Date of Award

Spring 1-1-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical, Computer & Energy Engineering

First Advisor

Dejan S. Filipovic

Second Advisor

Maxim Ignatenko

Third Advisor

Neill Kefauver

Fourth Advisor

James B. Mead

Abstract

With any reflecting or refracting structure, such as a parabolic reflector or lens antenna, the knowledge of the focal point is critical in the design as it determines the point at which a feeding signal should originate for proper operation. Spherically symmetrical lenses have a distinct advantage over other structure types in that there exists an infinite number of focal points surrounding the lens. Due to this feature, a spherical lens can remain in a fixed position while a beam can be steered to any direction by movement of the feed only. Unlike phased arrays that beam-steer electronically, a spherical lens exhibits no beam deterioration at wide angles. The lens that accomplishes this is in practice called the Luneburg lens which has been studied since the 1940s.

Due to the electromechanical properties of the horn antenna, it is often used to feed the above mentioned configurations. In the focusing of any feed antenna, its phase center is an approximate point in space that should be coincident with a reflector or lens’s focal point to minimize phase error over the radiating aperture. Although this is often easily accomplished over a narrow bandwidth, over wide bandwidths some antennas have phase centers that vary significantly, making their focusing a challenge.

This thesis seeks to explain the problem with focusing a Luneburg lens with a canonical horn antenna and offers a modified horn design that remains nearly focused over a frequency band of 18 – 45 GHz. In addition to simulating the feed / lens configurations, the lens and feed horn will be fabricated and mounted for far field measurements to be taken in an anechoic antenna range. A final feed design will be implemented in an array configuration with the Luneburg lens, capable of transmitting and receiving multiple beams without requiring any moving parts or complex electronic beam-forming networks. As a tradeoff, a separate receiver or switching network is required to accommodate each feed antenna. This aspect of the system, however, is outside the scope of research for this thesis.

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