Electrical and Computer Engineering ETDs

Publication Date

8-27-2009

Abstract

This work deals with the design and bench test of rectangular waveguide narrow-wall longitudinal-aperture antenna arrays for high power applications. The best narrow-wall longitudinal-aperture array designs in the work are called the double-narrow-wall-slot-HPB-array and the double-split-waveguide-HPB-array. The double-narrow-wall-slot-HPB-array (double-split-waveguide-HPB-array) consists of two identical narrow-wall-slot-HPB-arrays (split-waveguide-HPB-arrays) with a common broad wall. All elements of the split-waveguide-HPB-array are identical and are called H-plane-bend-radiators (HPB-radiators). An HPB-radiator is an H-plane bend terminating in a radiating aperture with the narrow dimension of the waveguide flaring out. Optimizing the HPB-radiators performance involves designing its aperture dimensions and the function that determines the H-plane taper to minimize the reflected power into the feed-waveguide while maintaining a half sine wave aperture electric field (E-field) distribution. Once the optimal HPB-radiator is designed, the design of the split-waveguide-HPB-array is similar to designing a uniform linear array. There is minimal mutual coupling between the elements through the waveguide, and for design purposes, external coupling between the elements can be ignored. The first four elements of the narrow-wall-slot-HPB-array are longitudinal-slots in the narrow wall of a rectangular waveguide, and the last element is an HPB-radiator with the same optimal performance criteria as that of the split-waveguide-HPB-array. The narrow-wall-slot-HPB-array is designed by a combination of computational and microwave network analysis techniques. First, computational analysis of the individual slots is performed separately. In the next step, each longitudinal-slot in the narrow wall of the guide is reduced to a lossy two port microwave network whose S-parameters have been obtained from the computational analysis; the loss in the network represents the power radiated by the slot. Finally, microwave network analysis is used to design a uniform linear array with a low reflected power into the feed-waveguide. The primary advantage of the split-waveguide-HPB-array over the narrow-wall-slot-HPB-array is its ability to beam steer since the inputs to its elements can be controlled separately. Since the structures are used for high power applications, the HPB-radiator's H-plane taper function needs to be smooth without any sharp corners. Its design procedure, using just computational or analytical methods, was intractable. The design procedure is therefore formalized using a novel approach, which processes the computational analysis data using iterative search algorithms. This approach is made possible by mapping a design output variable that is computationally intensive, to another that requires much less computational time. This approach is based on a hypothesis that is called the 'dimensional offset hypothesis'. The behavior of narrow-wall longitudinal-slots with dimensions comparable to a free-space wavelength is also characterized. The similarities they possess with wire radiators are presented. The experimental results validate the theoretical analysis results for the design of an HPB-radiator and from the microwave network analysis. The power handling capability analysis for the double-narrow-wall-slot-HPB-array and the double-split-waveguide-HPB-array is also presented.'

Keywords

Antenna arrays., Aperture antennas., Wave guides.

Sponsors

University of New Mexico

Document Type

Dissertation

Language

English

Degree Name

Electrical Engineering

Level of Degree

Doctoral

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Baum, Carl

Second Committee Member

Schamiloglu, Edl

Third Committee Member

Embid, Pedro

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