An algorithm for calculating Green's functions of planar, circular cylindrical and spherical multilayer substrates

The problem of diffraction at the edge of a semi-infinite grounded dielectric slab excited by a line source is investigated. This canonical problem may be used as a reference solution in the high-frequency regime for patch antennas radiating from a finite grounded slab. Both physical optics (PO) and integral equation (IE) approaches are used and compared. The PO formulation is cast in a convenient asymptotic form that neatly describes the diffraction processes associated with the various wave species. The IE, solved by the method of moments, is formulated by enforcing the continuity of the electric field on an infinite aperture orthogonal to the slab. This allows a drastic reduction of unknowns, provided that appropriate entire domain basis functions are used that are shaped to match the asymptotic behavior of the aperture field. Comparison between the PO and IE solutions is presented to determine the range of validity of PO.

Diffraction from a truncated grounded dielectric slab: a comparative full-wave/physical-optics analysis

An efficient numerical-analytical approach is developed to calculate spatial mixed-potential Green's functions for sheet currents placed over a cylindrical circular metal rod with a dielectric substrate. The approach is based on a special annihilation technique, which allows performing the Inverse Fourier Transform in a very effective way. This technique includes numerical-analytical extraction and inversion of cases of 'bad behaviour' of the spectral Green's functions, due to slowly decaying asymptotes and poles. As a result the spatial Green's functions are represented in a form in which the contribution of the source singularity and the surface waves is given by separate terms.

Mixed-potential Green's functions for sheet electric current over metal-dielectric cylindrical structure

Impact behavior of composite antenna array that is conformed around cylindrical bodies

Metasurfaces that manipulate electromagnetic waves have gained significant attention in recent years. The focus has primarily been on planar devices, while many applications require curved surfaces. In this study, the authors propose an analysis approach for cylindrical cascaded (multilayer) metasurfaces. The approach combines the concept of sheet impedance in the spectral domain with a new transmission matrix formulation that is applicable to stratified, canonical curved geometries. Approximate formulas for the sheet impedance of common planar, metallic patterns are also adapted to curved geometries. The reported analysis approach allows one to determine the optimal spectral-domain, azimuthal dependence of a sheet impedance, as well as the best geometrical elements to obtain the required azimuthal variation. The results are verified through several cylindrical metsurface examples.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2017.0465

Modelling Cascaded Cylindrical Metasurfaces Using Sheet Impedances and a Transmission Matrix Formulation

Periodic strips on planar and circular cylindrical substrates: Exact and asymptotic analysis

We have developed a computer program which calculates radiation patterns of an array of N/spl times/N patch antennas located above or inside a multilayer circular cylindrical structure by using the spectral domain approach. In the present paper, we use the program to study the effects of the curvature of the structure on the radiation pattern. The results show that the radiation pattern in the azimuthal direction is strongly dependent on the cylinder radius but much less so in the elevation direction. The results also show that the array exhibits high sidelobes which can be reduced by making the element spacing smaller than is necessary in the planar array.

Effect of element spacing and curvature on the radiation patterns of patch antenna arrays mounted on cylindrical multilayer structures

Input impedance and radiation pattern of patch on multilayer cylinder

In this paper we present a program for the analysis of conformal arrays. The program can analyze finite arrays of arbitrarily-oriented rectangular patches mounted on a circular cylindrical multilayer structure. We use the element-by-element approach in the spectral domain, together with the moment method, to calculate the unknown currents on the patches and then the radiation pattern, input and mutual impedances. In order to verify the program, we have built a laboratory model on which we have measured the mutual coupling between two patches for different spacings, as a function of frequency. The radiation pattern of an array of 45/spl deg/ tilted patch antennas has also been calculated and compared with measurements found in literature.

Silvia Raffaelli

Papers

Periodic strips on planar and circular cylindrical substrates: Exact and asymptotic analysis

Effect of element spacing and curvature on the radiation patterns of patch antenna arrays mounted on cylindrical multilayer structures

Input impedance and radiation pattern of patch on multilayer cylinder

Theoretical and experimental study of rectangular patches mounted on multilayer circular cylinder

Radiation pattern and input impedance of arbitrarily oriented patches on a two-dimensional structure