Title:  Flexible Electronics for RF and mmWave Applications

Committee:

Dr. Madhavan Swaminathan, ECE, Chair, Advisor

Dr. Saibal Mukhopadhyay, ECE

Dr. Suresh Sitaraman, ECE

Dr. Andrew Peterson, ECE

Dr. Manos Tentzeris, ECE

Abstract: Due to the increasing demand for wearable and flexible devices, Flexible Hybrid Electronics (FHE) has seen a rapid increase into further development. Ultimately, the goal for FHE is to maximize the mechanical flexibility (bending, stretching, and twisting) of a device while maintaining or improving the electrical performance, miniaturizing individual components, and increasing system level integration. One additional consideration required for designing flexible and wearable electronics is accounting for the impact of flexible phenomena on different components. This is noticeable when comparing the performance of a coplanar waveguide (CPW) against an antenna while both are bent a small amount compared to their lengths. For a coplanar waveguide, minimal change in the S Parameters was found whereas for an antenna, the resonant frequency may shift given the architecture of the antenna. Therefore, proper modeling and model to hardware correlation are required when designing for FHE systems. First, this work focuses on completing model to hardware correlation for different components such as microstrip transmission lines and planar inductors while these components undergo bending. The next step is to characterize and use a lower loss stack-up for high frequency flexible applications. In this case, ultra-thin flexible glass was chosen and was characterized electrically (dielectric constant and dielectric loss tangent) up to 110 GHz and mechanically (determining when mechanical failure occurs while undergoing bending). After completing the ultra-thin, flexible glass characterization, a patch antenna array was designed, fabricated, and measured for 24 GHz Automotive Doppler Radar. This array underwent both flat and bending measurements for both the S Parameters and radiation pattern to determine the impact of the bending on the initial, flat performance. For the S Parameters, minimal change was found while the antenna array underwent bending, but noticeable change in the radiation pattern was found. After completing the antenna array measurements, an Automotive Doppler Radar was designed and fabricated onto the ultra-thin glass. This radar includes a Quadrature Hybrid coupler and a passive mixer to complete the doppler radar. Finally, the thesis also discussed the design requirements of a 77 GHz antenna array for automotive applications, the current standard for automotive radars.