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4-Port Microstrip planar resonator for multiband microwave material characterization applications

Anja Skrivervik Favre

Planar microstrip resonators suitable for material characterization application are presented in this paper. The prototype consists of three resonators fed through four ports in a planar dielectric substrate without any additional resonators. The resonators are working in different frequency regions making it suitable for resonant based characterization at different frequencies using a single prototype. In this proposed work, the overall dimension of the prototype is 100mm x 50mm when fabricated in a 1.6mm thick FR4 epoxy substrate of dielectric constant 4.4 and loss tangent 0.02. The three resonators are operating within their fundamental mode at 900MHz, 1.8GHz and 2.4GHz respectively. The analysis in this work is carried out on the fundamental electrical mode for all the three resonators, but is similar for the higher order modes. The prototype is highly compact and low cost compared to the conventional cavity based resonant characterization techniques.

IEEE2022

Theoretical Efficiency and Dosimetry of Buffered On-body Transmitter Antennas for Wireless Powering of In-body Devices

Denys Nikolayev, Anja Skrivervik Favre

The viable and safe application of wireless power transfer for powering bioelectronic implants requires understanding the wave propagation in heterogeneous and dispersive media, the electromagnetic exposure assessment, and the optimum design of the system parameters to achieve a trade-off between efficiency and specific absorption rate levels. Therefore, based on the case study of a wirelessly charged deep-implanted pacemaker, a parametric analysis on the transmitter dimensions and electromagnetic properties is carried out to achieve such a trade-off. The results show that the system reaches the maximum efficiency without increasing SAR levels when the transmitter is composed of an electric source, an air-like substrate, and a superstrate matched to the wave impedance in the skin with a thickness of half the wavelength in this medium. Furthermore, this configuration is compared to a magnetic counterpart, and the reasons for its suboptimal performance are investigated in terms of near-field, reflection, and attenuation losses.

IEEE2022

On the Maximum Power Density of Implanted Antennas within Simplified Body Phantoms

Mingxiang Gao, Zvonimir Sipus, Anja Skrivervik Favre

With the application requirements of wireless technology in implantable bioelectronics, knowledge of the fundamental limits for implanted antennas becomes critical. In this work, we investigated the variation of maximum power density within simplified body phantoms, caused by changes in the operating frequency, implantation depth, body phantom radius, and source size. Both spherical and planar body models are studied, and the corresponding results are compared to an efficient approximation method. The summarized results are used to derive design rules and can be used as benchmarks for the design of most implanted antennas, especially for shallow implants.

IEEE2022