Date of Award

Fall 2022

Embargo Period

12-14-2023

Access Type

Dissertation - Open Access

Degree Name

Doctor of Philosophy in Electrical Engineering & Computer Science

Department

Electrical Engineering and Computer Science

Committee Chair

Eduardo A. Rojas-Nastrucci

First Committee Member

M. Ilhan Akbas

Second Committee Member

Radu F. Babiceanu

Third Committee Member

Daewon Kim

Fourth Committee Member

Marwan Al-Haik

Abstract

As traditional monitoring data sensors in high temperature environments such as gas turbine engines and aerospace applications are being replaced by wireless equivalents in recent years, there is a need for low-cost, low-time, and low-infrastructure alternatives to further push the state of the art. In this work, two aspects of high temperature materials in the above context are explored: (a) the development of advanced manufacturing techniques for high temperature materials that is lowcost, low-time, and low-infrastructure, and (b) the development of material characterization techniques that can be integrated with the manufacturing processes of high temperature materials. Additive manufacturing has been known to be an alternative for low-cost and rapid prototyping manufacturing solution but its usage for high temperature materials is relatively recent. Unlike fused deposition modelling (FDM) and inkjet printing (IJP) for thermoplastics and conductive pastes respectively, high temperature materials, dominated by ceramics, are typically unavailable in the forms that are compatible with the methods above. Therefore, microdispensing, nanoparticle jetting, and digital light processing (DLP) are emerging solutions to create AM ceramic structures. Furthermore, high temperature materials typically require additional processing steps, such as sintering, to finalize the structures created, unlike their low temperature equivalents. In this work, micro-dispensing and DLP of dielectric pastes on a known substrate is used to create a multilayer configuration of a coplanar waveguide (CPW).

Performing RF probing on the CPW structure and measuring its S-parameters allows for the determination of the permittivity by extracting the propagation characteristics and then performing an analysis with conformal mapping of the multilayer CPW structure. Furthermore, by creating air pocket slots in the CPW structure, the loss tangent of the material can be determined by extracting the attenuation constant at various depths. To verify this methodology, a mathematical model is developed for CPW structures with air pocket slots, supported by finite element method (FEM) simulations showing less than 5 percent error between the mathematical model and simulations. A new metric has also been introduced namely the partial derivatives of the attenuation and phase constants with respect to slot depths, to show that the determination of loss tangent is possible and to further enhance the permittivity extraction technique up to 20 GHz. The manufacturing and characterization techniques are then applied to LTCC ceramic pastes to design an additive manufactured antenna for mm-wave applications.

Besides micro-dispensing of raw ceramic pastes, microwave and mm-wave sensors and antennas can also be created through 3-D laser machining using a planar printed circuit board (PCB) manufacturing tool. In this work, a pressure sensor based on evanescent-mode resonance is demonstrated using this technique. This is demonstrated by first developing a study of laser etching profile, measured by a profilometer, and then applying the appropriate machining parameters to create the final structure. The manufactured wireless sensor is then tested, and its performance is measured up to the temperature requirements of 1700 °C using a high temperature measuring setup. Measurements indicate that the manufactured sensor may operate from 25 °C to 1700 °C, sensing pressures from 0 psi to 163 psi with resonant responses varying from 6.33 GHz to 6.7 GHz.

Additional Files
GS9_Acceptance_Yu.pdf (392 kB)
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