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 circular reflectors by complex source-dual series approach

In the present paper, two dimensional circular reflector antennas are analyzed by a rigorous analytical-numerical technique for both E and H polarization cases. The method is used in combination with the complex source approach. The convergence of the solution is guaranteed and any desired accuracy can be obtained. Some principal results of reflector antennas are examined by the exact circular reflector solution

A Hybrid Approach in the Fast Modelling of 2D Scattering From PEC Strip Using Nystrom Algortihm and the Beam Type Green's Function

The method of moments (MoM) procedure was combined with the complex source point (CSP) type Green's function to obtain faster solutions. Even though by this way, the cpu times are reduced drastically for large scatterers, the accuracy of this combination of MoM and CSP type Green's function is not better than the original MoM. On the other hand, here we performed a combination between Nystrom method and a special Green's function having a beam type radiation. Then it is expected to obtain more accurate data compare to MoM due to the convergent nature of Nystrom algorithm. It is also obtained the better running time performance than the original Nystrom method. Also this beam type of Green's function is derived from a general formulation of surface equivalence theorem and so the beam waist on the scatterer can be adjusted to a small value. The results are demonstrated on a single flat PEC strip and these statements are verified in the numerical results by comparing the RCS patterns. It is seen that the RCS patterns are very similar to original Nystrom case. Also the convergence of the results can be seen in the relative error plots for the total scattering cross section

Analysis of a cylindrical reflector antenna encased in a concentric dielectric radome with a resistive or PEC inner circular grating

A regularized solution is presented for a two-dimensional circular reflector antenna system inside a concentric dielectric radome reinforced by an inner resistive circular grating. The directive radiation pattern of the feed antenna is simulated by a Complex Point Source method. Furthermore for a very small resistivity case, an approximate solution for the same problem is presented by considering the grating material is made up of perfectly electric conductor. In this problem, the thickness of the dielectric radome may be arbitrary but the grating material thickness has to be very small compared to the free space wavelength. Various radiation characteristics are obtained and accuracy and convergence of the results are numerically verified. Furthermore, it is shown that a properly located two-element grating can be improving the overall directivity of the reflector antenna system

A Novel Impedance Matrix Localization for the Fast Modeling of 2D Electromagnetic Scattering Using the Localized Green's Function

© 2019 IEEE.In the computation of the electromagnetic wave scattering, the different techniques can be combined together as hybrid methods. The Complex Source Point (CSP) techniques can also be used for this purpose and combined with the Method of Moments (MoM) easily. In 2D scattering problems, the CSP method can be used to convert an isotropic line source radiation to a directive beam with a similar type Green's function expression. By using this CSP type Green's function, the surface current radiates as a beam nature and the interaction between the far elements can be approximated as zero. Hence, the main matrix was strongly localized. But in this study, a surface field distribution in finite width is introduced to the formulation and it is used in the definition of a new Green's function. This new Green's function has a beam aperture localized on the surface and its beam width can be reduced to a few basis function levels by using a generalized pencil of beam function (GPOF) method. This localization of Green's function gives rise to the sparsity in the main matrix. Then the memory storage and the overall running times become smaller so that the larger sizes can be modeled with the smaller computational times

Analysis of circular reflector antenna covered by concentric dielectric radome

The radiation from a two-dimensional cylindrical reflector antenna with a concentric dielectric radome is analyzed in an accurate manner for both H and E polarization cases, The problem is first formulated in terms of the dual series equations, and then it is regularized by using Riemann-Hilbert problem technique. The resulting matric equation is solved numerically, with a guaranteed accuracy, and sufficiently 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-fed reflector antenna geometries in this study

Fast modeling of electromagnetic scattering from 2D electrically large PEC objects using the complex line source type Green's function

