Miroslav JolerProfessor, University of Rijeka, Croatia
Speech Title: On Characterization of Dielectric Properties of Non-standard Materials Using a Low-cost Resonator Circuit
Abstract: In design of wearable electronics, engineers face a task of having to sufficiently accurately determine dielectric properties of non-standard substrate materials, such as various fabrics, in order to successfully design a desired circuit, e.g. a textile antenna or a substrate-integrated waveguide. It is known that determination of dielectric properties is a subtle task, even nowadays, when sophisticated hardware and software are available, due to sensitivity of the measurement on various factors that are involved in the process. Depending on the type of the material sample to be characterized, several measurement methods are widely known, each with distinctive traits. It turns out, however, that even the most advanced and costly measurement apparatuses today can offer only a modest accuracy, followed by disclaimers regarding the measurements conditions. Given that fact, a viable alternative can be to design our own, low-cost, measurement setup that could provide a satisfactory accuracy for practical purposes. One such approach is based on the resonator circuit. Although the topic has been tackled in various papers, one will hardly find a complete or transparent and detailed measurement procedure that is part of the public domain, which cognition spontaneously lead us to revisit the topic. In this talk, an overview of the measurement principle of a ring resonator structure will be introduced and some previously defined approaches commented on. Dependence of the results on the characteristics of the sample and the resonator will be discussed based on full-wave numerical solver simulations and measurements. Finally, a hybrid approach, as a combination of an analytical model and sample measurement, will be presented for determination of relative permittivity and loss tangent of a material sample.
Biography: Prof. Miroslav Joler received his B.S. degree in electrical engineering from the University of Zagreb, Croatia, in 1996, and his M.S. and Ph.D. degrees in electrical engineering from the University of New Mexico, Albuquerque, NM, USA, in 2001 and 2006, respectively. In 2006, he was a postdoctoral research associate with Portland State University, Portland, OR, USA. In 2007, he joined the University of Rijeka, Croatia, where he has founded a Wireless Communications Lab, and served as Chair of Computer Engineering Department, amongst other duties. His industry experience includes a position of an RF engineer with Croatian Radio and Television from 1996 to 1999. He has published in prominent scientific journals and served as session (co)chair, and technical program committee member at international conferences. He is an Editorial Board Member of two international scientific publishers. In 2017, he was elected Associate to Croatian Academy of Engineering. His current research interests include development of smart clothing, wearable and adaptive antennas, biomedical applications of electromagnetics and urban models of wireless power transfer.