Dual-band wearable textile antenna on an EBG substrate

Performance of a dual-band coplanar patch antenna integrated with an electromagnetic band gap substrate is described. The antenna structure is made from common clothing fabrics and operates at the 2.45 and 5 GHz wireless bands. The design of the coplanar antenna, band gap substrate, and their integration is presented. The band gap array consists of just 3 x 3 elements but reduces radiation into the body by over 10 dB and improves the antenna gain by 3 dB. The performance of the antenna under bending conditions and when placed on the human body are presented

Textile Diamond Dipole and Artificial Magnetic Conductor Performance under Bending, Wetness and Specific Absorption Rate Measurements

Textile diamond dipole and Artificial Magnetic Conductor (AMC) have been proposed and tested under wearable and body centric measurements. The proposed antenna and AMC sheet are entirely made of textiles for both the substrate and conducting parts, thus making it suitable for wearable communications. Directive radiation patterns with high gain are obtained with the proposed AMC sheet, hence minimizing the radiation towards the human body. In this study, wearable and body centric measurements are investigated which include bending, wetness and Specific Absorption Rate (SAR). Bending is found not to give significant effect to the antenna and AMC performance, as opposed to wetness that yields severe performance distortion. However, the original performance is retrieved once the antenna and AMC dried. Moreover, notable SAR reduction is achieved with the introduction of the AMC sheet, which is appropriate to reduce the radiation that penetrates into human flesh

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

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

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

Electromagnetic Band Gap Structure Integrated Wearable Monopole Antenna For Spacesuit

Research and development of body-worn communication systems and electronics have become very prominent in recent years. Some applications include intelligent garments equipped with wireless communication devices for sports, astronauts’ spacesuits [1], and fire fighters’ uniforms [2]. These systems are unthinkable without different kinds of body worn textile or flexible antennas. In this thesis, we will discuss the design and fabrication of a compact wearable textile antenna within the Industrial, Scientific and Medical (ISM) band operating frequency, proposed for incorporation into a flight jacket of the astronaut inside the habitat. The antenna is integrated with artificial material known as Electromagnetic Band Gap (EBG) structures for performance enhancement. The purpose of the system is to constantly monitor vital signals of the astronauts. In this thesis the design, simulation, prototype fabrication and antenna testing under different environmental condition, in a word the entire design cycle of wearable Co-Planar Waveguide (CPW) fed monopole antenna is discussed. As human body tissues are lossy in nature, the radiation efficiency of the antenna will be affected due to the absorption of the radiated energy. Therefore, alteration in the radiation characteristics of the wearable antenna like resonant frequency, realized gain and impedance bandwidth will take place. For overcoming these obstacles, addition of EBG layers are recommended to isolate the antenna from near body environments. The proposed wearable antenna was tested under real operating conditions such as pressure and stretching conditions

Design, Analysis and Applications of Wearable Antennas: A Review

Wearable antennas are the vital components for Body Centric Communication (BCC). These antennas have recently gained the attention of researchers and have received a great deal of popularity due to their attractive characteristics and opportunities. They are fundamental in the Wireless Body Area Networks (WBANs) for health care, military, sports, and identification purposes. Compared to traditional antennas, these antennas work in close proximity to the human body, so their performance in terms of return loss, gain, directivity, bandwidth, radiation pattern, efficiency, and Specific Absorption Rate (SAR) is influenced by the coupling and absorption of the human body tissues. Additionally, in the design of these antennas, size, power consumption, and speed can also play a paramount role. In most cases, these antennas are integrated into the clothes, or in some cases, they may be fixed over the skin of the users. When these characteristics are considered, the design of wearable antennas becomes challenging, particularly when textile materials are examined, high conductivity materials are used during the manufacturing process, and various deformation scenarios have an impact on the design’s performance. To enhance the overall performance of the wearable antennas and to reduce the backward radiation towards the human body, metamaterial surfaces are introduced that provide a high degree of isolation from the human body and significantly reduce the SAR. This paper discusses the state-of-the-art wearable/textile/flexible antennas integrated with metamaterial structures composed of wearable/flexible substrate materials, with a focus on single and dual band antenna designs. The paper also reviews the critical design issues, various fabrication techniques, and other factors that need to be considered in the design of wearable/textile/flexible antennas. All the designs presented in this work are of the recent developments in wearable technology

Slot Antennas - A Comprehensive Survey

Wireless Communication has found a rapid growth over the past decades starting from handheld devices to spacecraft applications. The efficient operation of all such wireless devices depends on the design and proper working of the transmitting and receiving antennas. Microstrip antennas are most commonly preferred for major wireless applications, because of their miniaturized structure, ease of fabrication, low power consumption, flexibility with printed circuit board, low profile, light weight, effective return loss and better radiation properties. This paper provides a comprehensive survey on microstrip antennas whose performance is improved to meet the increasing demand, by introducing slots of different shapes and sizes. These slots of various kinds helps in obtaining wider bandwidth over the C and Ultrawideban

