Lens structures from novel materials for fixed and steerable beams antenna systems at sub-THz range
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
IT115
Topic of the dissertation
Lens structures from novel materials for fixed and steerable beams antenna systems at sub-THz range
Doctoral candidate
Master of Science Mikko Kokkonen
Faculty and unit
University of Oulu Graduate School, Faculty of Information Technology and Electrical Engineering, Microelectronics
Subject of study
Electrical Engineering
Opponent
Associate professor Zachary Taylor, Aalto University
Custos
Docent Sami Myllymäki, University of Oulu
Lens structures from novel materials for fixed and steerable beams antenna systems at sub-THz range
In this thesis, the feasibility of four different composite materials as a lens to be integrated into an antenna at frequencies 110–170 GHz or 220–330 GHz was investigated. The investigated lens structures were based on two different ways of refracting the wave with the lens, refraction due to the surface shape and permittivity of the lens, and diffraction. The performance of the lenses was examined using simulation methods and measurements. The refraction-based lens sizes used were at most 30 mm in diameter and 49.5 mm high, and the diffraction-based lens size was 25×27×3 mm3.
Nanocellulose-glass composite, lithium molybdate oxide-glass composite, nanocellulosecoated silica foam, and silica-polymethyl methacrylate composite were investigated. The first two of the composites used are water soluble and could be prepared at room temperature. The water solubility can facilitate the recycling of lenses in the future, and manufacturing at room temperature significantly reduces the need for energy during manufacture. Silica foam coated with nanocellulose is almost 100% air and is suitable as a substrate for diffraction based lenses when the diffraction pattern is sputtered onto the surface of the foam.
The above-mentioned composites are environmentally friendly because they do not contain plastic. The silicon oxidepolymethyl methacrylate composite is a plastic composite, but the amount of plastic in it was reduced with silica so that the final composite contained ~20% silica and 80% plastics. The dielectric properties of the composites used in the work were as follows: relative permittivity 1.018–1.5 and loss tangent 3–40×10−4. In addition, the very low relative permittivity also resulted in very low reflection from the lens surface (reflectivity < 1%). Low reflectivity and a low loss tangent can be considered useful properties in lenses, because the electromagnetic wave propagating through the lens is only slightly weakened, i.e. the efficiency of the lenses is high.
Nanocellulose-glass composite, lithium molybdate oxide-glass composite, nanocellulosecoated silica foam, and silica-polymethyl methacrylate composite were investigated. The first two of the composites used are water soluble and could be prepared at room temperature. The water solubility can facilitate the recycling of lenses in the future, and manufacturing at room temperature significantly reduces the need for energy during manufacture. Silica foam coated with nanocellulose is almost 100% air and is suitable as a substrate for diffraction based lenses when the diffraction pattern is sputtered onto the surface of the foam.
The above-mentioned composites are environmentally friendly because they do not contain plastic. The silicon oxidepolymethyl methacrylate composite is a plastic composite, but the amount of plastic in it was reduced with silica so that the final composite contained ~20% silica and 80% plastics. The dielectric properties of the composites used in the work were as follows: relative permittivity 1.018–1.5 and loss tangent 3–40×10−4. In addition, the very low relative permittivity also resulted in very low reflection from the lens surface (reflectivity < 1%). Low reflectivity and a low loss tangent can be considered useful properties in lenses, because the electromagnetic wave propagating through the lens is only slightly weakened, i.e. the efficiency of the lenses is high.
Last updated: 16.2.2024