Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications. By Christophe Caloz and Tatsuo Itoh.

This paper presents a novel broadband rectenna for ambient wireless energy harvesting over the frequency band from 1.8 to 2.5 GHz. First of all, the characteristics of the ambient radio-frequency energy are studied. The results are then used to aid the design of a new rectenna. A novel two-branch impedance matching circuit is introduced to enhance the performance and efficiency of the rectenna at a relatively low ambient input power level. A novel broadband dual-polarized cross-dipole antenna is proposed which has embedded harmonic rejection property and can reject the second and third harmonics to further improve the rectenna efficiency. The measured power sensitivity of this design is down to $- {\bf 35}\;{\bf dBm}$ and the conversion efficiency reaches 55% when the input power to the rectifier is $- {\bf 10}\;{\bf dBm}$ . It is demonstrated that the output power from the proposed rectenna is higher than the other published designs with a similar antenna size under the same ambient condition. The proposed broadband rectenna could be used to power many low-power electronic devices and sensors and found a range of potential applications.

A High-Efficiency Broadband Rectenna for Ambient Wireless Energy Harvesting

Energy harvesting (EH) from ambient radio-frequency (RF) electromagnetic waves is an efficient solution for fully autonomous and sustainable communication networks. Most of the related works presented in the literature are based on specific (and small-scale) network structures, which although give useful insights on the potential benefits of the RF-EH technology, cannot characterize the performance of general networks. In this paper, we adopt a large-scale approach of the RF-EH technology and we characterize the performance of a network with random number of transmitter-receiver pairs by using stochastic-geometry tools. Specifically, we analyze the outage probability performance and the average harvested energy, when receivers employ power splitting (PS) technique for "simultaneous" information and energy transfer. A non-cooperative scheme, where information/energy are conveyed only via direct links, is firstly considered and the outage performance of the system as well as the average harvested energy are derived in closed form in function of the power splitting. For this protocol, an interesting optimization problem which minimizes the transmitted power under outage probability and harvesting constraints, is formulated and solved in closed form. In addition, we study a cooperative protocol where sources' transmissions are supported by a random number of potential relays that are randomly distributed into the network. In this case, information/energy can be received at each destination via two independent and orthogonal paths (in case of relaying). We characterize both performance metrics, when a selection combining scheme is applied at the receivers and a single relay is randomly selected for cooperative diversity.

/pdf/simultaneous-information-and-energy-transfer-in-large-scale-11857a8bvk.pdf

Simultaneous Information and Energy Transfer in Large-Scale Networks with/without Relaying

This paper introduces a novel compact ultralightweight multiband RF energy harvester fabricated on a paper substrate. The proposed rectenna is designed to operate in all recently released LTE bands (range 0.79–0.96 GHz; 1.71–2.17 GHz; and 2.5–2.69 GHz). High compactness and ease of integration between antenna and rectifier are achieved by using a topology of nested annular slots. The proposed rectifier features an RF-to-dc conversion efficiency in the range of 5%–16% for an available input power of −20 dBm in all bands of interest, which increases up to 11%–30% at −15 dBm. The rectenna has been finally tested both in laboratory and in realistic scenarios featuring a superior performance to other state-of-the-art RF harvesters on flexible substrates.

A Novel Ultra-Lightweight Multiband Rectenna on Paper for RF Energy Harvesting in the Next Generation LTE Bands

In this paper, a rigorous procedure for the circuit-level analysis and design of entire systems, developed to provide power wirelessly, is presented. A unified theoretical approach is first introduced, based on a two-port-equivalent circuit representation, to describe the wireless power transfer link when the transmitter and the receiver are either in the near-field or in the far-field region reciprocally. This approach allows one to compute in a straightforward manner the system figure of merit, namely the power transfer efficiency. Specific guidelines for the two configurations are then intensively discussed together with the adopted software tools based on the combination of full-wave analysis and nonlinear harmonic balance techniques. Several practical examples based on this design procedure are presented, demonstrating predicted and experimental behavior of unconventional devices for both near-field and far-field power transfer usage.

