Browsing by Author "Abdullahi, Qassim Suleiman"

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Study of thermochromic nature of VO2 for reconfigurable frequency selection applications
(Heriot-Watt University, 2022-12) Abdullahi, Qassim Suleiman; Anagnostou, Doctor Dimitris E.; Goussetis, Doctor George
The goal of this project is to investigate the use of vanadium dioxide in reconfigurable microwave devices such as antennas or filters. The second phase would see the creation of a more concrete application. The ability of vanadium dioxide (VO2) to change its structure above a certain temperature is of particular interest. Under 68°C, VO2 behaves like a dielectric, but when it reaches and exceeds that temperature, it behaves like a metal. With this in mind, we wanted to demonstrate the possibility of creating a reconfigurable FSS for spatial filtering by selectively heating the VO2 sample's surface area. A laser was used to select which area of the sample to heat: by shaping the beam, we were able to illuminate, and thus heat, only specific areas. This dissertation also describes the use of the time-resolved microwave conductivity (TRMC) technique to characterise vanadium dioxide to design these FSS images projected on the VO2 surface. We show that TRMC is a versatile technique for determining the electromagnetic material properties and conductivity of VO2 compounds. This was used to compare the behaviour of several VO2 samples of varying thicknesses and fabrication technologies.