scholarly journals Analysis of Arbitrary Reflector Antennas Applying the Geometrical Theory of Diffraction Together with the Master Points Technique

2013 ◽  
Vol 2013 ◽  
pp. 1-13
Author(s):  
María Jesús Algar ◽  
Jose-Ramón Almagro ◽  
Javier Moreno ◽  
Lorena Lozano ◽  
Felipe Cátedra
Keyword(s):  
Method Of Moments ◽  
Near Field ◽  
Complex Geometries ◽  
Geometrical Theory ◽  
Reflector Antennas ◽  
New Approach ◽  
Sampling Points ◽  
Time Requirements ◽  
Geometrical Theory Of Diffraction ◽  
A New Technique

An efficient approach for the analysis of surface conformed reflector antennas fed arbitrarily is presented. The near field in a large number of sampling points in the aperture of the reflector is obtained applying the Geometrical Theory of Diffraction (GTD). A new technique named Master Points has been developed to reduce the complexity of the ray-tracing computations. The combination of both GTD and Master Points reduces the time requirements of this kind of analysis. To validate the new approach, several reflectors and the effects on the radiation pattern caused by shifting the feed and introducing different obstacles have been considered concerning both simple and complex geometries. The results of these analyses have been compared with the Method of Moments (MoM) results.

scholarly journals Superresolution Polarimetric ISAR Imaging Based on 2D CP-GTD Model

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Da-hai Dai ◽  
Jing-ke Zhang ◽  
Xue-song Wang ◽  
Shun-ping Xiao
Keyword(s):  
Real Data ◽  
Scattering Matrix ◽  
Geometrical Theory ◽  
Scattering Mechanism ◽  
New Approach ◽  
Scattering Centers ◽  
Isar Imaging ◽  
Geometrical Theory Of Diffraction ◽  
The One ◽  
Better Than

This paper presented a new approach to superresolution ISAR imaging based on a scattering model called coherent polarized geometrical theory of diffraction (CP-GTD) which is better matched to the physical scattering mechanism. The algorithm is a joint processing between polarization and superresolution essentially. It can also estimate the number, position, frequency dependence, span, and normalized scattering matrix of scattering centers instantaneously for each channel rather than the one which extracts parameters from each channel separately, and its performance is better than the latter because the fully polarized information is used. The superiority of the CP-GTD is verified by experiment results based on simulated and real data.

scholarly journals A New Method of Designing Circularly Symmetric Shaped Dual Reflector Antennas Using Distorted Conics

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Mohammad Asif Zaman ◽  
Md. Abdul Matin
Keyword(s):  
Differential Geometry ◽  
Geometrical Optics ◽  
New Method ◽  
Geometrical Theory ◽  
Uniform Illumination ◽  
Reflector Antennas ◽  
Reflector Surface ◽  
Reflector System ◽  
Geometrical Theory Of Diffraction ◽  
Main Reflector

A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of the shaped subreflector is expressed using a new set of equations employing differential geometry. The proposed equations require only a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO) based method is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed method, a shaped Cassegrain dual reflector system is designed. The field scattered from the subreflector is calculated using uniform geometrical theory of diffraction (UTD). Finally, a numerical example is provided showing how a shaped subreflector produces more uniform illumination over the main reflector aperture compared to an unshaped subreflector.

scholarly journals Advances in hybrid finite element – boundary integral – multilevel fast multipole – uniform geometrical theory of diffraction method

2007 ◽  
Vol 5 ◽  
pp. 101-106
Author(s):  
A. Tzoulis ◽  
T. F. Eibert
Keyword(s):  
Finite Element ◽  
Electromagnetic Coupling ◽  
Near Field ◽  
Diffraction Method ◽  
Linear Interpolation ◽  
Boundary Integral ◽  
Geometrical Theory ◽  
Fast Multipole ◽  
Geometrical Theory Of Diffraction ◽  
Element Boundary

Abstract. Numerical modeling of problems including composite metallic/dielectric objects with arbitrary shapes and electrically large conducting objects within a common environment is performed in an optimum way with the recently developed powerful hybrid numerical method, which combines the Finite Element Boundary Integral (FEBI) method and the Multilevel Fast Multipole Method (MLFMM) with the Uniform Geometrical Theory of Diffraction (UTD), giving full electromagnetic coupling between all involved objects. In this contribution, the hybrid FEBI-MLFMM-UTD method is extended to double diffracted fields on pairs of straight metallic edges, formulated with the hard and soft scalar diffraction coefficients of UTD. The diffraction points on each pair of edges are determined by an iterative three-dimensional parametric realization of the generalized Fermat's principle. The divergence factor of the double diffracted field is computed by multiplying the appropriate divergence factors of the single diffracted UTD fields on each edge for the particular case. Thereby, the ray caustic distance of the diffracted field at the second edge is determined by linear interpolation between the radii of curvature in the two principal planes of the incident astigmatic ray tube. Further, fast near-field computation in the postprocessing stage of the hybrid method is extended in each translation domain to ray optical contributions due to the presence of electrically large objects, according to the hybridization of MLFMM with UTD. Formulations and numerical results will be presented.

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