Realization of a Portable Semi-Shielded Chamber for Evaluation of Fat-Intrabody Communication.

In this work, a customized portable semi-shielded chamber for torso phantoms to evaluate fat-intrabody communication (Fat-IBC) is presented. Fat-IBC is a technology where human fat tissue is used for microwave communication with intrabody medical devices. The potential clinical applications are vast including central nervous system (brain and spine) communication, cardiovascular disease monitoring and metabolic disorder control. However, validating this technology needs assurance that the signal leakage through undesired paths, particularly surface waves and reflections, does not occur. To solve this issue, an effective technique involving a modified design of a semi-shielded chamber is presented. The crosssection of the torso phantoms is about 25 cm x 35 cm and the height about 20 cm. As specified by ISO 3745:2012, the maximum object volume that can be measured in a chamber is 5% of the chamber's internal net volume. Therefore, the dimensions of the semi-shielded chamber was set to 100 cm x 60 cm x 60 cm. The semi-shielded chamber was constructed out of a wooden crate, covered on the inside with microwave absorbers and with thin aluminum sheets on the outside. The experimental evaluation of the semi-shielded chamber was validated according to standards such as EN 50147-1:1996, IEC 61000-4-3:2020, and IEC CISPR 16-1-4:2019. The torso phantom was positioned at the center of the chamber, with a separation wall to ensure signal transmission solely through the phantoms interior and not its surface or chamber walls. The separation wall can be modified either to be conformal to the phantom sample or serve as a solid partition dividing the chamber into two separate volumes for performance measurement. The separation wall was found to have a shielding attenuation of 30 dB to 60 dB for frequencies between 0.7 GHz and 18 GHz, respectively, while the corresponding values for the external walls were found to be 45 dB to 70 dB. The semi-shielded chamber realized in this work is useful for Fat-IBC technology, brain-computer interface, brain-machine interface, body area networks (BANs), and related applications.