Substrate integrated waveguide textile antennas as energy harvesting platforms

Textile multi-antenna systems are key components of smart fabric and interactive textile (SFIT) systems, as they establish reliable and energy-efficient wireless body-centric communication links. In this work, we investigate how their functionality can further be extended by exploiting their surface as an energy harvesting and power management platform. We provide guidelines for selecting an appropriate antenna topology and describe a suitable integration procedure. We demonstrate this approach by integrating two flexible solar cells, a micro-energy cell and a flexible power management system onto a well-chosen wearable substrate integrated waveguide cavity-backed textile slot antenna, without affecting its performance, to enable energy harvesting from solar and artificial light. In addition, the compact and highly-integrated harvesting module provides a terminal for connecting a thermoelectric generator, enabling thermal body energy harvesting. Measurements in a realistic indoor environment have demonstrated that this hybrid energy harvesting approach leverages a more continuous flow of scavenged energy, enabling energy scavenging in most of the indoor and outdoor scenarios

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

Dual-band substrate integrated waveguide textile antenna with integrated solar harvester

A dual-band wearable textile antenna based on substrate integrated waveguide technology is presented for operation in the [2.4-2.4835]-GHz Industrial, Scientific and Medical band and the [2.5-2.69]-GHz 4G LTE band 7. The antenna features an integrated flexible solar harvesting system, consisting of a flexible solar cell, a power management system, and energy storage. All these components are judiciously positioned on the antenna platform in order not to affect its radiation performance. The measured reflection coefficients and radiation characteristics after bending and deploying the antenna on a human body prove that the antenna is well suited for on-body use. A measured on-body antenna gain and radiation efficiency of 5.0 dBi and 89% are realized. Measurements in a real-life situation have demonstrated the ability to scavenge a maximum of 53 mW by means of a single integrated flexible solar cell

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

Dual-polarized 28-GHz air-filled SIW phased antenna array for next-generation cellular systems

A high-performance dual-polarized eight-element air-filled substrate-integrated-waveguide (AFSIW) cavity-backed patch antenna array is presented. The antenna operates in the [26.5-29.5] GHz band and provides a stable high data-rate wireless communication link between end-user terminals and access points in next-generation cellular systems. Its topology is carefully selected to maximize the performance of the array. In addition, by combining the AFSIW technology with a new antenna architecture, a low-profile, low-cost, stable, and high-performance array design is guaranteed. A prototype was fabricated and validated, demonstrating a wide active impedance bandwidth over ±35 o scanning range and low-cross polarization level within the entire frequency band

Textile SIW antennas as hybrid energy harvesting and power management platforms

A compact, highly-integrated and unobtrusive wearable textile antenna system, able to establish a reliable and energy-efficient wireless body-centric communication link in the [2.4-2.4835]-GHz Industrial, Scientific and Medical band and enabling energy harvesting from three different energy sources, is presented. Our design approach relies on further extending the functionality of a carefully selected textile antenna by exploiting its surface as an energy scavenging and power management platform. More specific, two different ultra-flexible solar cells, a micro-energy cell and a flexible power management system are integrated onto a wearable substrate integrated waveguide cavity-backed textile slot antenna to enable energy harvesting from both solar and artificial light. Furthermore, thermal body energy harvesting, via an externally connected thermoelectric generator, is enabled by including an ultra-low voltage step-up converter. Measurements in four well-chosen indoor scenarios demonstrate that a hybrid energy-harvesting approach is necessary to obtain a more continuous flow and a higher amount of scavenged energy, leading to a higher system autonomy and/or reduced battery size

Recent advances in materials and technologies for body-centric and IoT antenna systems

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Ultra-wideband cork substrate-integrated-waveguide cavity-backed slot antenna

An ultra-wideband (UWB) substrate-integrated-waveguide (SIW) cavity-backed slot antenna covering the lower part of the 3.1-10.6 GHz block allocated to UWB transmission systems, being 3.1-3.6 GHz, is designed, constructed and validated. Owing to its planar topology, low profile and the use of cork substrate material, the proposed antenna may be integrated unobtrusively in any cork surface. Prior to the antenna design, the cork substrate material was characterized in the frequency band of interest. The design is conducted based on the average properties, while maintaining some impedance bandwidth margins to allow for varying cork material properties. A prototype is validated in free space conditions, confirming the high performance observed in simulation. An impedance bandwidth of 700 MHz (20.9%) is measured. At the center frequency 3.35 GHz, a radiation efficiency of 78%, a front-to-back ratio of 17.2 dB, and a maximum gain of 4.9 dBi are obtained. The maximum gain varies only by 1.4 dB within the frequency band of interest. The other far-field properties also vary only negligibly, which is the most important requirement to UWB antennas