Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

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.

/pdf/wearable-antennas-a-review-of-materials-structures-and-5bzxx4cp70.pdf

Wearable Antennas: A Review of Materials, Structures, and Innovative Features for Autonomous Communication and Sensing

A new type of wearable button antenna for wireless local area network (WLAN) applications is proposed. The antenna is composed of a button with a diameter of circa 16 mm incorporating a patch on top of a dielectric disc. The button is located on top of a textile substrate and a conductive textile ground that are to be incorporated in clothing. The main characteristic feature of this antenna is that it shows two different types of radiation patterns, a monopole type pattern in the 2.4 GHz band for on-body communications and a broadside type pattern in the 5 GHz band for off-body communications. A very high efficiency of about 90% is obtained, which is much higher than similar full textile solutions in the literature. A prototype has been fabricated and measured. The effect of several real-life situations such as a tilted button and bending of the textile ground have been studied. Measurements agree very well with simulations.

Wearable Button Antenna for Dual-Band WLAN Applications With Combined on and off-Body Radiation Patterns

In this letter, a wearable all-textile metasurface antenna (MSA) for 5 GHz wireless body area network (WBAN) applications is proposed. All the components of the proposed MSA are made of the comfort textile materials. A metasurface with high permittivity values is placed right above a wide-bandwidth planar inverted-F antenna to realize size miniaturization and gain enhancement. The proposed MSA has a profile of 4 mm (0.07 λ 0) and occupies an area of 42 mm × 28 mm (0.77 λ 0 × 0.51 λ 0). Moreover, this antenna realizes a measured peak gain of 6.70 dBi, an average efficiency of 77%, and an operating band from 4.96 to 5.90 GHz that covers the 5 GHz WBAN band. In addition, the on-body studies show that the MSA is suitable for wearable applications.

A Wearable PIFA With an All-Textile Metasurface for 5 GHz WBAN Applications

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems.

/pdf/wideband-and-uwb-antennas-for-wireless-applications-a-1yabyj5rhz.pdf

Wideband and UWB Antennas for Wireless Applications: A Comprehensive Review

A compact substrate integrated waveguide (SIW) based wearable tri-band leather antenna, designed for optimal on-body performance in the 2.4 GHz (ISM), 3.51 GHz (WiMAX) and 4.69 GHz (Military application) bands is proposed. By using brass eyelets and a combination of conducting and non-conductive leather materials, a substrate integrated waveguide cavity with a ground plane is realised. The antenna is very compact, flexible and directs radiation away from the wearer
 .
 Additional miniaturisation is achieved by introducing slits. The free space performance in the bands is found satisfactory with measured impedance bandwidths of 11, 7 and 5%, maximal measured free-space gains of 1.1, 0.9 and 2.1 dBi, and efficiencies of 71.3%, 68.2% and 76.5% achieved for the proposed antenna.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/el.2015.2559

Wearable tri-band SIW based antenna on leather substrate

A compact U-shaped defective ground structure (DGS) and an inverted U-shaped resonator are introduced in order to reduce the mutual coupling (MC) between two slotted microstrip antennas at two difierent resonance frequencies. The proposed DGS and resonator have the same electrical length and both are placed in between two patch antennas, as a technique to suppress the occurrence of MC at two difierent frequency bands. The DGS and the resonator ofier stop bands at 2.45GHz and 4.5GHz respectively. Simulated results show a reduction in MC of 20dB at 2.45GHz band and 1dB at 4.5GHz band. We have developed experimental models that have proved this concept of MC reduction. Finally, the in∞uence of other parameters of the proposed antenna at the presence of the combination of DGS and resonator in the array system has been studied. Prototype antennas for difierent combinations of DGS and resonator and two-element array integrated with DGS and resonator have been fabricated, measured and the idea has been verifled. A good agreement is observed between measured and the simulated results.

/pdf/mutual-coupling-reduction-of-a-dual-frequency-microstrip-3i0frb8spu.pdf

Mutual Coupling Reduction of a Dual-Frequency Microstrip Antenna Array by Using U-Shaped DGS and Inverted U-Shaped Microstrip Resonator

A compact miniaturized wearable antenna with the appearance of a button on clothing for Wi-Fi and Wi-Max applications as well as used for body centric communication is presented. The radiating elements of the antenna are made of copper tape, while the substrate is given a property of transparent acrylic fiber sheet material and fed by a coaxial line through the ground plane. The proposed antenna is simulated by Ansoft HFSS finite element method based simulation software and has been optimized to operate within the Wi-Fi and Wi-Max frequency bands with center frequency of 5.5 GHz (5250–5850 MHz). The measured peak gain of this antenna is 2.92 dBi. There is a good matching between the simulated and the measured result. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:45–49, 2015

A miniaturized wearable button antenna for Wi‐Fi and Wi‐Max application using transparent acrylic sheet as substrate

In this article a compact miniaturized wearable antenna with the appearance of a button on clothing for WLAN applications is presented. The radiating elements of the antenna are made of copper sheet, whilst a transparent acrylic fiber sheet material is used as substrate and fed by a coaxial line through the ground plane. The proposed antenna is simulated by Ansoft HFSS FEM based EM simulator and has been optimized to operate within the WLAN frequency bands with centre frequency of 5.25 GHz (5250–5850 MHz). A split ring-shaped slot based frequency selective surface (FSS) is designed to enhance the gain of the proposed antenna. The peak gain of the antenna is enhanced from 2.1dBi to 5.1dBi with the superstrate along with a bandwidth enhancement of 290MHz. The antenna gets miniaturized around 34% by the slit.

A wearable button antenna with FSS superstrate for WLAN health care applications

In this letter, a low profile circularly polarized wearable antenna with the appearance of a button on clothing for Wi-Fi and WLAN applications is presented. The radiating elements of the antenna are made of copper sheet while a transparent acrylic fiber sheet material is used as substrate and fed by a coaxial line through the ground plane. The proposed antenna is simulated by Ansoft high frequency structure synthesis finite element method-based (HFSS FEM)-based EM simulator and has been optimized to operate within the Wi-Fi and WLAN frequency bands (5250-5850 MHz) with center frequency of 5.25 GHz. A split ring- shaped slot-based frequency selective surface (FSS) is designed to enhance the gain of the proposed antenna. The peak gain of the antenna is found to increase from the conventional antenna gain of 2.1 to 5.1 dBi with the superstrate along with a bandwidth enhancement of 290 MHz. The composite FSS antenna is fabricated and the maximum measured gain of 5.1 dBi matches well with theoretical value. The antenna gets miniaturized around 34% by the slits with its circular polarization charac-

Bappaditya Mandal

Papers

Wearable tri-band SIW based antenna on leather substrate

Mutual Coupling Reduction of a Dual-Frequency Microstrip Antenna Array by Using U-Shaped DGS and Inverted U-Shaped Microstrip Resonator

A miniaturized wearable button antenna for Wi‐Fi and Wi‐Max application using transparent acrylic sheet as substrate

A wearable button antenna with FSS superstrate for WLAN health care applications

Acrylic substrate based low profile wearable button antenna with FSS layer for WLAN and Wi-Fi applications