Date of Award
Doctor of Philosophy
Electrical and Computer Engineering
The antenna is an integral part of any wireless communication system that is primarily used for transmitting and receiving radio frequency signals. There are various types of antennas which can be characterized by its electromagnetic performance such as frequency bandwidth and its geometrical shape most useful for particular applications. Spiral antennas describe one set of antennas which find extensive application in satellite communications. Because of the complex geometry of the spiral antenna, it can be arduous to fabricate in practice. Also, due to the higher input impedance of the spiral antenna compared to conventional transmission line impedance, concern about external impedance matching is an issue. This research mainly focuses on three major factors: First, employing 3D-printing technology to achieve rapid prototyping of different types of spiral antennas. Second, introducing a flat-strip form of the spiral arm instead of circular wire to achieve impedance matching without using an external impedance matching network. Finally, using conductive paint as a separate approach along with a copper strip for radiating part to further ease prototyping. The first antenna is a compact 1.3 turns helical antenna with a height of 0.35λ0 that operates in the 1.8 GHz to 4 GHz frequency range. The strip width is 15 mm and both copper strip and conductive paints are used for radiating elements. The second antenna is a single-arm semi-ellipsoidal helical antenna. It is fabricated and tested for circular polarization in the frequency range of 2 GHz to 4 GHz. Both copper strips and conductive paint as radiating parts are used here. The base radius, strip width, and height of the semi-ellipsoidal helical antenna are 0.175λ0 (25 mm), 4 mm, and 0.35λ0 (50 mm) respectively. The third antenna is a single-arm strip-based conical log spiral that is both fabricated and tested. The lower radius and height of the truncated cone are 25.15 mm and 121.1 mm respectively which works in the frequency range of 1.7 GHz to 3.5 GHz. The fourth antenna is a low-profile hemispherical helical antenna with a radius of the hemisphere of 23 mm, a strip width of 7 mm, and a wire diameter of 4.50 mm. This antenna operates between 2.72 GHz to 3.87 GHz. Simulations for all antennas are carried out using electromagnetic simulation software CST Microwave Studio. The Sindoh 3D WOX printer with polylactic acid (PLA) material is used for 3D printing of the supportive structure. Copper wire, foil tape, and conductive paints are used as the radiating part of all the antennas. An Agilent E8362C performance network analyzer (PNA) and a spherical near-field anechoic chamber are used for measuring input impedance, radiation patterns, and other parameters of the antenna. Good agreement between simulated and measured results for all the antennas was found. Finally, introducing additive manufacturing (3D printing) for prototyping the non-planar strip-based spiral antennas was successful.
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