The convergence of the discrete finite element problem is analyzed. Numerical results are presented and compared with those obtained by the standard finite element-Green function method and by the 2D integral equation method. 相似文献
5.
《Antennas and Propagation, IEEE Transactions on》2008,56(9):2801-2809
6.
A novel numerical technique is proposed for the electromagnetic characterization of the scattering by a three-dimensional cavity-backed aperture in an infinite ground plane. The technique combines the finite element and boundary integral methods to formulate a system of equations for the solution of the aperture fields and those inside the cavity. Specifically, the finite element method is used to formulate the fields in the cavity region, and the boundary integral approach is used in conjunction with the equivalence principle to represent the fields above the ground plane. Unlike traditional approaches, the proposed technique does not require a knowledge of the cavity's Green's function and is, therefore, applicable to arbitrary shape depressions and material fillings. Furthermore, the proposed formulation leads to a system having a partly full and partly sparse as well as symmetric and banded matrix which can be solved efficiently using special algorithms 相似文献
7.
Mioc F. Albani M. Focardi P. Maci S. 《Antennas and Propagation, IEEE Transactions on》1999,47(2):408-410
An exact expression in terms of line integration is presented for the near field of a rectangular waveguide modal current distribution, radiating either in free-space or on a perfectly conducting infinite ground plane. This formulation may be used in the framework of a method of moments (MoM) for reducing the computational time 相似文献
8.
9.
Two rectangular wire loops above an infinite ground plane are investigated for broadband circular polarization and impedance matching. Each rectangular loop is connected to each end of a short dipole fed by a coaxial cable through the ground plane. One gap on each loop is introduced to get circular polarization and the gap position controls the sense of circular polarization. The position of the gap, the length of the short dipole, the height of the loop above the ground plane and the shape of the rectangle are very important to get a good axial ratio (AR) and voltage standing-wave ratio (VSWR). The AR bandwidth (/spl les/3 dB) and the VSWR bandwidth (/spl les/2) are 18% and 22%, respectively. The measured and computed results are in good agreement. 相似文献
10.
The problem of a cylindrical cavity-backed suspended stripline (SSL) antenna is viewed as a transition of the SSL to a circular cylindrical waveguide opening into an infinite ground plane. The fields in the waveguide are expanded in terms of TE and TM modes. The effect of the radiating aperture on the modal expansion of the fields is taken into account by introducing reflection coefficients for each mode. The current on the SSL probe is assumed to have sinusoidal distribution. These simplifications reduce the original problem to that of a known radially oriented current residing on a dielectric sheet inside a circular-cylindrical cavity whose top wall has known impedances corresponding to different modes. The Green's function for this modified structure is found and is used to obtain a general expression for the input impedance. This expression is specialized to the case where the SSL probe and the radiating aperture are coupled through the dominant TE 11 mode only. This input impedance is translated to the measurement plane of the antenna. The computed and measured results are found to be in good agreement 相似文献
11.
A dielectric-coated hemispherical conductor mounted on an infinite perfectly conducting ground plane and fed by a coaxial transmission line is investigated. Green's functions for the region above the ground line are derived with separated homogeneous and particular solution parts so as to be compatible with numerical analysis techniques. A magnetic field integral equation is constructed in terms of the unknown annular aperture tangential electric field and is solved by the method of moments. A comparison of the characteristics of the dielectric-coated hemispherical conductor and a flush-mounted coaxial line to an infinite homogeneous region above the ground plane is presented with respected to the tangential aperture electric field, with respect to the tangential aperture electric field, the coaxial line apparent input impedance, and the far radiated field 相似文献
12.
A new analysis technique for infinite phased array antennas was developed and demonstrated. It consists of the finite element method (FEM) in combination with integral equation radiation conditions and a novel periodic boundary condition for 3-D FEM grids. Accurate modeling of rectangular, circular and circular-coaxial feeds is accomplished by enforcing continuity between the FEM solution and several waveguide modes across an aperture in the array's ground plane. The radiation condition above the array is enforced by a periodic integral equation in the form of a Floquet mode summation, thus reducing the solution to that of a single array unit cell. The periodic boundary condition at unit cell side walls is enforced through a matrix transformation. That mathematically “folds” opposing side walls onto each other with a phase shift appropriate to the array lattice and scan angle. The unit cell electric field is expanded in vector finite elements. Galerkin's method is used to cast the problem as a matrix equation, which is solved by the conjugate gradient method. A general-purpose computer code was developed and validated for cases of open-ended waveguides, microstrip patches, clad monopoles and printed flared notches, showing that the analysis method is accurate and versatile 相似文献
13.
The uniform geometrical theory of diffraction (GTD) is employed for calculating the edge diffracted fields from the finite ground plane of a microstrip antenna. The source field from the radiating patch is calculated by two different methods: the slot theory and the modal expansion theory. Many numerical and measured results are presented to demonstrate the accuracy of the calculations and the finite ground plane edge effect. 相似文献
14.
