Browsing by Subject "Green's function methods"

Now showing 1 - 5 of 5

Open Access
Analysis of slotted sectoral waveguides embedded in cylindrically stratified media using closed-form Green's function representations
(IEEE, 2013) Kalfa, Mert; Erturk, Vakur B.
Slotted waveguide antenna arrays with dielectric covers are widely used in both military and civil applications due to their low-profile, high power handling capacity, and the ability to conform to the host platform. Conformity is especially required for air platforms where aerodynamics and radar cross section (RCS) of the vehicle are of utmost importance. For an air platform, one or more dielectric layers (monolithic or sandwich radomes) can be used to protect the antenna from the extreme flight conditions. Although the accurate and efficient design and analysis of low-profile conformal slotted waveguide arrays is of great interest, available solution methods in the literature usually suffer in terms of efficiency and memory requirements. Among the available solution methods, one of the widely used solvers are integral equation (IE) based ones that utilize the method of moments (MoM). However, the IE solvers suffer from long matrix fill times, especially when cylindrically stratified media are considered. © 2013 IEEE.
Open Access
Closed-form Green's functions for general sources and stratified media
(Institute of Electrical and Electronics Engineers, 1995-07) Dural, G.; Aksun, M. I.
The closed-form Green's functions of the vector and scalar potentials in the spatial domain are presented for the sources of horizontal electric, magnetic, and vertical electric, magnetic dipoles embedded in general, multilayer, planar media. First, the spectral domain Green's functions in an arbitrary layer are derived analytically from the Green's functions in the source layer by using a recursive algorithm. Then, the spatial domain Green's functions are obtained by adding the contributions of the direct terms, surface waves, and complex images approximated by the Generalized Pencil of Functions Method (GPOF). In the derivations, the main emphasis is to put these closed-form representations in a suitable form for the solution of the mixed potential integral equation (MPIE) by the method of moments in a general three-dimensional geometry. The contributions of this paper are: 1) providing the complete set of closed-form Green's functions in spectral and spatial domains for general stratified media; 2) using the GPOF method, which is more robust and less noise sensitive, in the derivation of the closed-form spatial domain Green's functions; and 3) casting the closed-form Green's functions in a form to provide efficient applications of the method of moments.
Open Access
Comparative evaluation of absorbing boundary conditions using Green's functions for layered media
(Institute of Electrical and Electronics Engineers, 1996-02) Aksun, M. İrşadi; Dural, G.
Absorbing boundary conditions are comparatively studied using the Green's functions of the vector and scalar potentials for multilayer geometries and general sources. Since the absorbing boundaries are introduced as additional layers with predefined reflection coefficients into the calculation of the Green's functions, this approach provides an absolute measure of the effectiveness of different absorbing boundaries. The Green's functions are calculated using different reflection coefficients corresponding to different absorbing boundaries and compared to those obtained with no absorbing boundary. It is observed that the perfectly matched layer (PML) is by far the best among the other absorbing boundary conditions whose reflection coefficients are available.
Open Access
Efficient and robust approach for the derivation of closed-form Green's functions
(IEEE, 1995) Aksun, M. İrşadi
Spatial domain Green's functions for multilayer, planar geometries are cast into closed forms with two-level approximation of the spectral domain representation of the Green's functions. This approach is very robust and much faster compared to the original one-level approximation.
Open Access
A robust approach for the derivation of closed-form Green's functions
(Institute of Electrical and Electronics Engineers, 1996-05) Aksun, M. I.
Spatial-domain Green's functions for multilayer, planar geometries are cast into closed forms with two-level approximation of the spectral-domain representation of the Green's functions. This approach is very robust and much faster compared to the original one-level approximation. Moreover, it does not require the investigation of the spectral-domain behavior of the Green's functions in advance to decide on the parameters of the approximation technique, and it can be applied to any component of the dyadic Green's function with the same ease.