Textile antenna with simultaneous frequency and polarization reconfiguration for WBAN

This paper proposes the design of a reconfigurable circularly polarized textile antenna. The circular polarization feature in the proposed antenna is generated by the edge-truncation of a rectangular patch and the incorporation of a slotted ground plane, whilst the frequency re-configurability feature is realized by slot size modification via the use of three embedded RF PIN diode switches. Consequently, the antenna operation can be switched between six frequencies (1.57 GHz, 1.67 GHz, 1.68 GHz, 2.43 GHz, 2.50 GHz and 2.55 GHz) depending on the seven switch configurations. The proposed antenna is validated experimentally to be operable within the WBAN, WLAN and GPS range in a compact and wearable format, with gains of up to 4.8 dBi

Wearable antennas: a review of materials, structures, and innovative features for autonomous communication and sensing

Wearable antennas have gained much attention in recent years due to their attractive features and possibilities in enabling lightweight, flexible, low cost, and portable wireless communication and sensing. Such antennas need to be conformal when used on different parts of the human body, thus need to be implemented using flexible materials and designed in a low profile structure. Ultimately, these antennas need to be capable of operating with minimum degradation in proximity to the human body. Such requirements render the design of wearable antennas challenging, especially when considering aspects such as their size compactness, effects of structural deformation and coupling to the body, and fabrication complexity and accuracy. Despite slight variations in severity according to applications, most of these issues exist in the context of body-worn implementation. This review aims to present different challenges and issues in designing wearable antennas, their material selection, and fabrication techniques. More importantly, recent innovative methods in back radiations reduction techniques, circular polarization (CP) generation methods, dual polarization techniques, and providing additional robustness against environmental effects are first presented. This is followed by a discussion of innovative features and their respective methods in alleviating these issues recently proposed by the scientific community researching in this field

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

Recent developments and state of the art in flexible and conformal reconfigurable antennas

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Reconfigurable antennas have gained tremendous interest owing to their multifunctional capabilities while adhering to minimalistic space requirements in ever-shrinking electronics platforms and devices. A stark increase in demand for flexible and conformal antennas in modern and emerging unobtrusive and space-limited electronic systems has led to the development of the flexible and conformal reconfigurable antennas era. Flexible and conformal antennas rely on non-conventional materials and realization approaches, and thus, despite the mature knowledge available for rigid reconfigurable antennas, conventional reconfigurable techniques are not translated to a flexible domain in a straight forward manner. There are notable challenges associated with integration of reconfiguration elements such as switches, mechanical stability of the overall reconfigurable antenna, and the electronic robustness of the resulting devices when exposed to folding of sustained bending operations. This paper reviews various approaches demonstrated thus far, to realize flexible reconfigurable antennas, categorizing them on the basis of reconfiguration attributes, i.e., frequency, pattern, polarization, or a combination of these characteristics. The challenges associated with development and characterization of flexible and conformal reconfigurable antennas, the strengths and limitations of available methods are reviewed considering the progress in recent years, and open challenges for the future research are identified

VLSI Implementation of an Efficient Lossless EEG Compression Design for Wireless Body Area Network

Data transmission of electroencephalography (EEG) signals over Wireless Body Area Network (WBAN) is currently a widely used system that comes together with challenges in terms of efficiency and effectivity. In this study, an effective Very-Large-Scale Integration (VLSI) circuit design of lossless EEG compression circuit is proposed to increase both efficiency and effectivity of EEG signal transmission over WBAN. The proposed design was realized based on a novel lossless compression algorithm which consists of an adaptive fuzzy predictor, a voting-based scheme and a tri-stage entropy encoder. The tri-stage entropy encoder is composed of a two-stage Huffman and Golomb-Rice encoders with static coding table using basic comparator and multiplexer components. A pipelining technique was incorporated to enhance the performance of the proposed design. The proposed design was fabricated using a 0.18 μm CMOS technology containing 8405 gates with 2.58 mW simulated power consumption under an operating condition of 100 MHz clock speed. The CHB-MIT Scalp EEG Database was used to test the performance of the proposed technique in terms of compression rate which yielded an average value of 2.35 for 23 channels. Compared with previously proposed hardware-oriented lossless EEG compression designs, this work provided a 14.6% increase in compression rate with a 37.3% reduction in hardware cost while maintaining a low system complexity

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

Reconfigurable Antennas

In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance