A multiband magnetic type wearable antenna for wireless patient monitoring applications

Wearable technology application has become one of the important part in the development of Body Centric Wireless Communications Systems (BWCS). Wearable antenna is an important device aimed at those applications in particular for medical purposes, safety purposes, and so on. However, most of the antenna design is still focused on the electrical type antenna, while the magnetic type antenna is rarely explored in many studies so far. In this paper, a multiband wearable antenna with magnetic characteristics is proposed for biomedical applications, especially for wireless patient monitoring, which works on multiband frequency of 0.924 GHz (RFID), 2.45 GHz (WLAN) and 5.8 GHz (WLAN). The proposed antenna is constructed of a textile substrate and a copper patch on the substrate. Based on the link budget that we have calculated, the antenna is specified by the magnitude of reflection coefficient (in terms of S₁₁ parameter) less than -10 dB (VSWR ≤ 2) and the required gain according to each technology at each operating band. In addition, in order to investigate the effect of the proximity human body on the performance of the antenna, a phantom model is used, consisting of three types of emulated tissues: skin, fat, and muscle. To numerically simulate the antenna design, CST Microwave Studio is used to get robust antenna performance in two main conditions, i.e., without and with the phantom model. We have also study about the magnetic characteristics of the antenna by characterizing the electric and magnetic field distribution in the near field environment, which the dominant magnetic distribution is obtained. To ensure the antenna performance when it works in the vicinity of human body, the antenna is simulated on the phantom model. Since the antenna is magnetic type, it generally does not change the antenna basic parameters significantly, especially in terms of resonant frequency, bandwidth, pattern and gain. In addition, to limit harmful effect to the human body, specific absorption rate (SAR) characteristic is investigated at a distance by 0 to 20mm from the phantom to the body surface.