Dual-turn electrically coupled loop antenna for gastrointestinal capsules

Abstract

A dual turn electrically coupled loop antenna is proposed to operate inside gastrointestinal capsules. The proposed structure is simple with a degree of freedom in design and compact size. In addition, it has low specific absorption rate (SAR) levels. Four different models have been designed to operate at industrial, scientific, medical (ISM) bands (433 MHz and 915 MHz). The first three antenna models with different sizes operate at the 433 MHz ISM band while the fourth antenna model operates at the 915 MHz ISM band. The primitive designs are performed by immersing the biocompatible-encapsulated prototypes inside the center of a cubic box of muscle phantom with an edge length of 100 mm. To mimic the realistic situation, the final designs were simulated inside a human torso model. As an experimental verification, a prototype has been fabricated and tested inside minced beef. The footprint size excluding the space in the core is 200 mm3. The peak SAR levels, averaged on 1 g, are 78.4, 51.8 and 81.67 W/kg for the three proposed antennas, respectively. The low SAR levels permit increasing the fed power to compensate medium losses in addition to obtain better imaging. The peak realized gains in muscle lie in the range of the other counterparts (− 19 dBi).