Multiple Electromagnetic Scattering within and Electrical Characterization of 3D-Printed Dielectrics

Open Access
- Author:
- Hu, Hanxiong
- Graduate Program:
- Electrical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 16, 2021
- Committee Members:
- Nicholas Meisel, Outside Unit & Field Member
Timothy Simpson, Outside Field Member
Sven Bilén, Chair & Dissertation Advisor
Julio Urbina, Major Field Member
Xingjie Ni, Major Field Member
Kultegin Aydin, Program Head/Chair - Keywords:
- electromagnetic scattering
additive manufacturing
microwave components
dielectric characterization - Abstract:
- Additive manufacturing (AM) is an increasingly popular method for manufacturing antennas and other microwave components to achieve rapid prototyping and design flexibility at a low cost. Embedding AM antenna elements or radio-frequency (RF) and microwave components within structures will further reduce weight and improve system integration, e.g., embedding a tracking antenna within the wing of an unmanned aerial vehicle. For the technology to be universally adopted for direct product manufacturing with AM technologies, a better understanding of the AM material properties is required. An analytical model was developed to simulated the propagation of electromagnetic wave in a dielectric substrate with an air--dielectric interface and a cylindrical air-filled cavity. The scattering interactions were described using expansion of cylindrical wave functions, and solved using the tangential electromagnetic field components of the boundary conditions. Multiple scattering between the air--dielectric interface and the cylindrical air-filled cavity were then simplified by mirroring the cylindrical air-filled cavity, and then transformed with the use of Hankel functions, summing the multiple scattering contributions, and recalculating the scattering. The surface electromagnetic fields were acquired and compared with results from FEKO to demonstrate the relevance of the scattering method. The two-microstrip-line method and the two-port transmission line method with waveguides were used to measure the permittivity of AM and synthetic materials for fabrication RF components. The results of the two methods showed they are qualitatively accurate when compared with reference values of bulk commercial substrates, and can be used to acquire permittivity of AM-built and synthetic materials for AM microwave components. By taking advantages of AM dielectric substrates, how infill density and infill pattern impact the permittivity of AM dielectric substrates were investigated. A linear relationship between infill density of the rectangular pattern and the substrate permittivity was found. The permittivity data were applied to the design of a rectangular patch antenna for use in 2.5-GHz WiMAX band. The fabricated antenna with AM showed good agreement with simulation results, which was characterized using a vector network analyzer. In addition, power dividers and filters were designed and fabricated by printing silver nanoparticle ink on a polyimide substrate, an AM thermoplastic polyurethane (TPU), and a synthetic material substrate. The theory and method developed for characterizing AM dielectric substrates can be flexibly applied to the design and fabrication of AM microwave components. The goal of the research was to characterize AM material and utilize the measured permittivity in the design of AM microwave components.