This study introduces an alternative approach to the numerical solution of two-dimensional (2D) electromagnetic scattering problems by a numerical method of moments (MoM). The real source position vector is replaced by a complex quantity, then Green's function generates a complex source point beam, therefore the interactions between the far zone elements in the impedance matrix are neglected, except the basis functions near to the edges, strongly localizing the impedance matrix. The memory storage increases with the number of edges, but for a fixed number of the edges, it is linearly proportional with N, i.e. O(N). Consequently, the overall running time can be drastically reduced and the far zone scattering pattern and the near field can be found. The proposed procedure is first explained for the single perfectly electrically conducting (PEC) strip geometry, then extended to the scattering by 2D PEC objects with closed polygonal cross-sections. Numerical results are presented for a strip and a square cylinder in both polarizations. The relative errors are also compared with the standard MoM

Reflection and transmission properties of a graphene-dielectric-thin resistive layer structure in the THz range

We studied two-dimensional planar dielectric slab, sandwiched by graphene and thin resistive layer from two sides. Problem geometry is illuminated by a H-polarized electromagnetic plane wave from upper side. It is expected to observe the reflection and transmission performance of such a composite slab geometry depending on the electrical and geometrical parameters. We used the local reflection and transmission coefficients method to determine the overall performance. It is seen that the proper selection of the electrical resistivity of the thin resistive layer reduces the reflection from lower boundary of slab and the electrical thickness becomes less important for high THz range. Then, the geometry turns to be an air-dielectric interface. This is a novel finding and completely different from the pure dielectric slab without coatings which has frequency dependent characteristics. Also higher reflections are observed due to the higher conductivity of graphene in the low THz range. Furthermore, a sample finite plate is constructed in a same manner and it is modeled by using CST software. Presented method using equivalent 2D profile model and CST results are compared and very good consistency is observed. In both cases, the reflection can be controlled with the chemical potential at low THz range and the selection of the relative permittivity of the dielectric material determines the reflectance level at higher THz scale. We demonstrate these statements in the numerical results section for various problem parameters and angle of incidence

Evaluation of the E-polarization focusing ability in Thz range for microsize cylindrical parabolic reflector made of thin dielectric layer sandwiched between graphene

We consider two-dimensional (2-D) thin dielectric parabolic reflector, covered with graphene from both sides, illuminated symmetrically by an E-polarized electromagnetic plane wave. Our aim is to estimate the focussing ability of such a composite reflector depending on the graphene parameters. We use a version of the two-side generalized boundary condition, modified for a thin multilayer case. The scattering is formulated as an electromagnetic boundary-value problem; it is cast to a set of two coupled singular integral equations that are further subjected to analytical regularisation based on the known Riemann-Hilbert problem solution. Thanks to this procedure, the numerical results are computed from a Fredholm second-kind matrix equation that guarantees convergence and provides easily controlled accuracy. In the lower part of the THz range, high values of the focusing ability are observed even for a thin reflector; they are greater than for a purely dielectric reflector and a free standing graphene reflector. On the other hand, a regime of almost full transparency, intrinsic for the dielectric layer, can spoil focusing ability. Novel aspect is that the location in frequency of this effect can be controlled, in wide range, by changing the chemical potential of graphene

Localized Green's function using a beam-pattern for the fast modeling of 2D electromagnetic scattering

This study presents an alternative approach to the numerical solution of 2D electromagnetic scattering problems using a hybrid numerical technique based on a beam pattern function combined with the method of moments (MoM). A surface field distribution with finite width radiates outward, and it is used to define the new Green's function. This new Green's function has a beam aperture localized on the surface, and its beam width can be reduced to a few basis function levels by using a generalized pencil of beam function method (GPOF). This localization of the new Green's function brings to the sparsity in the main matrix. Then, the memory storage and the overall running times are reduced significantly by applying this localized radiation of Green's function. Numerical results have been presented in both polarizations for the single perfectly electrically conducting (PEC) strip geometry and 2D PEC objects with closed polygonal cross-sections such as square, triangle and arbitrary shapes