Efficient procedure for computing fields created by current modes

An efficient method for computing the fields of large scatterers is presented. The current is expanded in terms of modes defined as complex exponential functions. The modes are represented efficiently by means of spline functions. Analytical expressions have been obtained to compute efficiently the fields due to the current modes.     

EE education in Spain

Engineering education in Spain has a long tradition exceeding 150 years. Its traditional character has always been complemented by an effort to work with the social, industrial and international environment of each era. The last great change has taken place in the last ten years (1986-1996) by: (1) expanding the number of engineering degrees offered; and (2) profoundly changing the various curricula. Spain has a dual system based on two engineering degrees: The Technical Engineer or First Cycle Engineer; and the Engineer or Second Cycle Engineer. Access from one degree to the other is guaranteed by a cyclical education system     

Spectral domain analysis of conducting patches of arbitrarygeometry in multilayer media using the CG-FFT method

A conjugate gradient-fast Fourier transform (CG-FFT) scheme for analyzing finite, flat, metallic patches in multilayer structures is presented. Rooftop and razor-blade functions are considered as basis and testing functions, respectively. An equivalent periodic problem in both domains (real and spectral) is obtained and solved. Aliasing problems are avoided by performing a window on the Green's function. The spectral domain periodicity makes it feasible to take into account almost all the harmonics and to reduce the ripple in the computed current distributions. Nearly all the operations are performed in the spectral domain, including Green's function computations. Several results of convergence rates, current distributions and radar cross-section (RCS) values are given and compare favorably with measurements or results obtained by other methods     

Stationary phase method application for the analysis of radiationof complex 3-D conducting structures

The stationary phase method is used to calculate the radiation pattern of antennas on complex structures. Physical optics (PO) approximation has been applied for the induced currents. The problem is stated directly over the parametric surfaces used to model the geometry and no translation of geometrical formats is required. The integral comes from the contribution of certain points on the surface (specular, boundary and vertices) where the phase term of the integrand presents a stationary behavior. In general, the asymptotic integration behaves similar to the numerical one but being more efficient in execution time than the latter     

Analysis and design of a two-octave polarization rotator formicrowave frequency

The analysis and design of a 45° polarization rotator are presented. A two-octave frequency band is achieved with only three grids of strips, each rotated with respect to the previous one. Over this band the transmission loss is less than 0.5 dB, the circular polarization ratio is less than 2.0 dB, and the major axis of the polarization ellipse forms 45°±3° with respect to the linear polarization direction of the incident plane wave. The analysis method is an original scheme based upon the conjugate-gradient fast Fourier transform (CG-FFT) method to analyze periodic structures and the generalized scattering matrix method to study their connection. A comparison between numerical and measured data is presented     

Method based on physical optics for the computation of the radar cross section including diffraction and double effects of metallic and absorbing bodies modeled with parametric surfaces

A method to compute the monostatic radar cross section (RCS) of complex bodies modeled by nonuniform rational B-spline (NURBS) surfaces is presented. The bodies can be covered by any kind of radar absorbing material (RAM) with electric and/or magnetic losses. Physical optics (PO) is used to obtain the scattered field of each surface. Fresnel coefficients are included in the stationary phase method (SPM) in order to take into account the effect of the RAM material. The contribution of diffraction by edges and double effects is also considered, improving the results of the PO approach. The diffraction is computed by the equivalent current method (ECM). A combination of geometrical optics (GO) with PO and ECM is used for the double reflection and double interaction between edges and surfaces respectively. Some simple cases are shown to validate the proposed method. The reliability of the method to analyzing the effect of covering a realistic target with RAM is also illustrated.     

A scheme to analyze conducting plates of resonant size using theconjugate-gradient method and the fast Fourier transform

A scheme for analyzing electrodynamic problems involving conducting plates of resonant size using the conjugate-gradient (CG) method and the fast Fourier transform (FFT) is presented in detail. The problems are analyzed by solving their corresponding electric-field integral equation. The procedure is made easy and systematic by using a sampling process with rooftop functions to represent the induced current and pulses to average the fields. These functions have been widely used in moment-method (MM) applications. The scheme is an efficient numerical tool, benefiting from the good convergence and low memory requirements of the CG and the low CPU time consumed in performing convolutions with the FFT. In comparison with the MM, the scheme avoids the storage of large matrices and reduces the computer time by an order of magnitude. Several results are presented and compared with analytical, numerical, or measured values that appear in the literature     

FASANT: past computer tool for the analysis of on-board antennas

FASANT is a computer tool for the analysis of antennas on-board satellites, ships, aircraft, and other complex bodies. The structure under analysis, which can be metallic or dielectric (with and/or without losses), must be modeled by plane and/or curved surfaces. The geometrical input files are in DXF format, and can be generated by the most commonly used computer-aided geometrical-design (CAGD) tools. The code can also be applied to the analysis of arrays and arbitrarily shaped reflectors. The kernel of the code is based on the uniform theory of diffraction (UTD). Special algorithms have been developed to speed up the ray-tracing computation for both flat and curved surfaces. FASANT can obtain far-field patterns, field levels at points near the structure, can calculate the mutual coupling between antennas or between array elements, and can show each ray-tracing mechanism     

Method to interpolate induced current with low amount of sample points by means of Bezier surfaces

A new interpolation technique to represent the induced current with a very low amount of sample points and computational cost is presented. The amplitude and phase of the current are represented separately, each one being defined at any point of the scattering surface by an interpolating function, built using Bezier's surfaces.