Browsing by Subject "Dielectrics."

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Open Access
Development of closed-form Green's functions to investigate apertures on a pec circular cylinder covered with dielectric layer(s)
(2009) Akyüz, Murat Sencer
Closed-form Green’s function representations for magnetic sources, which is in general used to represent aperture type antennas on conducting surfaces, are developed for a cylindrically stratified media. The resultant expressions are valid for almost all possible placements of source and observation points including the cases where ρ = ρ 0 and φ = φ 0 . Hence, they can be used in a Method of Moments solution procedure. In the course of obtaining these expressions, the conventional spectral domain Green’s function representations for magnetic sources are reorganized in order to handle relatively large cylinders and the axial line problem. Available acceleration techniques that exist in the literature are implemented to perform the summation over the cylindrical eigenmodes efficiently and to handle some numerical problems along the kz integration path. Then, the resulting expressions are transformed to the spatial domain using the discrete complex image method with the help of the generalized pencil of function method, where a two-level approach is used. It should be noted that a similar methodology has recently been developed for electrical sources and very accurate results have been presented. In this work, its magnetic source counterpart has been developed. Numerical results are presented in two different forms: (a) ρ 6= ρ 0 ; the magnetic source is on the conducting cylinder, which forms the innermost layer of the dielectric coated cylinder. This is a typical scenario for the radiation problem of aperture type antennas. (b) ρ = ρ 0 ; both the magnetic source and the observations points are on the conducting cylinder which forms the innermost layer. There is a singledielectric layer on the top of them. This is a typical scenario for the mutual coupling between aperture type antennas.
Open Access
A study of line source fields transmitted through a 2D circular dielectric radome or a slab
(1996) Bircan, Anil
In this thesis, far field solutions for the real and complex line sources surrounded by a cylindrical dielectric shell (radonie) are obtained in both E and H polarizations. These far fields for the radoine model are then compared with the ones transmitted through an infinite dielectric slab. The motivation is that as the far field in the main beam direction is concerned, the radome of large radius can be cipproximated by an infinite dielectric slab. It is clear that the fields of the cylindrical shell (radome) is expressed in terms of cylindrical functions whereas for the slab, the fields are given through Sommerfeld integrals. By applying the saddle point integration techniques to the Sommerfeld integrals, the radiated fields of the slab are numerically calculated and compared with the fields of the dielectric shell. The source is taken as a line source, l)ut it can also simulate a beam field l)y the complex source a.|)proach. d'he study gives a better understanding of the reflector antennas covered with di('lectric radomes.