Flexible Transmission Lines and Asymmetrically Counter-Poised Monopoles

In the pursuit of miniaturised antennas and flexible transmission lines, several techniques have been explored in the open literature to address physical aspects of size, weight, flexibility and electrical reconfigurability, all whilst sustaining a reasonable degree of electrical operation. In the first part of this thesis, these themes are further explored with transmission lines, through the experimentation of transmission lines that use standard, readily available materials of a conformal nature, that would appreciably suit our context of operation. Two distinct types of transmission lines are designed, simulated, investigated and reported on. In the second half of this thesis, we explore asymmetrical antenna design in relation to antenna miniaturisation, aiming at creating a design method for this type of antennas. The first transmission line examined in the first part of the thesis, is what we now refer to as a Wire-Over-Ground-Plane transmission line. Structurally, this is standard gauge wire, placed over a polyimide sheet beneath which exists ground plane. A model of this transmission line is created and thereafter numerically simulated. A rough prototype of this design was created to validate operation. Thereafter, proposed is the design with realistic simulations of a branch-line coupler and modified Marchand balun, using this technology. The second transmission line created, is a stripline transmission line constructed primarily from fleece and a conductive textile. Once more, this structure is numerically simulated to validate operation prior to construction. Thereafter a number of samples are created to explore the physical robustness of the connection, through the application of mechanical stress and strain of varied transmission line constructions. In the second part of the thesis three antennas were created taking an asymmetrical approach to antenna realisation. The first Counter-Poised monopole antenna is experimentally realised by replacing one of the dipole arms with a coil of equivalent inductance. Decent performance here led to a second antenna design that builds on the first asymmetrical design, implementing a planar integrated balun into the feed-structure and developing a planar counter-poise fabricated on a circuit board. The third antenna design, builds further on the second design by adding a frequency reconfigurability feature through the addition of active circuit elements to the counter-poise. As we worked from developing the experimental antenna to realising the frequency reconfigurable variant, we have sought to understand the principle of operation and establish a design method which has allowed for the development of an advanced reconfigurable variant. The counter-poise is the fulcrum of all three asymmetrical antennas designed here, so a thorough grasp on its design and operation is required to ensure adequate antenna operation. In summation, this thesis develops ideas and realisations of flexible transmission lines using standard off-the-shelf components as well as conductive textiles and clothing. Further, asymmetrical antenna design techniques are explored leading to antenna miniaturisation. Thereafter, design methods are developed to aid in planar fixed-frequency implementation, whereupon a more advanced frequency reconfigurable variant is created.Thesis (MPhil) -- University of Adelaide, School of Electrical and Electronic Engineering, 202

High Gain Pattern Reconfigurable Antenna Arrays for Portable and Body-Centric Wireless Applications

Wireless devices such as smartphones, tablet computers, smartwatches etc. have become ubiquitous. With that, the demand for high speed data has increased tremendously. Designing antennas for such applications is challenging because of limited availability of space, shadowing or blockage from the human body, and signal loss from multipath fading. Conventional broad, fixed beam low gain antennas result in poor reception, faster battery drainage, and low data rate. Compressed footprint high gain pattern reconfigurable antenna arrays can solve these problems which is the focus of this dissertation. Two innovative high gain pattern reconfiguration techniques, the switched beam parasitic array and the varactor controlled series-fed phased array are studied and developed. First, by taking advantage of the controlled coupling between closely spaced driven and parasitic dipoles, a compressed footprint beam steering array is developed for handheld devices. By optimizing the interelement spacing and the ON/OFF states of the RF switches located at the input of the parasitic dipoles, beam steering in the azimuth plane is achieved. Furthermore, a collinear arrangement of subarrays allows narrow elevation plane beamwidth and gain of up to 11 dBi. By contrast, typical handheld device antennas have about 3 dBi gain and little or no steering ability. System level analysis shows about 59% improvement in signal-to-interference-plusnoise ratio level over traditional omnidirectional antennas. Second, a high gain switched beam parasitic array is proposed based on fabric materials which can be integrated within the clothing or uniforms of first responders. Material sensitivity analyses considering various conductive and nonconductive fabrics are performed. Studies of the array near a multilayered human body phantom reveal that a minimum distance from the body is required for the array to allow beam steering and high gain. For example, with 10 mm spacing from the body −300 to 300 steering is achieved with 10 dBi peak gain which are excellent for high throughput communication. Third, a novel concept to design ultrathin directional broadband antennas using a nonuniform aperiodic (NUA) metasurface is introduced. By employing a decreasing taper for both the metasurface patch and their interelement spacing, broad impedance and pattern bandwidths are attained. Experimental results show that, with a total thickness of 0.04 free-space wavelength at the lowest frequency of operation, an octave bandwidth can be obtained, which is significantly larger compared with existing designs on uniform mushroom electromagnetic band-gap structures. Based on the NUA metasurface, a thin switched beam (00, 250, and 3350) parasitic antenna array is presented which with a thickness of 0.04 wavelength can attain high gain (8.4 dBi) and very high front-to-back ratio. Finally, to overcome the challenges of wide and overlapping beams with parasitic arrays, and the space constraint and circuit complexity required by phased arrays, a new varactor controlled series-fed phased array is proposed for wearable applications. At the center of the design is a varactor controlled phase shifter, where varactor capacitance is changed by applying different bias voltages which alters the progressive phase between series-fed antenna input currents and allows array pattern to be reconfigured. Low return loss, high gain, and beam steering with nulls between two consecutive beams are achieved. It is observed that the choice of substrate and varactors are critical to minimize loss. While the works presented here reflect the 5 GHz frequency band the design and ideas are likely scalable and adaptable for next generation mm-wave systems operating at 28, 38, and 60 GHz