Simultaneous Wireless Powering and Biotelemetry for Biomedical Implants Using 3-D Printable Water-Based Self-Diplexing Antennas

This paper presents water-based single-input single-output (SISO) and multiple-input multiple-output (MIMO) self-diplexing antennas designed for implantable devices. The SISO water-based self-diplexing (WBSD) antenna is designed with two elements of different heights: the element with a height of 7 mm resonates at 1.45 GHz for wireless power transfer (WPT), and the other with a height of 4.2 mm resonates at 2.45 GHz for bio-telemetry. To convert the SISO into a MIMO, the circular radiators are repositioned towards the boundary and mirrored to the opposite boundary of the antenna. The operating frequencies of both versions can be customized by adjusting their heights and radii. These SISO and MIMO self-diplexers are considered more safer for users as they use water and metal without any slots. To create an efficient system capable of both biotelemetry and battery recharging, the WBSD antenna prototypes are connected to a full-wave rectifier inside a capsule device, and different tests are performed. The efficiency of the wireless power transfer (WPT) is improved by about 30% using the spatial power combining (SPC) techniques. Both the SISO and MIMO self-diplexers can be produced using a 3-D printer and copper tapes, resulting in lower production costs.