Ross D.C. Volakis J.L. Anastassiu H.T. 《Antennas and Propagation, IEEE Transactions on》1995,43(3):277-285
With the goal of characterizing jet engine inlets, a hybrid finite element-modal formulation is presented for the analysis of cavities with complex terminations. The finite element method (FEM) is used to find the generalized scattering matrix for an N-port representation of the complex termination. Where N is the number of traveling modes in the cavity. The cavity is assumed to be circular at the termination (engine) but the remainder of the cavity can be of arbitrary cross section. The scattered fields are obtained by tracing the fields back out of the cavity via a high frequency or modal technique with the generalized scattering matrix used in determining the fields at an aperture near the irregular cavity termination. “Proof of concept” results are presented and several issues relating to the implementation of the FEM are addressed. Among these, a new artificial absorber is developed for terminating the FEM mesh and the suitability of edge or node based elements is examined 相似文献
15.
An efficient numerical approach to model antennas that include a microstrip element radiating in the presence of material layers is developed. The class of antennas considered is fed through the ground plane by a coaxial transmission line. The reaction integral equation is formulated by treating the coaxial aperture as part of the antenna. The substrate thickness can be arbitrary, making this numerical technique suitable for high-frequency applications. The effects of the substrate are also included in the analysis. Numerical results are obtained for the current distribution and input impedance. The algorithm is validated with experimental results 相似文献
16.
Bailey M. Beck F. Crosswell W. Jones J. Swift C. 《Antennas and Propagation, IEEE Transactions on》1970,18(3):396-399
Experimental measurements of the admittance of rectangular or circular waveguide-fed apertures illuminating a displaced conducting plate of finite area are compared with calculations where the antenna ground plane and displaced conducting boundary are infinite in extent. Also, included are results where dielectric plugs are placed in the aperture. 相似文献
17.
A method for analyzing infinite arrays of antennas printed on both sides of substrates protruding from a ground plane and covered with a dielectric radome is described. Using the equivalence principle, the array unit cell is decomposed into homogeneous regions where the fields are expressed as Floquet summations, and an inhomogeneous cavity region where the fields can be found by a combination of the method of moments and modal analysis. The approach is rigorous in the sense that the combined effects of the radiating element and feed geometry printed on opposite sides of a protruding substrate are taken into account. The method is quite general, capable of modeling any antenna elements with substrate currents that are perpendicular and/or parallel to the ground plane. In addition, both the radiating and scattering/receiving modes of operation are treated in the analysis. The method is used to calculate the active element impedance of an infinite array of dipoles transmission line-coupled to microstrip feeds. Examples of numerical results are presented for various scan conditions and the effects of a near-field dielectric radome are demonstrated 相似文献
18.
Jui-Ching Cheng Dib N.I. Katehi L.P.B. 《Antennas and Propagation, IEEE Transactions on》1995,43(9):1003-1013
A hybrid technique that combines the method of moments (MoM) and the finite element method (FEM) to analyze cavity-backed patch antennas is presented. This technique features the use of FEM in solving the electromagnetic field distribution in the cavity and the use of MoM in solving integral equations outside the cavity. The results of MoM and FEM are combined through the continuity conditions on the boundary of the cavity. Due to the flexibility of FEM, complex cavities filled with inhomogeneous media can be analyzed by this technique. The results obtained by this hybrid technique are compared to the finite difference time domain (FDTD) results and good agreement is found 相似文献
19.
Adams A.T. Leviatan Y. Nordby K.S. 《Electromagnetic Compatibility, IEEE Transactions on》1983,(4):428-432
The near fields of a radiating rectangular plate placed over and normal to an infinite horizontal ground plane have been analyzed as a function of the electrical size of the plate. Both vertical and horizontal currents are taken into account. Two different methods are used to compute the near fields. The variation of the electric field along the normal to the plate is studied in detail as a function of the electrical length L/? of the plate. The electric-field magnitude decreases as distance r increases until an oscillatory region is encountered about one wavelength from the plate. Oscillations continue until distance is equal to L2 /4?, or one-eighth of the usual far-field distance. The location of various minima and maxima can be predicted by a consideration of Fresnel theory. Comparison is made with the near fields of a circular aperture. 相似文献
20.
A hybrid FD-MoM technique for predicting shielding effectiveness of metallic enclosures with apertures 总被引:1,自引:0,他引:1
In this paper, a hybrid technique combining the finite-difference (FD) method and the method of moments (MoM) in the frequency domain is proposed to predict the shielding effectiveness of rectangular conducting enclosures with apertures under external illumination. The interior and exterior regions of the enclosure are analyzed separately by employing the field equivalence principle. Internal electromagnetic fields are discretized using the (FD) method, while external fields are formulated by the MoM. Enforcement of continuity of the tangential magnetic field over the aperture surface gives the desired equation to solve for electromagnetic fields everywhere. Numerical results for the shielding effectiveness of a rectangular cavity with apertures calculated by the new hybrid technique are presented and validated by comparing with experimental data. 相似文献