Textile patch antenna

L. Vallozzi, H. Rogier, C. Hertleer, Dual polarized textile patch antenna for integration into protective garments, IEEE Antenn. Wireless Propag. Lett. 7 (2008) 440—443. 

Figure 10.17 Textile patch antenna and its RF performances (a) on a planar surface and (b) mounted on a cylindrical surface.

Vallozzi, L., Rogier, H., Hertleer, C., 2009. A textile patch antenna with dual polarization for rescue workers garments. In Presented at European Conference on Antennas Propagation, Berlin, Germany. 

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. 

Locher, L, et al., 2006. Design and characterization of purely textile patch antennas. IEEE Trans. Adv. Pack. 29 (4), 777-788. 

Top view of 3D woven E-textile antenna is shown in Eigure 9.6. Conductive patch of stainless steel and U-shaped slot are shown at the top. The challenge inherent to many advanced communication and navigation application is achieving wideband operation from a single antenna. One such antenna architecture that is capable of achieving the types of bandwidth required is the slotted patch antenna. This antenna used a thick substrate ( 1.5 cm) and the U-shaped slot to increase the bandwidth. 

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. 

Basically, textile antennas can be subdivided into two categories, those having a ground plane (such as patch antennas) and those without (such as UWB dipoles). In the first case, the effect on performance is very small, since the ground plane acts as an electric shield between the radiating elements of the antenna and the human body. 

F. Boeykens, L. Vallozzi, H. Rogier, Cylindrical bending of deformable textile rectangular patch antennas, Int. J. Antenn. Propag. (2012) 11. 

K. Koski, E. Lohan, L. Sydanheimo, L. Ukkonen, Y. Rahmat-Samii, Electro-textile UHE RFID patch antennas for positioning and localization applications, in IEEE RFID Technology and Applications Conference (RFID-TA), September 2014. 

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. 

Figure 10.6 Various fabricated RF patterns using textiles on PDMS substrate textile transmission Une, patch antennas, and spiral antenna.

To demonstrate the RF performance of textile antennas, sample patch antennas are fabricated for experimental verification on both planar and curved surfaces (Wang et al., 2012b). Measurements showed that the RF performance of the E-fiber patch antennas on polymer substrate is as good as that of their copper counterparts. 

In traditional microwave systems antennae are fabricated on rigid substrates, as wires or as hollow structures. Antennae on textiles have been demonstrated earlier but only with limited design variations, mainly as microstrip patch or slot antennae. There is a need to explore different structures especially in view of multi-fiequency or wideband operation. 

Figure 9.7 shows a conductive layer of stainless steel on face of lower spacer of E-textile antenna. This E-textile antenna was woven with Quartz fiber spacers, conductive stainless steel, conductive stripline, and conductive patch with Quartz fiber. 

Textile antennae can be incorporated into clothing systems for long-distance communication (Salonen and Rahmat-Samii, 2006). They can be directly printed onto a textile substrate or a micro-patch anteima attached to a vest. Depending on the environment, such antennae can operate in the range of 10-100 m. Longer-distance communication can be achieved by improved technology and the use of laptop computers or mobile phones. Very short distance connections can be made by wireless links using induction. Data can also be transferred by Bluetooth modules if the soldiers are located close to a central control facility. 

A microstrip patch is a representative candidate for a wearable integration, because it can be thin, lightweight, low maintenance, robust, and easily integrated into a garment and coupled with RF circuits (Wang et al., 2012). Moreover, the conductive textile used for antenna purposes has to have a low and stable electrical resistivity (<10/sq.) to minimize losses (Locher et al., 2006). Several properties of the materials can influence the behavior of the antenna properties. For instance, the permittivity and the thickness of the substrate change the bandwidth and the efficiency of a planar microstrip antenna (Liu et al., 2011). In general, fabrics present a complex structure, in term of density of fibers and hence air volume and size of the pores, which allow a very low dielectric constant with a reduction of the surface wave losses and an increase of the impedance bandwidth. 

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