Electromagnetic Energy Harvesting and Wireless Power Transmission: A Unified Approach

A wearable rectenna for operation in the ultra high frequency (UHF) band is presented The proposed device consists of a compact patch antenna and a full-wave bridge rectifier, both fabricated with textile materials The patch antenna has been realized by using an adhesive conductive fabric on a bi-layer substrate made of pile and jeans As for the rectifier, it is on a layer of jeans on the back-face of the antenna Experimental data referring both to the patch antenna and to the rectenna are reported and discussed From measurements performed with an incident power density of 14 μ/cm2, it is demonstrated that the rectenna here presented exhibits a conversion efficiency higher than 20% over the frequency range 860-918 MHz with a maximum of about 50% at 876 MHz

UHF Wearable Rectenna on Textile Materials

This article provides a few practical guidelines for designing wearable antennas. A crucial requirement for this kind of antenna is to be noninvasive and "invisible" to the final user. To this end, an application-centered approach is required for both the design and the fabrication process, which leads to high cost, thereby limiting the large-scale production of wearable antennas. Accordingly, this article pays particular attention to low-cost and time-saving fabrication techniques that distinguish between nontextile and fully textile antennas.

Wearable Antennas: Nontextile Versus Fully Textile Solutions

Remote monitoring of the elderly in telehealth applications requires that the monitoring must not affect the elderly’s regular habits. To ensure this requirement, the components (i.e., sensor and antenna) necessary to carry out such monitoring should blend in with the elderly’s daily routine. To this end, an effective strategy relies on employing wearable antennas that can be fully integrated with clothes and that can be used for remotely transmitting/receiving the sensor data. Starting from these considerations, in this work, two different methods for wearable antenna fabrication are described in detail: the first resorts to the combined use of nonwoven conductive fabrics and of a cutting plotter for shaping the fabric, whereas the second considered fabrication method resorts to the embroidery of conductive threads. To demonstrate the suitability of the considered fabrication techniques and to highlight their pros and cons, numerical and experimental results related to different wearable antennas are also reported and commented on. Results demonstrate that the presented fabrication techniques and strategies are very flexible and can be used to obtain low-cost wearable antennas with performance tailored for the specific application at hand.

/pdf/wearable-antennas-for-remote-health-care-monitoring-systems-4ya1k2dl6o.pdf

Wearable Antennas for Remote Health Care Monitoring Systems

This study presents a wearable antenna for a global positioning system–global system for mobile communication (GPS–GSM)-based anti-theft tracking system to be embedded in high-cost clothing and luggage accessories (such as leather bags). To assess the feasibility of this solution, a prototype antenna was designed mimicking the shape of one of the Levi Strauss & Co.’s logos, and it was fabricated using a conductive non-woven fabric on a layer of leather. Furthermore, to cover both the GPS L1 and the GSM-1800 bands with a single radiating element, positive-intrinsic-negative (PIN) diodes were employed to reconfigure the operating frequency of the antenna. Experimental data demonstrating the feasibility of the proposed design strategy are presented and discussed.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2015.0774

Wearable logo-antenna for GPS–GSM-based tracking systems

A reconfigurable patch antenna consisting of a square patch with two cross-shaped diagonal slots is presented. The proposed design approach is based on the use of two pairs of switches in order to obtain both frequency and polarization reconfigurability. Specifically, three different polarization states have been obtained: a Right-Hand Circular Polarization, a Left-Hand Circular Polarization and a Linear Polarization. Experimental results, referred to a realization on a FR4 substrate of the layouts corresponding to the useful switch configurations, are reported.

https://www.jpier.org/pierc/pierc09/02.09061505.pdf

Laura Corchia

Papers

UHF Wearable Rectenna on Textile Materials

Wearable Antennas: Nontextile Versus Fully Textile Solutions

Wearable Antennas for Remote Health Care Monitoring Systems

Wearable logo-antenna for GPS–GSM-based tracking systems

Patch Antenna with Reconfigurable Polarization