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Title: Investigation of optically tunable microwave circuits and antennas
Author: Gamlath, Christy D.
ISNI:       0000 0004 5991 371X
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2016
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Much of the recent work on optically tunable methods have relied on the use of optically tunable switches. Although these methods provide effective tuning of microwave devices particularly in the lower microwave band, there is the fundamental limitation that the position of the switch is always fixed which limits the capability for tuning. Several previous investigations have looked at using spatial variations in the illumination pattern. These have always required the use of high power bulky laser sources which cannot be integrated into the microwave device. The recent advances in semiconductor laser technology allow both intensity and spatial profiles of illumination to be varied dynamically at speeds of up to fractions of a microsecond while maintaining a compact form factor. This opens up a new area for investigation in optically tunable microwave devices which provides the motivation for the current work. The primary focus of the project is to investigate new designs of optically tunable microwave circuits arid antennas that can take advantage of the spatial and intensity variations of the illumination profile and at the same time maintain a small form factor. In order to achieve this a significant portion of work was required to characterize the loss mechanisms taking place inside the optically illuminated region at high frequencies. This material is presented and is followed by investigations into new types of tunable microwave devices. The significant contributions of this work are contained in Chapters 4,5, and 6. The characterization of optically illuminated plasmas presented in current literature is limited to small regions of illumination. Chapter 4 extends this microwave characterization to longer lengths of illumination and also to higher microwave frequencies. The first part of Chapter 5 presents new techniques for tunable loads based on illumination pattern variations. The second part presents a novel technique for producing variable true time delay phase shifts which has not been demonstrated previously. Chapter 6 shows several new methods for designing tuneable microwave antennas based on integrating light sources within the microwave structure. This work has contributed to expanding the current literature on optically tunable devices. The fundamental focus has been on the use of miniature light sources since these can be integrated into the structure of the microwave device to form a compact tunable package. Several new ideas have been presented based on this concept.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available