Optimal Flexible Antenna Designs for Future WBAN

Abstract

Health and long term care is growing exponentially in wearable biomedical systems. Wearable and flexible diagnostic systems can contribute towards the timely care of patients suffering with chronic health conditions, particularly chronic neurological disorders and cardiovascular diseases. Thousands of lives can be save by using diagnostics and therapeutic techniques. Existing ambulatory system is not able to perform continuous remote monitoring of patients. From the literature review, it is stated that flexible wearable electronic systems have gained intense attention in the last two decades. Wearable antennas have an enormous potential in future healthcare and children applications. The performance such as durability, flexibility, compactness and configurability of flexible antenna is much better than other devices. Due to these reasons the performance process of flexible wearable antenna should be evaluated. The power consumption demand is really dependent on the peculiar application of wearable antennas. However, WBAN devices are mostly battery powered and the battery life time is required to be up to several years. This dissertation shows the designs of flexible and wearable antenna used for biomedical applications in the near vicinity of the human torso. Primarily, a planar flexible antenna is designed on a flannel substrate with the permittivity of 1.45, 2mm thickness and loss tangent of 0.044. The antenna consists of shield conductive textile with a four-sided slot and a compact ground plane to improve the impedance matching characteristics which provides wider bandwidth. The proposed antenna is designed with a flimsy and flexible textile substrate with a measured reflection coefficient below -10dB. Antenna parameters such as radiation pattern, bandwidth, gain and radiation pattern are evaluated by using measurements and simulations. The projected design has low power consumptions due to the accomplishment of gain results that was less than 5dB in the frequency between 3GHz and 15GHz. Additionally, this work explores the possibilities of using natural rubber in the conception of a simple microstrip patch antenna. The antenna is designed to work in the UWB spectrum, and the properties of substrate such as thickness, metal width and permittivity are measured. From the results it is concluded that the return loss of the antenna is significantly amended due to the decrease in the substrate thickness and permittivity. In disparity, decreasing the metal thickness will increase the return loss. It is observed, that thicker substrate will yield higher directivity, and lower value of relative permittivity will result in lower directivity. ix Finally, the proposed flexible antennas are validated to meet the requirements for wearable devices, such as being flexible, compact and mechanically robust. Therefore, the influence of bending and wet conditions is also investigated. The simulated and measured results show that the proposed models give satisfactory results under bending and wet environments.