On the Effects of Balun on Small Antennas Performance for Animal Health- Monitoring and Tracking

This paper presents the performance evaluation of a sleeve Balun integration in the design of a flexible loop antenna for wildlife health monitoring and tracking applications. To verify the design concept, an experimental antenna is designed, fabricated, and measured in free-space and muscle mimicking phantom. Moreover, investigations are carried out for wearable and implanted antennas in planar and conformal arrangements. In free-space, the antenna is operating within the industrial, scientific, and medical ISM 5.8 GHz band. Balun integration in the antenna design efficiently chokes the currents excited on the outer surface of the feeding cable and provides a good impedance match between antenna and feed line, as demonstrated by simulation and measurement results. On the other hand, in phantom, the antenna has a wide bandwidth characteristic that covers the most used frequency bands for in-body devices. Balun integration, in this case, showed a negligible effect on antenna’s matching properties for two studied implantation depths; 2.5 cm and 5 cm.  The proposed study offers a promising guideline in the design and realization of wearable and implanted antennas.