On-Body Cavity-Backed Slot Antenna With Pattern and Polarization Diversity for Medical Imaging

Electromagnetic imaging (EMI) technology has witnessed an increasing interest in medical applications due to its ability to provide noninvasive, portable, and low-cost imaging solutions. The antennas needed in EMI should meet specific requirements to enable efficient and accurate detection of targets with any shape and orientation with reasonable spatial resolution and compatibility with the human body. Therefore, a compact, unidirectional on-body antenna with pattern and polarization diversity is presented as a potential candidate for various medical EMI systems. It comprises two elements of ring slots based on substrate integrated waveguide (SIW). Each element is fed using two orthogonal lines to achieve dual polarization with the same phase center. A matching layer with average dielectric properties of the human tissues is developed, fabricated, and integrated with the antenna to enhance power penetration inside the human body. The antenna has a compact size of $22 {\times }41.5 \times 1.5~{\mathrm {mm}}^{3}$ ( $ 0.058 {\times }0.11 \times 0.004 {\lambda }_{o}^{3}$ , where ${\lambda }_{o}$ is the free space wavelength at the low operating frequency) with wide operational bandwidth (BW) from 0.8 to 2.7 GHz with a front-to-back ratio of 18 dB and a safe level of the specific absorption rate (SAR). The antenna system is tested in the presence of head, torso, and knee models. The results confirm its superior performance compared to recent relevant designs and its suitability for various medical EMI applications.