Planar monopole antennas with reflection plane for human body centric communication

Abstract

Wireless Body Area Network (WBAN) is an emerging technology that requires an antenna to be placed on human body for a wide range of applications such as healthcare, entertainment, surveillance, emergency and military. The reflection coefficient magnitude of the antenna in closeness to the human body is degraded and shifted. Essentially, efficiency and gain reduction are the main disadvantages of the antenna performances due to the body effect. In this research, methods of improving efficiency, gain, Specific Absorption Rate (SAR) and stabilizing reflection coefficient magnitude have been proposed. In this work, the design, simulation and fabrication of two monopole antennas with P-shaped and circular-shaped are presented. The proposed P-shaped monopole antenna is designed to operate from 3.1 to 5.1 GHz while the proposed circular-shaped monopole antenna operates at 3.1-5.1 GHz and 6.5-8 GHz. The simulation of the proposed antennas in free space and close proximity of body surface has been carried out using Computer Simulation Technology (CST) Microwave Studio. It has been found that when the P-shaped and circular elements are introduced to the ground plane of the antennas, the reflection coefficient magnitudes with the presence of body for both antennas remain the same as in free space. Moreover, the efficiency and gain of the antennas have been improved by attaching the glass substrate to the ground plane. P-shaped antenna with the glass substrate has demonstrated about 34.6%, 35% and 39.2% improvement of the antenna efficiency at 3.3, 4.45 and 5 GHz, respectively, when placed directly on the human head. For the human chest placement, the antenna demonstrates 30.7%, 33.4% and 36%, and the gain of 3.4, 2.8 and 4 dBi of antenna efficiency and gain improvement at 3.3, 4.45 and 5 GHz, respectively. Similarly, for circular-shaped monopole antenna the improvement of the antenna efficiency obtained for human head are 39.8% and 37.23% at 3.3 and 7.5 GHz, respectively, and for the chest are 36.5% and 32.8% at 3.3 and 7.5 GHz, accordingly. The antenna demonstrates 2.9 and 2.54 dBi improvement of the gain at 3.3 and 7.5 GHz, respectively. These improvements are compared with the antenna without the glass substrate. This study concludes that the glass substrate has improved the gain, efficiency and SAR when placed near human body compared to other antennas and the S11 remains stable when some additional elements are introduced to the ground plane. It was observed that there is good agreement between the simulation and measurement results, thereby showing that the antennas have potential to be deployed for WBAN application.