Near field coupling between elements of a finite planar array of circular apertures

The mutual admittance between two waveguide-fed apertures radiating into a multilayered region is expressed as a double integral of a combination of the Fourier transforms of the respective aperture electric fields and the solutions to a set of transformed wave equations for the layered region. The result is an expression which is stationary about variations in the assumed aperture electric field distributions. The special case of two circular apertures whose electric field distributions are assumed to be the same as the TE_mn and TM_mn circular waveguide modes is analyzed in detail. In this case, the admittance expression can be reduced to a single integral which simplifies the numerical calculation. A computer program was written which can include up to four external layers, two of which may be inhomogeneous normal to the aperture plane. Numerical results for the mutual coupling between two circular apertures with TE₁₁ mode excitation agree very well with measurements for both free space and one homogeneous dielectric layer. Numerical results are compared with measurements of two circular apertures in a 12 inch by 24 inch flat plate for various combinations of frequency, polarization, and spacing in order to verify all aspects of the solution. It was noted that in some cases, the diffractions from the edges of the ground plane caused some appreciable variations in the measured data, although the measurements in all cases tended to scatter about the calculated values. A numerical study was performed in order to determine the effect of higher order TE_mn and TM_mn modes upon the TE₁₁ mode coupling of two circular apertures radiating into free space. The only noticeable effect was a change in the phase of the coupling coefficient when the TM₁₁ mode was included in the calculations. A study of the effects of array size upon the performance of a triangular grid arrangement of circular apertures indicated that the elements near the center of a large phased array have similar radiation characteristics to those of an infinite array, except near the scan angle at which the"blind spot" occurs. At this angle, the reflection coefficient of the center element of the finite array exhibited a sharp peak, but not total reflection as in the infinite array. Also major differences were observed between the reflection coefficients of the center element and the edge elements of the finite array as a function of beam scan.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Electrical Engineering

Department dc:contributor.department

Electrical Engineering

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1972

Author dc:creator

• Bailey, Marion Crawford

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/94527

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/94527