Andrzej A. Kucharski

A method of moments solution for electromagnetic scattering by inhomogeneous dielectric bodies of revolution

A method of calculating the electromagnetic scattering from and internal field distribution of inhomogeneous dielectric bodies of revolution (BOR) is presented. The method uses a typical mode-by-mode solution scheme. The electric flux density is chosen as the unknown quantity, which, together with the special construction of basis and testing functions, enables considerable reduction of the number of unknowns. A key element in this technique is expressing of the azimuthal field components of basis functions in terms of transverse components. A Galerkin testing procedure is used, with special attention put on the efficiency of calculating scalar potential term. Results of calculation for a few classes of dielectric bodies are given and compared with calculations done by other authors.

Efficient Solution of Integral-Equation Based Electromagnetic Problems With the Use of Macromodels

The idea of so-called macromodels is applied to problems of computational electromagnetics involving integral-equation/method-of-moments formulations. It is shown that with the use of equivalence principles, it is possible to exclude a part of the problem, calculate its wideband response without an a priori knowledge of the excitations, and then efficiently combine the result into the original situation. The idea is validated using examples involving slot-excited dielectric resonator antennas.

The Application of Macromodels to the Analysis of a Dielectric Resonator Antenna Excited by a Cavity Backed Slot

The analysis of cavity backed, slot excited dielectric resonator antennas (DRA) is accelerated with the use of a macromodel within the framework of the IE-MoM formulation. The macromodel can be regarded as a projection of complete information about the DRA onto the slot in a wide frequency range, and thus it provides huge reduction in the total number of unknowns. Consequently, this enables a considerable decrease in computation time and makes it possible to curry out fast optimization of a feeding network structure enclosed in a cavity without the need for handling large systems of linear equations associated with the DRA.

Genetic Algorithm Optimization for Broadband Patch Antenna Design

A genetic algorithm (GA) optimization design of patch antenna has been performed using surface integral equation (SIE), method-of-moments (MoM) solution. The electromagnetic engine procedure is based on the Matlab code by Makarov and the idea of GA used is based on the book by Randy L. Haupt. The main aim of the paper is to use GA in finding the proper antenna configuration (parameters) and optimizing its performance in a given frequency range. Sample results are presented, which show the effectiveness of the approach.

Slot Excited Dielectric Resonator Antenna Above a Cavity - Analysis and Experiment

The integral equation -method of moments approach to analyzing a cavity backed, slot excited dielectric resonator antenna is validated experimentally (by measurements). First, the closed rectangular metal box is considered to validate the cavity treatment. Then, the whole DRA structure, i.e. the cavity along with the slot and dielectric resonator, is tested to prove definitively correctness of the approach used.

Genetic algorithm optimization for multiband patch antenna design

A combined method of moment (MoM)/genetic algorithm (GA) numerical procedure for achieving mulitband-frequency characteristics in patch antenna design is demonstrated in this paper. Method of moment (MoM) solution used in simulation relies on RWG (Rao-Wilton-Glisson) edge element. MoM application analyses rectangular patches fed by a coaxial probe and suspended over a ground plane. GA optimization manipulates the impedance matrix of a mother structure in order to detect the optimal patch shape matching the required multiband properties.

The effect of conformality on the electrical properties of small antennas

One of the most desired innovations in modern antenna technology should be the widespread use of conformal designs. Antennas of this kind are expected to be applied primarily in arrays. However, another prospective application for conformal antennas is in handsets or other miniature terminals of mobile and wireless communications systems. The form of the handset and the range of available functions are the prerequisites of the phone market success. Furthermore, the terminal form is strongly related to a possibly large color display, which is no longer a tiny part of the device. Modern multimedia handsets call for multiband antennas, which should feature optimized radiation properties and should possibly be scarce in demand for space. In consequence, it would be an attractive opportunity for designers if antennas could fit into any arbitrary space available in small terminals, specifically in their upper parts. What becomes quite important is that some transmission methods require at least two antennas which must be mounted in the terminal. For these reasons we turned our attention to conformally shaped antennas which can be integrated into handheld terminals in a more flexible way.

Integral equation analysis of shielded dielectric resonators

The method of analysis of shielded dielectric resonators characterized by rotational symmetry is presented. The formulation is based on coupled volume and surface integral equations (VIE/SIE) and enables characterization of inhomogeneous structures. The equations are solved numerically by the method-of-moments (MoM) computational scheme. The example calculation results for axially symmetric TE modes are given.

Planar handset antennas with electronically steerable parameters

The primary objective of developments in wireless communications systems is to increase the density of subscribers simultaneously served by the system. Another major objective is to provide services where high rates of data transmission are needed. This can be achieved by extending the multiple access scheme and by improving channel modulation and coding. There are two major approaches to the multiple access scheme problem-the code division multiple access (CDMA) and the spatial division multiple access (SDMA). Their implementation calls for the use of smart antennas not only at the base station site, but also at the terminals, where antennas of an improved design are recommended. However, the functioning of smart antennas is still far from being well defined, and in this context a variety of concepts have been examined. This paper presents some results of our investigations into terminal antennas with improved properties of their radiation patterns. We focused on two properties-the optimized shape of the radiation pattern and the scanning of the main beam. These properties are needed to suppress interference. Furthermore, owing to the achieved antenna directivity it is feasible to suppress the scattered waves and to decrease intersymbol interference, which is a prerequisite to achieve a high data transmission rate. Unfortunately, each terminal antenna design must comply with the tough miniaturization requirements.

Comparison of the fast multipole method and low rank IE-QR algorithm in the analysis of electromagnetic field in the focal region of a parabolic reflector

This paper describes scattered field calculation in the focal region of a parabolic reflector under uniform plane wave illumination. Method-of-moments (MoM) with integral equations method (IE) is used to calculate the current induced on the reflector. Paraboloid antennas are electrically large objects, so linear equations contain a large number of unknowns (tens of thousands or hundreds). To speed up solution the fast multipole method (FMM) and low rank IE-QR algorithm are involved. Results for ideal and distorted reflectors obtained by MoM, FMM, low rank IE-QR are given and compared with calculations done by other authors.