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The aim of our current work is to construct an algorithm for solving problems of radiation and detection of transient electromagnetic waves in the analysis of permeable bodies. The Time-Domain Finite Element Method (TDFEM) will be used in combination with other numerical techniques. TDFEM is necessary to design — with good precision — the broadband antennas to be used. Here we report the first step achieved in this goal. We designed a Finite Element Method (FEM) code to solve two-dimensional static problems in homogeneous waveguides. In order to test the algorithm constructed, it was applied to calculate dispersion features and to obtain the electromagnetic field in the transversal section of the waveguides for the propagation modes. The results obtained are in good agreement with the analytical results and those of other authors. Currently, we are developing a more complete code that includes time (TDFEM) and that focuses on three-dimensional problems. [ABSTRACT FROM AUTHOR]

A useful method for monostatic RCS reduction of unavoidable shapes in desired frequency bandwidth and angle range is proposed. The proposed method is based on the concept of the random scatterer for RCS reduction and the genetic algorithm for optimization. PO, MEC, and SBR methods are used to obtain RCS. Target shapes whose RCS we want to reduce are basically a plate and finally a scale model tank. Results show that monostatic RCS of a fixed shape can be reduced by the proposed method. [ABSTRACT FROM AUTHOR]

A high performance horn for radio astronomy applications in the 350 GHz band is presented. Perspective application will be in the Atacama Large Millimeter Array radio telescope. The horn is a dual profiled corrugated circular horn designed for constant beam waist position very high return loss and very low cross-polar level. [ABSTRACT FROM AUTHOR]

New expressions for the narrow aperture dimension of the pyramidal horn are presented. They are obtained by using a differential evolution algorithm (DEA), and are used in successfully designing optimum gain pyramidal horns. The DEA is a simple, fast, and robust evolutionary algorithm for solving general type of numeric optimization problems. Design parameters of the horn are determined from the simple and explicit analytical formulas. These formulas do not need the application of the iterative methods, and are not restricted to the high-gain horn designs. The gain of a pyramidal horn is computed without approximating the path length error. Better accuracy with respect to the previous design methods is obtained for various pyramidal horn design examples. [ABSTRACT FROM AUTHOR]

In this paper, the performances of a general MIMO system with arrays at both ends adopting different antenna polarization combinations are studied. Our results show that MIMO systems exploiting the vertically co-polarized antenna arrays at both ends outperform, the horizontally co-polarized combination. The adoption of the orthogonal polarization antenna arrays at both ends can achieve parallel transmission and reception pairs at the expense of some subchannel gains, and thus is an efficient way for enhancing channel capacity in a poor-scattering environment. When cross-polarized antenna combination is used at both ends, both isolation and correlation properties are needed to fully describe the system performance whereas a co-polarized antenna combination scheme can be described by correlation property alone. [ABSTRACT FROM AUTHOR]

The boundary value solution of electromagnetic radiation from an axis-asymmetric slot antenna on a perfectly conducting prolate spheroid coated with a confocal sheath is presented. The electromagnetic fields are expanded in terms of prolate spheroidal vector wave functions. The unknown expansion coefficients are determined from a set of linear equations derived from the application of boundary conditions on the tangential fields' components. Numerical results for radiation patterns and power are presented. It is found that the thickness of the sheath has a significant effect on the radiated fields, and the radiated power is greatly enhanced for certain values of the sheath thickness. [ABSTRACT FROM AUTHOR]

Part I. Proposes a spatial variant radio-wave wideband propagation model for perpendicular streets of urban street grid for microcellular communications. Derivation of an analytical expression of the spatial variant multi-ray channel transfer function; Characteristics of each ray in explicit expressions; Use of the model for antenna diversity and channel capacity problems.