Thesis Abstracts 2006
Research and Graduate Studies Electrical and Computer Engineering
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Investigation and Application of the Talbot Effect in the Millimeter-Wave Band
By: Mr. Michael Keller (PhD candidate)
Supervisor: Dr. YMM Antar and Dr. J. Shaker
Abstract
The Talbot effect is a near-field diffraction and interference optical phenomenon that was reported in 1836 by H.F. Talbot. The phenomenon is observed when a periodic grating is illuminated by a plane wave of monochromatic electromagnetic energy. At certain longitudinal periodic “Talbot distances” beyond the structure, the field distribution resembles the original grating in form and contrast; hence, the effect is often referred to as “lensless self-imaging”. Other interesting phenomena associated with the Talbot effect are the image multiplication and the image shifting that occur at fractions of the Talbot distance between the periodic object and the image plane. The Talbot effect has been applied to perform various functions such as: electron microscopy; periodic image synthesis; and, most significantly, optical device array illumination. The optical device illuminators are also known as Talbot Array Illuminators (TAILs), and presently they find application in optical interconnections and digital optical computing architectures. In the microwave spectrum, the self-imaging concept has been offered as an analogy to explain the operation of a waveguide spatial power combiner; however, there have been neither true observations nor applications of the Talbot effect in the microwave or millimeter-wave bands.
This thesis explores the Talbot effect at millimeter-wave frequencies, and experimentally reveals the details of the phenomenon beyond various periodic phase and amplitude gratings illuminated by a Gaussian beam. In addition to the scalar approach used in optics, several different and unique vectorial analysis methods are introduced in order to accurately predict the image formation. Furthermore, this research introduces some novel grating configurations that exploit the Talbot effect in the microwave and millimeter-wave spectrum in order to perform tasks such as free space power splitting and combining. Compared to other approaches, spatial power splitting and combining using the Talbot effect holds the potential of high efficiency and high power handling capability. As such, several applications that take advantage of this concept are investigated. For instance, a novel spatial amplifier that can be adapted to perform antenna functions, and several other unique antenna configurations that result in compact high effective irradiated power antenna configurations are investigated.
