Design and Evaluation of a Button Sensor Antenna for On-Body Monitoring Activity in Healthcare Applications

A button sensor antenna for on-body monitoring in wireless body area network (WBAN) systems is presented. Due to the close coupling between the sensor antenna and the human body, it is highly challenging to design sensor antenna devices. In this paper, a mechanically robust system is proposed that integrates a dual-band button antenna with a wireless sensor module designed on a printed circuit board (PCB). The system features a small footprint and has good radiation characteristics and efficiency. This was fabricated, and the measured and simulated results are in good agreement. The design offers a wide range of omnidirectional radiation patterns in free space, with a reflection coefficient (S11) of −29.30 (−30.97) dB, a maximum gain of 1.75 (5.65) dBi, and radiation efficiency of 71.91 (92.51)% in the lower and upper bands, respectively. S11 reaches −23.07 (−27.07) dB and −30.76 (−31.12) dB, respectively, with a gain of 2.09 (6.70) dBi and 2.16 (5.67) dBi, and radiation efficiency of 65.12 (81.63)% and 75.00 (85.00)%, when located on the body for the lower and upper bands, respectively. The performance is minimally affected by bending, movement, and fabrication tolerances. The specific absorption rate (SAR) values are below the regulatory limitations for the spatial average over 1 g (1.6 W/Kg) and 10 g of tissues (2.0 W/Kg). For both indoor and outdoor conditions, experimental results of the range tests confirm the coverage of up to 40 m

Recent advances of wearable antennas in materials, fabrication methods, designs, and their applications: state-of-the-art

The demand for wearable technologies has grown tremendously in recent years. Wearable antennas are used for various applications, in many cases within the context of wireless body area networks (WBAN). In WBAN, the presence of the human body poses a significant challenge to the wearable antennas. Specifically, such requirements are required to be considered on a priority basis in the wearable antennas, such as structural deformation, precision, and accuracy in fabrication methods and their size. Various researchers are active in this field and, accordingly, some significant progress has been achieved recently. This article attempts to critically review the wearable antennas especially in light of new materials and fabrication methods, and novel designs, such as miniaturized button antennas and miniaturized single and multi-band antennas, and their unique smart applications in WBAN. Finally, the conclusion has been drawn with respect to some future directions

Design of new wearable antennas and textile-based transmission lines

Flexible wearable antennas and their components are a fast growing research topic in modern communication systems. They are developed for various wearable applica tions, such as health monitoring, fitness tracking, rescuing, and telecommunications. Wearable antennas need to be compact, lightweight, flexible, and robust. In this thesis, two dual-band wearable antennas were developed, each with a differ ent design approach. The first antenna is a dual-band flexible folded shorted patch (FSP) antenna which operates at 400 MHz and 2.4 GHz. It uses polydimethylsilox ane (PDMS), which is low cost, flexible and robust, and is used as a substrate for wearable the FSP antenna. In addition, the FSP antenna also exploits the TM010 and TM001 modes. A comparative study was carried out to analyze the far-field radiation and directivity at the TM010 and TM001 modes between the FSP antenna and a conventional patch antenna using cavity model analysis. The proposed FSP antenna is suitable for military search and rescue operations and emergency services. The second antenna is a dual-band flexible circular polarized (CP) patch antenna operational at 1.575 GHz and 2.45 GHz. Kevlar was used as a substrate for the proposed antenna. The patch consists of truncated corners and four diagonal slits. An artificial magnetic conductor (AMC) plane was integrated within the design in order to reduce the backward scattered radiation towards the human body and also to improve the realized gain of the antenna. The AMC unit cell design consists of square slits, a square ring and was integrated as a 3 × 3 array of square patch AMC unit cells. The proposed antenna developed is suitable for WBAN and WLAN applications. A circular polarized (CP) patch antenna with a PDMS substrate was also designed and fabricated to test the durability and resiliency of PDMS as a polymer-based material suitable for use in wearable antennas. Robustness tests such as bent, wet, and temperature tests were performed and reported. Two prototypes of flexible wearable coaxial transmission lines were also designed and fabricated. Polyester (PES) and polytetrafluoroethylene (PTFE) textile materials were used to design prototypes of these cables. Shielding effectiveness and DC losses were measured and compared for the fabricated cables. The cables were also tested for bending, twisting and for suitability in environmental conditions. The highly flexible nature of these cables makes them suitable to use with wearable antennas for various applications. For example, the proposed cables can be used with previously detailed FPS antenna for military search and rescue operations. It should be mentioned that this thesis was done in collaboration with Leonardo, UK and J&D Wilkie, UK