Eric Robinson’s PhD Proposal Review

“Techniques for the Modelling, Design, and Fabrication of Ultra-Wideband Dipole Arrays”
Abstract:

A novel set of techniques are proposed which advance the state of the art for the modelling, design, and fabrication of ultra-wideband dipole arrays. First, existing techniques and relevant topics in the field are introduced and summarized. These include equivalent circuit and Green’s Function models for the impedance of the infinite dipole array. Challenges for the realization of arrays are discussed, including finite array effects, common-mode effects, and the limitations of different fabrication techniques. Several relevant recent innovations by the author are presented to form the foundation of the proposed work.

First, a new lossy transmission line model for the infinite dipole array impedance is described which results in highly accurate predictions across wide bandwidths and for large scan angles. The accuracy of the model is demonstrated via comparisons to full-wave simulations, and the model is used to rapidly design a wide-scanning, ultra-wideband array to demonstrate its value. Next, a new technique developed by the author is described for physically realizing complex dipole array geometries with integrated dielectrics. A tightly-coupled array is achieved by 3D-printing an array of elements featuring internal through-cavities in the shape of the radiating elements. The internal surfaces of these cavities are then metallized via a copper deposition, producing an array of conductive elements within a dielectric shell, resulting in improved mechanical rigidity, improved scan performance, and increased inter-element capacitance for ultrawide bandwidth.

Building on these results, additional research is proposed for completion of the dissertation. First, the lossy transmission line model will be extended to other relevant cases, including the unbalanced feed-structure-fed dipole array and the hybrid slot-dipole array. Second, a new model will be implemented to describe the effects of surface waves on the active impedance of the tightly-coupled dipole array. Mitigating techniques will be proposed based on the results of this model, enabling the realization of finite arrays which better conform to the predicted performance of the infinite array. Finally, each of the aforementioned models and techniques will be leveraged towards the design and fabrication of a notional array for an imaging application, demonstrating their practical value for array design.

Committee:

Prof. Carey Rappaport (Advisor)

Prof. Josep Jornet
Prof. Edwin Marengo Fuentes

Dr. Ian McMichael