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Two general approaches to multiminima optimization are considered. The first approach is based on repetition of a single minima method (e.g., the Nelder-Mead simplex applied to the best solution in a set of random trials). The second approach is based on a coarse estimation of local minima using initial set of points and local optimization starting from these local minima (e.g., random search as a generator of the initial set of points and Nelder-Mead simplex as a local optimizer). A comparison of various optimization algorithms has been done on one analytical problem and two well-known examples of antenna design. It is found that: a) the multiminima method based on coarse estimation enables finding more minima with smaller number of iterations than that based on repetition, b) the best multiminima methods are comparable with the best single minima methods in a number of iterations needed for finding the global minima, and c) the multiminima method based on coarse estimation restarted with different weighting coefficients of multiobjective cost function enables efficient Pareto optimization. Index Terms--Automated design, black-box optimization functions, heuristic multiminima antenna optimization, hybrid optimization algorithms, Nelder-Mead simplex, Pareto front.

Conservation of energy and power can be, under certain conditions, exactly satisfied in an approximate numerical method. In this paper necessary and sufficient conditions for this property are rigorously derived for the finite-element method (FEM) and the method of moments (MoM). Two boundary formulations of FEM (strong and weak) and three formulations of MoM (MoM/VIE, MoM/SIE for metallic and MoM/SIE for dielectric bodies) were considered for radiation problems in the frequency domain. The concept of error generators--fictitious generators that produce the difference between the approximate and the exact solution--was introduced to state the power conservation property from another aspect. It was proved that, for the appropriate governing equation and the 'conjugated' inner product, power conservation is satisfied if and only if the Galerkin (or equivalent) method is used. However, power conservation is corrupted if an equivalence principle (surface or volume) is utilized in MoM to solve problems in inhomogeneous media. Examples are given to illustrate the power conservation and its possible advantages. Index Terms--Energy conservation, finite-element methods (FEM), method of moments (MoM).

A study was conducted to analyze alternative expressions of doublets and rooftop basis functions that promote continuity equation at the junction. The basic characteristics of such doublets were examined and evaluated against other kinds of doublets. Results indicated that the exact formulation supports the continuity of equation and a constant current component normal to the interconnection.

An infinitesimally thin-square scatterer, of size [Lambda] x [Lambda], excited normally by an incident plane wave, which is polarized along a scatterer edge, is analyzed. The accurate solution of its current distribution is found in the form of double series of basis functions, which automatically satisfy the continuity equation at plate edges and include the edge effect. The coefficients that multiply basis functions are determined starting from the electric field integral equation by using the Galerkin method. The solution obtained for the order of approximation n = 8 is adopted as a benchmark. The corresponding coefficients are tabulated and graphs of such obtained current distribution are given. The solution adopted as a benchmark is applied for comparison of rooftop basis functions and polynomial entire-domain basis functions. The relative error of the mean absolute value of current deviation is used as an error metric. Index Terms - Electromagnetic scattering, moment methods.

Most of the methods that solve the surface integral equation (SIE) by the method of moments (MoM) use triangles and flat quadrilaterals for geometrical modeling. Many complex structures can be easily modeled by quadrilaterals combining spiral super-quadric generatrices and the concept of the body of two generatrices (BoTG). A BoTG is any body that can be obtained from two generatrices by applying a certain rule. Four simple rules for obtaining BoTG's are: 1) generalized rotation; 2) translation; 3) constant cut; and 4) connected generatrices. Spiral super-quadric generatrices enable efficient modeling of circles, arcs, ellipses, squares, rectangles, spirals, etc. Thus, a simple but fairly general algorithm for geometrical modeling is obtained, convenient for implementation in electromagnetic-field solvers.

Monostatic radar cross section (RCS) of an combat aircraft is analyzed using iterative Least Square Method weighted domain decomposition method (LSM weighted DDM). The model of the 200 wavelengths long aircraft is made of perfect electric conductor (PEC). Inlet cavity of the jet engine is included in the model. The inlet has realistic shape, whereas cavity is closed with a PEC on the outlet side. Corresponding model without the inlet is also analyzed--the inlet contour is smoothed, and then it is closed with a PEC. Method of moments (MoM) solution is used as a reference. It is shown that the LSM weighted DDM solution can provide very good solution in just a few iterations if problematic parts of the structure are extracted in separate subdomains. [ABSTRACT FROM AUTHOR]

This paper presents an efficient technique to determine equivalents of towel bar antenna dielectric standoffs in the form of wires with distributed loadings using WIPL-D Pro (3-D EM solver) software. Starting from the product, we will determine its basic characteristics and propose simplifications in modeling for further analysis. Benefits of this technique are simplicity of modeling and fast, but still accurate, simulations. [ABSTRACT FROM AUTHOR]

Design method for band-stop filters (BSFs) that suppress a requested number of spurious bandstops and reduce ripples in the passbands below ~1 dB is proposed. BSF is designed in a form of a cascade of cells, each consisting of steps of equal electrical length, where the number of steps is used to control the number of suppressed spurious bandstops. Analytical formulas are developed that enable initial design of BSF for a given central frequency, depth, and bandwidth of the stopband. Varying the minimum characteristic impedances of initial cells, through an optimization using circuit simulation, the ripples in passbands are reduced below ~1 dB. Using the proposed theory, three filters in microstrip technology, with suppression of 3, 5, and 7 spurious stopbands respectively, were designed, fabricated, and measured. Good agreement between simulated and measured results has been observed. The proposed design can be recommended for filters having broad stop bandwidths, between 40 and 100%. [ABSTRACT FROM PUBLISHER]