Planar inverted-F antennas (PIFAs) made of woven conductive textiles and of patterns embroidered with conductive threads are investigated. The influence of conductive thread density on antenna properties is considered in both cases. The effect of lockstitch on antenna resonant frequency is quantified. A metallic button is proposed as the transition between textile antennas and classical circuits. A full-textile prototype of a PIFA is designed and shown to operate properly in the ISM 2.4 band.

Uniaxial multilayer cylinder cloaks have recently been proposed to prevent scattering of electromagnetic waves. These cloaks are based on spatial variation of constitutive parameters within the structure by means of metamaterials. A mathematical description of invisibility in such cloaks is provided. The analysis approach is based on modal analysis of cylindrical multilayer structures. In order to analyze structures with arbitrary number of layers, an algorithm to calculate spectral-domain Green's functions of uniaxial multilayer structures has been developed. The results show that the recently introduced metamaterial cloaks with reduced variation of constitutive parameters can decrease the total scattering width up to a factor of three, but only in a narrow frequency band due to dispersion in the filling material. Furthermore, it is shown that in the analyzed structures already 6 layers of constant permittivity and permeability approximate well the continuous dependence of constitutive parameters.

Uniaxial cylindrical cloaks have recently been proposed to prevent scattering of electromagnetic waves, i.e., to render objects invisible. While it is possible to achieve that the rays follow the proper path inside the cloak, the proposed cloaks with reduced variation of constitutive parameters suffer from nonzero reflectance. The purpose of this paper is to improve invisibility performance of the original cloak structure in terms of total scattering width reduction and the operating frequency bandwidth. Therefore, the program for analyzing uniaxial cylindrical structures is merged with the global optimization program based on the particle swarm optimization algorithm. The results show that it is possible either to obtain the “perfect” cloak at the expense of bandwidth or to improve the operating frequency bandwidth at the expense of limited reduction of total scattering width.

Slotted PIFA on the textile substrate suitable for body-centric applications in the UHF band is proposed. The influence of slot in the ground plane on the antenna parameters is theoretically investigated using simplified model of human body.

The electromagnetic wave propagation around human body torso is modelled by considering elementary electric and magnetic dipoles over an infinite muscle-equivalent cylinder. The poles in the spectral domain Green’s function with smallest imaginary part are found to correspond to creeping wave propagation coefficients which predict the general trend in propagation around human body. In addition, it was found that axial magnetic field component is crucial for communication via creeping waves since it generates modes with smaller field decay compared to axial electric field. The developed model may thus serve as a practical guideline in design of on-body wearable antennas. The theoretical considerations are verified with simulations and measurements on the prototype of PIFA antenna placed on the human body.

This paper presents an energy harvesting device for body centric sensor systems. The focus of collecting energy is put in the sensor far-field and in a large frequency bandwidth. The proposed device comprises of the logarithmic spiral textile antenna paired with a simple rectifier circuit. The antenna is designed and manufactured by embroidered conductive yarn into denim material. The antenna prototype has been tested. Several rectifier circuit topologies were simulated and the DC voltage at the rectifier output is obtained by simulation.