Circularly-polarised cavity-backed wearable antenna in SIW technology

This study presents a circularly-polarised substrate-integrated waveguide (SIW) antenna implemented using a textile substrate and operating at 2.45GHz, in the industrial, scientific, and medical frequency band. The antenna topology is based on a folded cavity with an annular ring as a radiating element, and it permits to obtain compact size and low sensitivity to the environment, without deteriorating the radiating performance. These characteristics, together with the choice of adopting a textile substrate, make the SIW antenna suitable for the integration in wearable systems for body-centric applications. The electromagnetic performance of the proposed antenna achieved in simulations was verified through the measurement of the device in an anechoic chamber. The circularly-polarised antenna exhibits a maximum gain of 6.5dBi, a radiation efficiency of 73% and a very high front-to-back ratio

Wearable, small, and robust: the circular quarter-mode textile antenna

A miniaturized wearable antenna, entirely implemented in textile materials, is proposed that relies on a quarter-mode substrate integrated waveguide topology. The design combines compact dimensions with high body-antenna isolation, making it excellently suited for off-body communication in wearable electronics/smart textile applications. The fabricated antenna achieves stable on-body performance. A measured on-body impedance matching bandwidth of 5.1% is obtained, versus 4.8% in free space. The antenna gain equals 3.8 dBi in the on-body and 4.2 dBi for the free-space scenario. High radiation efficiency, measured to be 81% in free space, is combined with a low calculated specific absorption rate of 0.45 mW/g, averaged over 1 g of tissue, with 500 mW input power

Coupled eighth-mode substrate integrated waveguide antenna: small and wideband with high-body antenna isolation

A novel antenna design for wideband operation is presented, consisting of a system of two coupled miniaturized eighth-mode resonant radiating cavities with a low-complexity feeding network. The design methodology relies on the virtual magnetic boundaries along the symmetry planes of a rectangular waveguide resonator, for size reduction, and the frequency bifurcation of two tightly coupled resonators, for bandwidth enhancement. After discussing its operating principle, a prototype targeting wearable applications is designed, manufactured, and validated. Multiband operation is achieved with simultaneous coverage of the 2.4-GHz ISM band and the LTE-7 up- and downlink-bands. Measurements in free-space and on-body scenarios validate the antenna's performance. A bandwidth of 414 MHz (16.2%) is measured, as well as a maximal gain of 4.7 dBi. The directive patch-like radiation pattern and the ground plane topology lead to high body-antenna isolation and good on-body performance. Impedance bandwidth and radiation pattern remain stable when the antenna is worn by a person and bent around a cylinder to mimic deformation

Robust, wearable, on-body antenna relying on half mode substrate integrated waveguide techniques

A compact, robust, wearable antenna for body-worn applications in the 2.4 GHz Industrial Medical and Scientific band is designed, fabricated and tested. This novel compact textile cavity backed slot antenna combines a half-mode substrate integrated waveguide topology with an additional row of shorting vias for miniaturization. Excellent free space performance is achieved with a measured 4.6 % impedance bandwidth, maximal gain of 4.7 dBi and radiation efficiency of 81.3 %. On-body measurements reveal minimal frequency detuning when the antenna is worn by a test subject as well as a negligible impedance bandwidth reduction to 4.5 %. The low calculated Specific Absorption Rate of 0.51 W/kg averaged over 1 g of tissue demonstrates high antenna body isolation. Therefore, this design is an attractive option as antenna in smart textile systems

Compact cavity-backed antenna on textile in substrate integrated waveguide (SIW) technology

In this paper a folded cavity-backed patch antenna implemented in substrate integrated waveguide (SIW) technology is presented. The antenna has been designed to operate at 2.45 GHz, in the industrial, scientific and medical (ISM) frequency band, and a textile substrate has been adopted for the realization of the component. This topology of textile antenna could be useful for the monitoring of the activities of rescue workers in emergency situations such as the localization of firefighters, and the communication in critical operations. The proposed antenna has been experimentally verified: the response of the antenna exhibits a small frequency shift, caused by a discrepancy between the nominal and the real value of electrical permittivity of the textile substrate. The measured radiation characteristics of the antenna show a good agreement with simulations, and a measured radiation efficiency of approximately 70%

The next generation textile antennas based on substrate integrated waveguide technology

Textile antennas for body-worn applications have some very specific requirements and needs. From an electrical engineer's point of view, good radiation characteristics and impedance matching to the active electronics are important. From the wearer's perspective, the antenna should be unobtrusively integrated into the clothing, and the smart textile comfortable to wear. New techniques offer the potential to fulfill these different needs. One new approach consists of applying metalized eyelets to implement substrate integrated waveguide technology on textile materials. This results in high-performance on-body antennas with excellent behavior in close proximity of the human body. Two realizations are discussed: a wideband design and a miniaturized half mode substrate integrated waveguide dual-band design. Both yield excellent free-space and on-body performance, and superb antenna-body isolation, automatically resulting in very robust characteristics when deployed on-body

Environmental electromagnetic characterization framework for wearable antenna materials

In wearable antenna design, the prevailing atmospheric conditions can have a significant effect on the electromagnetic properties of the fabric substrate and hence the resulting antenna performances. Therefore, an accurate characterization of this effect is an important issue in textile antenna design. This paper presents a dedicated constitutive parameter extraction method as a function of relative humidity of all materials used. The method relies on a comparison between measured and simulated antenna figure's of merit in order to extract complex permittivity of the substrate and effective bulk conductivity of the e-textile. A two-step approach is used for separating conductor losses from substrate losses. The problem of finding the best fit between simulated and measured data is solved by relying on a surrogate based optimization technique. Here, two fabric materials are characterized for relative humidity levels ranging from 10% to 90%