Accurate Simulation of Reflector Antennas by the Complex Source-Dual Series Approach

Cataloged from PDF version of article.The radiation from circular cylindrical reflector antennas is treated in an accurate manner for both polarizations. The problem is first formulated in terms of the dual series equations and then is regularized by the Riemann-Hilbert problem technique. The resulting matrix equation is solved numeridy with a guaranteed accuracy, and remarkably Little CPU time is needed. The feed directivity is included in the analysis by the complex source point method. Various characteristic patterns are obtained for the front and offset-fed reflector antenna geometries with this analysis, and some comparisons are made with the high frequency techniques. The directivity and radiated power properties are also studied

Analysis of the elliptic-profile cylindrical reflector with a non-uniform resistivity using the complex source and dual-series approach: H-polarization case

Cataloged from PDF version of article.An elliptic-profile reflector with varying resistivity is analyzed under the illumination by an H-polarized beam generated by a complex-source-point (CSP) feed. The emphasis is done on the focusing ability that is potentially important in the applications in the optical range related to the partially transparent mirrors. We formulate the corresponding electromagnetic boundary-value problem and derive a singular integral equation from the resistive-surface boundary conditions. This equation is treated with the aid of the regularization technique called Riemann Hilbert Problem approach, which inverts the stronger singular part analytically, and converted to an infinite-matrix equation of the Fredholm 2nd kind. The resulting numerical algorithm has guaranteed convergence. This type of solution provides more accurate and faster results compared to the known method of moments. In the computations, a CSP feed is placed into a more distant geometrical focus of the elliptic reflector, and the near-field values at the closer focus are plotted and discussed. Various far- field radiation patterns including those for the non-uniform resistive variation on the reflector are also presented

Analysis of an arbitrary conic section profile cylindrical reflector antenna, H-polarization case

Cataloged from PDF version of article.Two-dimensional scattering of waves by a perfectly electric conducting reflector having arbitrary smooth profile is studied in the H-polarization case. This is done by reducing the mixed-potential integral equation to the dual-series equations and carrying out analytical regularization. To simulate a realistic primary feed, directive incident field is taken as a complex source point beam. The proposed algorithm shows convergence and efficiency. The far field characteristics are presented for the reflectors shaped as quite large-size curved strips of elliptic, parabolic, and hyperbolic profiles

Integral equation anlaysis of an arbitrary-profile and varying-resistivity cylindrical reflector illuminated by an E-polarized complex-source-point beam

Cataloged from PDF version of article.A two-dimensional reflector with resistive-type boundary conditions and varying resistivity is considered. The incident wave is a beam emitted by a complex-source-point feed simulating an aperture source. The problem is formulated as an electromagnetic time-harmonic boundary value problem and cast into the electric field integral equation form. This is a Fredholm second kind equation that can be solved numerically in several ways. We develop a Galerkin projection scheme with entire-domain expansion functions defined on an auxiliary circle and demonstrate its advantage over a conventional moment-method solution in terms of faster convergence. Hence, larger reflectors can be computed with a higher accuracy. The results presented relate to the elliptic, parabolic, and hyperbolic profile reflectors fed by in-focus feeds. They demonstrate that a partially or fully resistive parabolic reflector is able to form a sharp main beam of the far-field pattern in the forward half-space; however, partial transparency leads to a drop in the overall directivity of emission due to the leakage of the field to the shadow half-space. This can be avoided if only small parts of the reflector near the edges are made resistive, with resisitivity increasing to the edge. © 2009 Optical Society of Americ

Focusing ability of a microsize graphene-based cylindrical reflector in the THz range illuminated by electromagnetic plane wave

The scattering of the H-polarized plane wave by a two-dimensional (2-D) parabolic reflector made of graphene placed in the free space is simulated by using the Method of Analytical Regularization (MAR) technique. The total scattering cross-section and absorption cross-section are computed, together with the field magnitude in the geometrical focus of reflector. The surface plasmon resonances are observed. Besides, the focusing ability of the reflector is studied in dependence of the chemical potential of the graphene. © 2016 IEEE

Analysis of an arbitrary-profile, cylindrical, impedance reflector surface illuminated by an E-polarized complex line source beam

Cataloged from PDF version of article.Electromagnetic scattering from a cylindrical reflector surface having an arbitrary conic section profile is studied. We assumed an electrically thin layer antenna illuminated by a complex line source in E-polarization mode. Our boundary value formulation, without loss of generality, involves an integral equation approach having impedance-type thin-layer boundary conditions. For simplicity, we also considered both faces of the reflector of the same uniform impedance value. Our computation employs the Method of Analytical Regularization (MAR) technique: the integral equations are converted into the discrete Fourier transform domain yielding two coupled dual series equations, which are then solved by the Fourier inversion and Riemann Hilbert Problem techniques. We demonstrate the accuracy and the convergence behaviors of our numerically solved MAR results that can serve as an accurate benchmark for comparison with widely used results obtained by approximate boundary conditions

On the elemination of infinities in the PO component of equivalent edge currents

Equivalent edge currents for the Physical Optics (PO) contribution to the edge diffraction are derived by choosing a proper coordinate system for a half plane. It is seen that these expressions for the PO component are free from singularities except at shadow and reflection boundaries on the Keller Cone. To find the total diffracted field, the expressions for the fringe contribution given earlier by Michaeli should be used along with the PO contribution obtained here. The procedure is applied to the problems of backscattering from square and triangular plates. Higher order diffractions are also accounted for by combining the equivalent currents with the Uniform Theory of Diffraction (UTD). The results obtained are compared with previous solutions and measured data. © 1993

Focusing of THz waves with a microsize parabolic reflector made of graphene in the free space

Background: The scattering of H- and E-polarized plane waves by a two-dimensional (2-D) parabolic reflector made of graphene and placed in the free space is studied numerically. Methods: To obtain accurate results we use the Method of Analytical Regularization. Results: The total scattering cross-section and the absorption cross-section are computed, together with the field magnitude in the geometrical focus of reflector. The surface plasmon resonances are observed in the H-case. The focusing ability of the reflector is studied in dependence of graphene’s chemical potential, frequency, and reflector’s depth. Conclusions: It is found that there exists an optimal range of frequencies where the focusing ability reaches maximum values. The reason is the quick degradation of graphene’s surface conductivity with frequency. © 2017, The Author(s)

Analysis of radome covered circular reflectors by complex source-dual series approach

Radiation from a two dimensional reflector antenna covered by a cylindrical radome is analyzed by the complex dual series approach. It is only performed for the electrically polarized incident field. The approach is based on the analytical numerical type regularization technique and not on the moment method. This method gives the exact solution with any desired accuracy and the directivity of the feed antenna can be modelled by using this method. The results can be thought as a reliable data for the validity of approximate solutions. The lossy case and the multilayer radome problems can be solved by the same method

Analysis of thin dielectric cylindrical reflector having an arbitrary conic section profile illuminated by complex line source: H-polarization case

Arbitrary conic section profile and thin dielectric reflector is analyzed by using the Method of Analytical Regularization (MAR) technique based on Riemann-Hilbert problem and Fourier inversion procedures. The reflector surface is assumed to be illuminated by an H-polarized complex line source type feed antenna. The convergence of the solution is verified and some changes in the radiation patterns are obtained especially for rather thicker cases. © 2014 IEEE