Date of Award

Fall 12-15-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

Advisor

Mauricio Pereira da Cunha

Second Committee Member

Nuri Emanetoglu

Third Committee Member

Donald Hummels

Abstract

With increasing demand for harsh environment (HE) wireless sensor applications, the need for antennas capable of operating under temperatures up to 1000° C and under corrosive and erosive environments also increases. These environments place severe survivability, stability, and performance demands on antennas designed and fabricated to operate in such conditions.

This work focuses on the design, fabrication, simulation and performance investigation of a compact (~1/25th to 1/10th of a wavelength) combined helical and microstrip antenna design operating as a normal mode helical antenna structure (NMHAS) around 300MHz. The ground plane of the microstrip line also serves as a ground plane to the helical structure radiating element. It was found that varying the length of the microstrip line and associated ground plane from 0.5 inch to 3 inches resulted in the decrease of the measured NMHAS operating frequency and also affected the reactive response of the antenna. A compact 1:1 balun transformer was used to partially decouple the integrated NMHAS from the external sheath of the coaxial cable connected to a vector network analyzer, used to measure the NMHAS scattering (S) parameters. The balun parasitics network was modeled and simulated with the aid of ADS software. The NMHAS S11 and corresponding impedance response were also simulated on two different platforms, ANSYS-HFSS and WIPL-D Pro, and compared to the measured frequency responses. The effect of the helix orientation with respect to the microstrip line plane on the response of NMHAS was also measured and found to have an impact in the antenna impedance response. Finally, the transmission loss of two similar NMHASs placed at different distances apart from each other was measured with and without the presence of an additional matching network. It was found that at the measured distances between 10 inch and 44 inches, the two NMHASs interact, thus affecting each other’s impedance when compared to each NMHAS structure operating alone. This work confirmed that the NMHAS serves as a viable antenna structure for HE wireless sensor applications, owing to its utilization of air as a dielectric, compact design, and ease of integration.

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