Accession Number : AD0689188

Title :   SCATTERING BY A SPHERICAL SHELL WITH A CIRCULAR APERTURE,

Corporate Author : MICHIGAN UNIV ANN ARBOR RADIATION LAB

Personal Author(s) : Chang,Seichoong ; Senior,Thomas B. A.

Report Date : APR 1969

Pagination or Media Count : 149

Abstract : The electromagnetic scattering behavior of a spherical shell with a circular aperture was studied. The shell was assumed to be perfectly conducting and infinitesimally thin, and was illuminated by a plane wave symmetrically incident upon the aperture. The application of the method of least square error, as well as of a modified version is fully discussed. The modification consists of the separating out of the appropriate surface field behavior near to the edge of the aperture, and was carried out to overcome the slow convergence and marginal accuracy of the original approach. The marked improvement provided by the modification is clearly evident. The numerical study was limited to the frequency range corresponding to 0.8Lor=kaLor=4.85, where a is the radius of the spherical shell, and numerical values of the backscattering cross sections for the aperture angle theta sub o=30 degrees and 90 degrees, as well as for the tangetial field components over the boundary surface for theta sub 0=30 degrees, are presented. To verify these results and to obtain more physical insight into the scattering behavior, experimental measurements of the backscattering cross sections for theta sub o=15, 30, 45, 60 and 90 degrees, and of the current components for theta sub o=30 degree, are obtained using two sets of spherical shell models. It is observed that a spherical shell with aperture-on incidence has, in general, a higher backscattering cross section than a solid sphere except at values of ka near to the cavity resonances, where marked reductions occur. A comparison of the numerical and experimental results is made. (Author)

Descriptors :   (*RADOMES, RADAR CROSS SECTIONS), (*ELECTROMAGNETIC RADIATION, SCATTERING), SPHERES, SHELLS(STRUCTURAL FORMS), NUMERICAL ANALYSIS

Subject Categories : Active & Passive Radar Detection & Equipment
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE