A Study on Body Communication Antennas

Abstract

This thesis presents the antennas for in-body, on-body communication. The antennas in body communication are severely affected by human body which has a high relative permittivity and conductivity. The high relative permittivity and conductivity degrades the antenna bandwidth and efficiency. Therefore, it is a main challenge that enhancing the bandwidth and the efficiency of the antenna maintaining the small size. In order to enhance the performance of the antennas several techniques are proposed in body communication antennas. Firstly, the Q value and the efficiency of the in-body antenna are investigated. Using the proposed equations, the optimum frequency of the in-body antenna will be given. To maximize the antenna dimensions in the endoscopy antenna, the outer wall loop antennas is proposed. The measurement results are given to show the performance of the proposed antenna. Secondly, the several techniques for on-body antenna are proposed. The conventional antennas without the ground plane like dipole and slot antennas are not appropriate for on-body environment because the body has low intrinsic impedance and high conductivity compared to that of the free space. Therefore, antennas with ground plane like patch and cavity-backed slot antennas are proposed for on-body communication. The cavity-backed slot antenna with via-hole above the slot is proposed for bandwidth enhancement of the antenna. As the place of the via-hole introduces the additional resonance, wider bandwidth is achieved. The substrate removal technique for cavity-backed slot antenna is also proposed for the bandwidth and the efficiency enhancement. The removal of the substrate across the slot decreases the Q of the antenna, increasing the bandwidth and efficiency. In addition, the folded-cavity-backed slot antenna is given for size miniaturization of the cavity-backed slot antenna. The folded structure of the proposed antenna increases the effective length of the antenna, decreasing the antenna resonance frequency. Furthermore, the reconfigurable shorted patch antenna is given for wide bandwidth. Lastly, the dual-band and dual-impedance cavity-backed slot antennas are given for the efficient on-body systems