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High-frequency asymptotic methods for analyzing the EM scattering by open-ended waveguide cavitiesFour high-frequency methods are described for analyzing the electromagnetic (EM) scattering by electrically large open-ended cavities. They are: (1) a hybrid combination of waveguide modal analysis and high-frequency asymptotics, (2) geometrical optics (GO) ray shooting, (3) Gaussian beam (GB) shooting, and (4) the generalized ray expansion (GRE) method. The hybrid modal method gives very accurate results but is limited to cavities which are made up of sections of uniform waveguides for which the modal fields are known. The GO ray shooting method can be applied to much more arbitrary cavity geometries and can handle absorber treated interior walls, but it generally only predicts the major trends of the RCS pattern and not the details. Also, a very large number of rays need to be tracked for each new incidence angle. Like the GO ray shooting method, the GB shooting method can handle more arbitrary cavities, but it is much more efficient and generally more accurate than the GO method because it includes the fields diffracted by the rim at the open end which enter the cavity. However, due to beam divergence effects the GB method is limited to cavities which are not very long compared to their width. The GRE method overcomes the length-to-width limitation of the GB method by replacing the GB's with GO ray tubes which are launched in the same manner as the GB's to include the interior rim diffracted field. This method gives good accuracy and is generally more efficient than the GO method, but a large number of ray tubes needs to be tracked.
Document ID
19900006787
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Burkholder, R. J.
(Ohio State Univ. Columbus, OH, United States)
Pathak, P. H.
(Ohio State Univ. Columbus, OH, United States)
Date Acquired
September 6, 2013
Publication Date
September 1, 1989
Subject Category
Communications And Radar
Report/Patent Number
ESL-TR-719630-3
NASA-CR-186244
NAS 1.26:186244
Accession Number
90N16103
Funding Number(s)
CONTRACT_GRANT: NAG3-476
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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