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.

This paper presents a novel approach to design compact wearable antennas based on metasurfaces. The behavior of compact metasurfaces is modeled with a composite right-left handed transmission line (CRLH TL). By controlling the dispersion curve, the resonant modes of the compact metasurface can be tuned efficiently. A printed coplanar waveguide (CPW) monopole antenna is used as the feed structure to excite the compact metasurface, which will result in a low profile antenna with low backward radiation. Following this approach, two compact antennas are designed for wearable applications. The first antenna is designed to operate at its first negative mode (-1 mode), which can realize miniaturization, but maintain the broadside radiation as for a normal microstrip antenna. The proposed prototype resonates around 2.65 GHz, with a matching bandwidth of 300 MHz. The total dimensions of the antenna are 39.4x33.4 mm2 (0.1 λ02), and its maximum gain is 2.99 dBi. The second antenna targets dual-band operation at 2.45 GHz and 3.65 GHz. A pair of symmetric modes (±1 modes) are used to generate similar radiation patterns in these two bands. The size of the antenna is 55.79x52.25 mm2 (0.2 λ02), and the maximum gains are 4.25 dBi and 7.35 dBi in the two bands, respectively. Furthermore, the performance of the antennas is analyzed on the human body. The results show that the proposed antennas are promising candidates for Wireless Body Area Networks (WBAN).

Ultrawideband (UWB) technology can provide short-range, high bandwidth communications at a very low energy consumption level, which is quite attractive for wireless body area networks (WBAN). In such a system, the presence of the human body brings huge challenges for both the design of the wearable antenna and the propagation model. First of all, the coupling between the wearable antenna and the human body should be considered even in the initial steps of the design, in order to be able to deal with both the possibly deteriorating performance of the antenna as a result of the body and the exposure risk for the body. Second, the propagation channel in WBAN is influenced by the continuous movement of the human body, due to the time-varying scattering of the electromagnetic waves. Lots of researchers have been active in this area and some significant progress has been achieved recently. This paper retrospects the latest results in the field of wearable ultrawideband antennas, propagation channels, and their respective application in WBAN systems.

Wireless Body Area Network (WBAN) has attracted more and more attention in many sectors of society. As a critical component in these systems, wearable antennas suffer from several serious challenges, e.g., electromagnetic coupling between the human body and the antennas, different physical deformations, and widely varying operating environments, and thus, advanced design methods and techniques are urgently needed to alleviate these limitations. Recent developments have focused on the application of metamaterials in wearable antennas, which is a prospective area and has unique advantages. This article will review the key progress in metamaterial-based antennas for WBAN applications, including wearable antennas involved with composite right/left-handed transmission lines (CRLH TLs), wearable antennas based on metasurfaces, and reconfigurable wearable antennas based on tunable metamaterials. These structures have resulted in improved performance of wearable antennas with minimal effects on the human body, which consequently will result in more reliable wearable communication. In addition, various design methodologies of meta-wearable antennas are summarized, and the applications of wearable antennas by these methods are discussed.

This paper presents a compact textile antenna design based on a metasurface for wearable applications. It operates in the 2.45 GHz and 5.5 GHz industrial, scientific, and medical bands. A two-dimensional equivalent circuit model is proposed to provide insight into the working principle of the metasurface. The tuning of the radiator's resonant frequencies can be easily performed by adjusting the dispersion curve of the metasurface unit cell. The metasurface in this work consists of a 4 × 4 array of unit cells fed by a printed coplanar waveguide structure with a slot in its reverse side to maintain its low profile structure. The main innovations of this work are: (i) the −2 ^nd mode is employed to significantly miniaturize the antenna dimensions; (ii) the simultaneous excitation of the +1 ^st mode to enable dual-band operation; (iii) an integrated back reflector to reduce back radiation and lower SAR; and (iv) the use of full textile materials to guarantee user comfort, ease of fabrication and low cost. The proposed antenna's footprint is 44.1 × 44.1 mm ² (0.12 λ ² at 2.45 GHz), with an impedance bandwidth of 10.2% centered at 2.45 GHz and 22.5% at 5.5 GHz. The maximum gain is −0.67 dBi and 7.4 dBi in free space, and 9% of power gain attenuation is generated when used on the body, and is suitable as a miniaturized antenna for wearable applications.