Design and fabrication of helical antennas with non-uniform cross-section wire via metal additive manufacturing

• Ano de defesa: 0024
• Autor(a) principal: Martins, Nícholas Fonseca
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Antennas (Electronics); Microwave antennas; Microwave communication systems
• Link de acesso: https://hdl.handle.net/11449/255741

This dissertation presents a study on helical antennas, introducing a new mathematical formulation for representing the helix, in which the diameter, spacing, and cross-section of the metal wire are non-uniform. It is demonstrated how these modifications, combined with optimization techniques, can be used to improve the electromagnetic performance of designed antennas. Precisely defining the transition region between the helix and the central feeding point, a thicker wire was strategically employed at the base to enhance both the antenna’s operational bandwidth and mechanical strength, eliminating the need for additional support structures. The wire diameter was linearly reduced towards the top of the helix to improve radiation characteristics. To address the manufacturing challenges presented by the complex geometries of non-uniform helical antennas, the additive metal manufacturing process was employed. Maraging steel was chosen for its ability to withstand severe environmental conditions and temperature fluctuations without experiencing significant deformations, distinguishing it from polymer alternatives. The proposed formulation was explored using three models tailored for the X-band (8 GHz to 12 GHz): Model I) A standard helical antenna featuring uniform diameter and helix spacing; Model II) a helical antenna with non-uniform diameter and helix spacing; and Model III) a helical antenna with non-uniform diameter, cross-section, and helix spacing. The findings illustrate that the helical antenna utilizing a tapered cross-section wire (thicker at the base and thinner at the tip) exhibits significantly superior performance compared to the control models. Specifically, we present an eight-turn helical antenna that attained a measured reflection coefficient below −10dB and an axial ratio of less than 1dB across the X-band, with a peak realized gain in right-hand circular polarization (RHCP) of 10.8dBic.