Wearable textile antennas are now available for many different operating frequencies, ranging from lower UHF bands to the most recent millimeter-wave band of 60 GHz. This enables the fabrication of more robust, comfortable, and seamless antenna structures. During the last decade, wearable antennas technology has evolved from simple rectangular patch narrowband antennas, to more complex topologies for the radiating element, with broadband characteristics, as well as new materials and promising technological solutions. In this chapter, an overview of some representative state-of-the-art wearable textile antennas is presented, based on the frequency range in which they operate. Rogier, in Smart Textiles and their Applications, 2016 26.5 Conclusions and future outlook This increase in dimension of the patch along its path, and denoted by Δ L, is a function of the effective dielectric constant ε eff and the ratio W/ h as It is because of these fringing fields that the patch looks electrically greater than its physical dimension. The electric field radiates along the z axis, whereas the magnetic field is present in the x, y plane. These field extensions are known as fringing fields. Note, however, that the electric fields do not end immediately at the patch's edges but rather extend somewhat to the outer periphery of the patch. The polarization of the field interestingly enough depends on the instantaneous phase of the applied signal. The electric field is zero at the center of the patch and progresses to become maximum positive on one side and maximum negative on the opposite side. The distribution of the electric field of a rectangular patch when excited in its fundamental mode is also shown. A basic patch antenna is depicted in Figure 1.42. At this point it is important to elaborate on ε eff in Eqn (1.185).
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