Wearable textile antennas

Finally, communication is realized in a wireless way by means of an integrated wearable textile antenna in combination with a wearable transceiver. Such a kind of wireless communication takes place between the human body and the surrounding environment and is also referred to as body-centric communication. In parallel with textile antennas, this has become a very popular field of research over the last decade [1], with cmcial importance for plenty of applications, ranging from monitoring of vital signs of patients to coordination and monitoring of rescue workers [2], but also in the entertainment sector [3] and in sports [4]. 

Suitable topologies for the realization of wearable textile antennas exhibit a low profile and compact dimensions. Those features are particularly convenient for on-body placement and seamless integration into garments. For this reason, the majority of existing textile antennas are microstrip or patch antennas. 

When dealing with wearable textile antennas, several adverse effects, which influence the performance characteristics, often occur. It is very important for the design engineer to be able to efficiently model these effects in order to predict variations in antenna performance. The main adverse effects that are treated in the present literature on textile antennas are briefly summarized as follows. 

The presence of the human body in close proximity to a wearable textile antenna is the most common cause of its performance degradation, since the radiator is integrated into garments and, hence, in close vicinity of the human wearer surface. Typically, wearable antennas are worn in the vicinity of arms, legs, chest, or back of the human... 

In this section, we summarize and describe some of the most recently developed wearable textile antennas. Each of the described antennas possesses features that provide solutions to one or more of the adverse effects and challenges described in the previous section. 

With respect to other ISM frequency bands, the 5.8 GHz ISM band ([5.725, 5.875] GHz) has received relatively less attention from the research community. Fewer contributors have proposed, to date, wearable textile antennas operating only in the... 

Wearable textile antennas are particularly convenient for satellite communications. For example, a useful application involves the coordination of activities by a group of rescue workers in operation. Each person may be equipped with a wearable textile system in which a textile antenna connects to a positioning satellite system, such as GPS, Galileo, or the Global Navigation Satellite System (GNSS). By means of such antennas, each rescue worker can acquire information about his/her position, which can be forwarded to the base station that keeps track of the positions and allows optimal coordination of the team s activity. 

R. Moro, S. Agneessens, H. Rogier, M. Bozzi, Wearable textile antenna in substrate integrated waveguide technology. Electron. Lett. 48 (16) (August 2012) 985—987. 

S. Zhu, R. Langley, Dual-band wearable textile antenna on an EBG substrate, IEEE Trans. Antenn. Propag. 57 (4) (April 2009) 926—935. 

Figure 10 0 Wearable textile antenna sewn on a cotton shirt, and measured radiation patterns of the textile and copper antennas at 600 MHz for different on-body locations (Wang et al.,...

Figure 10.26 Wearable textile antenna system for body-worn cellular communications. We note that the relationship between signal bars and actual power is as follows 1-bar —100 to -95 dBm 4-bar —85 to —80 dBm 6-bar -75 to —70 dBm and 7-bar > — 70 dBm. From Wang et al. (2014), 2014 IEEE.

M Klemm, I Locher, and G Troster, A novel circularly polarized textile antenna for wearable applications , 34 European Microwave Conference (EuMC), 11-14,2004. 

For textile antennas without a ground plane, the presence of the human body produces substantial effects on the antenna performance because it acts as an absorber for the radiated field and represents an additional loading. This mainly alters the antenna input impedance and efficiency. Radiation patterns also change with respect to the free-space situation the human body acts as a lossy reflector, making the radiation pattern more directional in the off-body direction. An example of such a behavior, on a wearable antenna without ground plane, is shown in Fig. 26.5, where the on-body and free-space horizontal pattern of a wearable UWB monopole antenna on a polyi-mide substrate (realized by the EM group of Ghent University), are compared. 

Antenna bending represents another very important adverse effect to be taken into account when designing and analyzing wearable antennas. Since a textile antenna... 

For wearable systems, including textile antennas, power efficiency represents a crucial matter, especially for the so-called autonomous systems, where the necessary power for the system operation is ideally obtained entirely by means of energy harvesting [16] from the surrounding environment, and no additional power supply is needed. Even in the case of wearable systems equipped with wearable battery units, it is very important to keep power consumption as low as possible. To this aim, several techniques were recently envisaged, by means of innovative textile antennas, such as active antennas as well as the use of multiantenna-processing techniques, such as diversity with multiple wearable antennas. 

Industrial, scientific, and medical bands are reserved portions of the radio spectrum, defined by the ITU Radio Regulations [23], that are employed in body-centric wireless communication applications and, more in general, for other industrial, medical, and scientific applications. The majority of textile antennas developed to date are intended for operation in some of those ISM bands, especially in the 2.45 GHz, by far the most popular for wearable antennas, and 5.8 GHz bands. The first band represents a good trade-off between antenna dimensions (inversely proportional to fiequency) and path loss (increasing with frequency), whereas the second is more convenient when... 

Figure 26.10 Realized prototype of wearable textile GPS antenna.

S. Chen, T. Kaufmann, C. Fumeaux, Wearable textile microstrip patch antenna for multiple ISM band communications, in 2013 IEEE Antennas and Propagation Society International Symposium (APSURSI), 2013. 

In this chapter, we describe the background and design rules for embroidered textile antennas. Characterization of the embroidered textiles at RF is provided, and several example textile designs are presented and tested for applications related to wearable RF electronics, medical monitoring, and radio frequency identification (RFID). 

From Sankaralingam, S., Gupta, B., 2010. Development of textile antennas for body wearable applications and investigations on their performance under bent conditions. Prog. Electromagn. Res. B 22, 53-71. 

Giddens, H., et al., 2012. Influence of body proximity on the efficiency of a wearable textile patch antenna. In 2012 6th European Conference on Antennas and Propagation (EUCAP), pp. 1353-1357. 

Tudor, J., et al., 2013. Inkjet printed dipole antennas on textiles for wearable communications. 

E-textiles may be defined as textiles with electronic properties, and the markets for E-textiles are rapidly growing. An E-textile is an application built within a textile. E-textiles are finding their use in wearable technology, sports and fitness markets, medical and health monitoring systems, sleep apnea monitoring systems, antenna applications, space, military, infotainment, fashion, and others. Conductive tapes, webbings, fabrics, and 3D preforms are being used for E-textile applications. E-textile markets will soon be a billion dollar industry. 

E-textiles are being used in wearable technology, the sports and fitness market, health monitoring systems, sleep apnea monitoring systems, antenna applications, and space, defense, and military applications. 

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