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A novel procedure based on characteristic modes (CM) and differential evolution (DE) algorithm is proposed for electrically loaded Yagi-Uda antenna synthesis. In this method, optimal Yagi- Uda antenna designs are realized by electrically loading, other than by tuning the sensitive physical dimensions. The traditional fullwave analysis in objective function evaluations is replaced by a simple summation of the CM, thus the optimization efficiency is greatly improved up to 4 orders. Antenna performances are compared to published results to illustrate the effectiveness of the present method. [ABSTRACT FROM PUBLISHER]

A hybrid method that combines the integral equation (IE) method and Physical Optics (PO) is proposed for efficient analysis of slot arrays enclosed in an electrically large radome. The integral equations are applied over the aperture of the slot antenna and the tip region of the radome by enforcing continuity of the tangential magnetic or electric field. Equivalent PO currents are assumed on the relatively smooth region of the radome walls, induced by the radiated fields from the antenna. The radiated fields due to the PO currents on the radome are coupled back to the integral equations to account for interactions between the radome and the antenna, as well as the interactions between the tip and other parts of the radome. This method leads to considerable reduction in memory and computational time, since PO is applied to a large part of the electrically large radome, with unknown currents defined only on the aperture of the slot antenna and the small tip region of the radome. Better efficiency can be attained if the integral equation is applied only to the slot aperture and the entire radome wall taken as the PO region, with acceptable degradation in accuracy. [ABSTRACT FROM AUTHOR]

In this paper, the authors present a new and fast implementation of the field iterative method (FIM) with the fast far-field approximation (FAFFA). The new implementation of FAFFA-FIM can significantly reduce the computational expenses of the FIM. Numerical simulations for scattering from cavities verify the proposed FAFFA-FIM. The memory requirement and CPU time per iteration of the FAFFA-FIM are O(N) and O(N1.5), respectively, and the CPU time per iteration of the FAFFA-FIM can be further reduced to O(N4/3). [ABSTRACT FROM AUTHOR]

Replies to the comments of R.C. Acar and G. Dural to the authors' article "A Complete Set of Spatial-Domain Dyadic Green's Function Components for Cylindrically Stratified Media in Fast Computation Form." Typographic errors in the paper; Agreement with the suggested corrections.

In this paper, the authors use the adaptive integral method (AIM) to simulate the electromagnetic scattering from large complex PEC objects. The first problem that we have investigated is the scattering from a dihedral corner reflector that may lead to a better understanding of scattering mechanisms and properties of more complex geometries. The second problem investigated in scattering from a multiplate structure consisting of trapezoidal plates. The third problem investigated is the scattering from a composite PEC sphere and plate structure. The AIM simulation results are compared to the results obtained using the physical optics (PO) technique. In order to test the capability of AIM further, an aircraft model with many patches of flat surfaces has been built for this purpose. This mesh generation and the measurement of the scattering pattern of the aircraft model have been carried out by us. With the mesh and measurement results of the aircraft model, the simulation was carried out using AIM. The numerical results of all the test cases show that the AIM is an efficient method for analyzing electromagnetic scattering from large complex PEC objects. [ABSTRACT FROM AUTHOR]

Numerical characterizationof electromagnetic waves in cylindrically multilayered structures can be efficiently and rigorously performed by employing the method of moments (MoM) in spatial-domain. Thus the idea of obtaining spatial-domain Greens' functions in closed form or fast computational form was proposed [1] and since then many useful results were obtained for planar layered media. For cylindrically layered media, the closed form Green's functions in spatial-domain were reported in [2], where the spatial-domain Green's function components due to z- and φ-oriented electrical and magnetic sources have been obtained using the generalized pencil of function (GPOF) method. This paper, as a further extension, presents spatial-domain Green's function components in fast computational form due to ρ-oriented electrical source embedded in cylindrically layered media. The Green's function components in approximate but fast computational form are compaerd with the exact Green's function components obtained from direct numerical evaluations of the corresponding integrals, and a good agreement between the fast computational form and the exact form. Furthermore, the spatial-domain Green's function compnents due to z- and φ-oriented electrical and magnetic sources have also been obtained but for all the possible azimuth angles. [ABSTRACT FROM AUTHOR]

Examines the electromagnetic scattering from a perfectly electric conducting target located above or below rough surface for the case of TM polarization, using the method of moments. Use of the rough surface with Gaussian profile to emulate the realistic situation of a statistically-rough surface; Use of the tapered incident wave to reduce the truncation error; Calculation of the angular correlational function.

Presents a study which described an efficient analysis of a microstrip antenna in multilayered media using the method of moments. Formulations; Results and discussion; Conclusion.

The analysis of electromagnetic scattering from cavity structure is very important to many practical applications. The field iterative method (FIM) is one of the promising methods to deal with the cavity problem. In this paper, 3-dimensional (3D) FIM has been implemented using Rao-Wilton-Glisson (RWG) basis function and an accurate equivalent model of the cavity. Two testing procedures, a newly developed point matching and conventional Galerkin's methods, have been discussed for better and simpler implementation of the 3D FIM. Numerical results show that the accuracy of the 3D implementation of FIM using the newly developed point matching method is the same as that of the conventional Galerkin's method. The numerical results also show that the simpler implementation of 3D FIM using the point matching method converges very fast for all the tested cases. [ABSTRACT FROM AUTHOR]

The method of moments (MoM) and the electric field integral equations (EFIEs), for both parallel and perpendicular polarization were applied to simulate scattering from 2D cavity structures. This code employed several matrix equation solvers, such as the LU decomposition, conjugate gradient (CG) method, bi-conjugate gradient (BCG) method, generalized conjugate residual (GCR) method, and generalized minimal residual (GMRES) method. The simulated results can be used for future reference and benchmarking. A comparison on the convergence behavior of the CG, BCG, GCR, and GMRES methods was made for the benchmark geometry, such as offset bend cavity, rectangular waveguide with hub, double-bend S-shaped cavity, etc. Some comments on the performance of the various iterative solvers will be highlighted. [ABSTRACT FROM AUTHOR]