Miodrag S. Tasic

Efficient Analysis of Large Scatterers by Physical Optics Driven Method of Moments

A new iterative procedure is presented that enables method of moment (MoM) solution of scattered field from electrically large and complex perfectly conducting bodies using significantly reduced number of unknown coefficients. In each iteration the body is excited by a plane wave and by the currents, which are obtained as an approximate solution in the previous iteration. The physical optics (PO) and modified PO techniques are used to determine the PO and the correctional PO currents, which are expressed in terms of original MoM basis functions and grouped into macro-basis functions (MBFs). Weighting coefficients of all MBFs are determined from the condition that mean square value of residuum of original MoM matrix equation is minimized. The iterative procedure finishes when the residuum decreases below the maximum allowed value. The accuracy and efficiency of the proposed method are illustrated on two examples: cube scatterer and airplane scatterer. Since the construction of MBFs by PO and modified PO techniques ensures fast convergence to the original MoM solution, the method is named PO driven MoM.

Quadrilateral meshing technique optimized for higher order basis functions

EM modeling of real life structures in the majority of cases starts from an appropriate CAD model. In order to prepare such a model for EM simulation, the model has to be meshed. A novel and efficient quadrilateral mesh technique is presented in this paper. The efficiency and accuracy of this technique is compared with two other quad meshing techniques.

Electromagnetic modeling of complex and electrically large structures

Modern design procedure of antennas, microwave components and EMC facilities usually includes full wave analysis of composite metallic and dielectric structures in frequency domain. One of the methods that can be used for such full wave analysis is method of moments (MoM) applied to surface integral equations (SIEs).

Evaluation of radar cross section of large platforms by the method of moment at PC computers

For electrically large platforms approximating potentials of higher order basis functions can be fully exploited. In this case accurate results can be obtained even with 15 unknowns per wavelength squared. This means that symmetrical platforms with total surface area of 3000 /spl lambda//sup 2/ can be handled on personal computers. In the case of Mirage (whose length is about 12 meters) accurate results can be obtained at 2 GHz, at which its electrical length is 80 /spl lambda/.

Efficient electromagnetic modeling based on automated meshing of polygonal surfaces

Many problems in radar scattering, antenna and microwave fields can be solved by applying the method of moments (MoM) to the surface integral equations (SIEs). The geometry of the analyzed structure is usually modeled by triangular or quadrilateral patches of finite size. Such modeling can be very tedious, when the original structure is of a complicated shape. Very often this complicated shape can be easily represented as a combination of polygonal surfaces. Hence, there is continuous interest for algorithms that subdivide polygons into triangles or quadrilaterals. The main goal of this paper is to present a method for automated meshing of a structure made of polygonal surfaces into convex quadrilateral patches (in such a manner that two neighboring patches have a common edge between two common nodes).

On reducing current expansion order in shadowed regions of scatterers analyzed by method of moments

Efficiency of the method of moments greatly depends on a number of unknowns. In this paper we show that the number of unknowns in a realistic scatterer problem can be reduced up to 50% without significant loss of accuracy in bistatic radar cross section (RCS). The reduction of the number of unknowns is achieved by selective reduction of current expansion order.

Compact UWB MIMO filtennas with dual bandnotch, high isolation and high diversity

This paper presents a 4×4 MIMO filtenna aimed for use with UWB applications. The MIMO filtenna is simulated, fabricated and measured. Obtained simulation and measurement results agree well with each other and have been presented to validate the accuracy of the proposed structure. Measured passband is 2.96–11.56 GHz, with dual bandnotch at 3.5 GHz (S11 = −1.25 dB) and 6.05 GHz (S11 = −2.4 dB). Measured isolation is more than 20 dB between all individual elements of the MIMO filtenna. The behaviour of current within the filtenna at the bandnotch frequencies has been shown. Elements of the filtenna exhibit bi-directional radiation patterns in the E-plane and omnidirectional patterns in the H-plane. The gain and efficiency have also been presented; with the average values being 5.3 dBi and 90% respectively. The Envelope Correlation Coefficient has been calculated from both simulations and measurements; with the measured values being below 0.001 for the passband.

An iterative MoM-based technique for evaluation of bistatic RCS of electrically large scatterers

A simple technique for evaluation of bistatic radar cross-section (RCS) is presented. The technique is purely algebraic and it can be applied to any system of equations obtained by the Method of moments (MoM). Since the MoM matrix need not to be inverted and stored, as with the standard MoM approach, one can expect lowering computational costs. Numerical examples are given, with comparison of bistatic RCS results obtained by the presented technique and by the standard MoM approach.

Analytic solutions of electromagnetic fields in inhomogeneous media

We present guidelines for teaching students how to analytically solve problems that involve inhomogeneous media in electrostatic fields, stationary current fields, and stationary magnetic fields. At the introductory level, the focus is on recognizing classes of problems that can be solved in closed form and applying simple rules, based on comparison with solutions in homogeneous media. At the intermediate level, the focus is on strict proofs based on vector calculus.

Electromagnetic analysis of antennas on large platforms using Physical optics Driven Method of moments

Electromagnetic analysis of antennas on electrically large platforms using numerically exact method of moments (MoM) is enormous burden for a personal computer (PC). In this paper we present novel method which converges toward MoM solution, trough the iterative procedure, without dealing with inversion of large matrices, characteristic for MoM.