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- Smart environment technology as a possible enabler of smart citiesPublication . Gonçalves, Ricardo; Carvalho, Nuno Borges; Pinho, Pedro; Roselli, LucaThis paper discusses the technology of smart floors as a enabler of smart cities. The discussion will be based on technology that is embedded into the environment that enable location, navigation but also wireless power transmission for powering up elements siting on it, typically mobile devices. One of those examples is the smart floor, this implementation follows two paths, one where the floor is passive, and normally passive RFID's are embedded into the floor, they are used to provide intelligence into the surrounding space, this is normally complemented with a battery powered mobile unit that scans the floor for the sensors and communicates the information to a database which locates the mobile device in the environment. The other path for the smart city enabler is where the floor is active and delivers energy for the objects standing on top of it. In this paper these two approaches will be presented, by discussing the technology behind it. © 2014 IEEE.
- 3D antenna characterization for WPT applicationsPublication . Jordão, Marina; Pires, Diogo; Belo, Daniel; Pinho, Pedro; Carvalho, Nuno BorgesThe main goal of this paper is to present a three-dimensional (3D) antenna array to improve the performance of wireless power transmission (WPT) systems, as well as its characterization with over-the-air (OTA) multi-sine techniques. The 3D antenna consists of 15 antenna elements attached to an alternative 3D structure, allowing energy to be transmitted to all azimuth directions at different elevation angles without moving. The OTA multi-sine characterization technique was first utilized to identify issues in antenna arrays. However, in this work, the technique is used to identify which elements of the 3D antenna should operate to transmit the energy in a specific direction. Besides, the 3D antenna design description and its characterization are performed to authenticate its operation. Since 3D antennas are an advantage in WPT applications, the antenna is evaluated in a real WPT scenario to power an RF-DC converter, and experimental results are presented.
- Challenges in resource-constrained IoT devices: energy and communication as critical success factors for future IoT deploymentPublication . Pereira, Felisberto; Correia, Ricardo; Pinho, Pedro; Lopes, Sérgio I.; Carvalho, Nuno BorgesInternet of Things (IoT) has been developing to become a free exchange of useful information between multiple real-world devices. Already spread all over the world in the most varied forms and applications, IoT devices need to overcome a series of challenges to respond to the new requirements and demands. The main focus of this manuscript is to establish good practices for the design of IoT devices (i.e., smart devices) with a focus on two main design challenges: power and connectivity. It groups IoT devices in passive, semi-passive, and active, giving details on multiple research topics. Backscatter communication, Wireless Power Transfer (WPT), Energy Harvesting (EH), chipless devices, Simultaneous Wireless Information and Power Transfer (SWIPT), and Wake-Up Radio (WUR) are some examples of the technologies that will be explored in this work.
- Pentagonal parch-excited sectorized antenna for localization systemsPublication . Brás, Luís; Carvalho, Nuno Borges; Pinho, PedroA pentagonal patch-excited sectorized antenna (SA) suitable for 2.4-2.5 GHz localization systems was studied and developed. The integration of six patch-excited structures converges into a sectorized antenna called Hive5 that provides gain improvement compared to a patch antenna, maximum variation of 3 dB beam width over the radiation pattern and circular polarization (CP). This antenna is presented and analyzed taking into account the tap length and the flare angle. The proposed antenna in combination with a RF-Switch provides a cost effective solution for localization based on Wireless Sensor Networks (WSN) and will be used for implementing angle of arrival (AoA) techniques combined with RF fingerprinting techniques.
- RFID-based wireless passive sensors utilizing cork materialsPublication . Gonçalves, Ricardo; Rima, Sergi; Magueta, Roberto; Pinho, Pedro; Collado, Ana; Georgiadis, Apostolos; Hester, Jimmy; Carvalho, Nuno Borges; Tentzeris, Manos M.This paper presents the design of low-cost, conformal UHF antennas and RFID tags on two types of cork substrates: 1) natural cork and 2) agglomerate cork. Such RFID tags find an application in wine bottle and barrel identification, and in addition, they are suitable for numerous antenna-based sensing applications. This paper includes the high-frequency characterization of the selected cork substrates considering the anisotropic behavior of such materials. In addition, the variation of their permittivity values as a function of the humidity is also verified. As a proof-of-concept demonstration, three conformal RFID tags have been implemented on cork, and their performance has been evaluated using both a commercial Alien ALR8800 reader and an in-house measurement setup. The reading of all tags has been checked, and a satisfactory performance has been verified, with reading ranges spanning from 0.3 to 6 m. In addition, this paper discusses how inkjet printing can be applied to cork surfaces, and an RFID tag printed on cork is used as a humidity sensor. Its performance is tested under different humidity conditions, and a good range in excess of 3 m has been achieved, allied to a good sensitivity obtained with a shift of >5 dB in threshold power of the tag for different humid conditions.
- Design and evaluation of multi-band RF energy harvesting circuits and antennas for WSNsPublication . Borges, Luís M.; Barroca, Norberto; Saraiva, Henrique M.; Tavares, Jorge; Gouveia, Paulo T.; Velez, Fernando J.; Loss, Caroline; Salvado, Rita; Pinho, Pedro; Gonçalves, Ricardo; Carvalho, Nuno Borges; Chavez-Santiago, Raúl; Balasingham, IlangkoRadio frequency (RF) energy harvesting is an emerging technology that will enable to drive the next generation of wireless sensor networks (WSNs) without the need of using batteries. In this paper, we present RF energy harvesting circuits specifically developed for GSM bands (900/1800) and a wearable dual-band antenna suitable for possible implementation within clothes for body worn applications. Besides, we address the development and experimental characterization of three different prototypes of a five-stage Dickson voltage multiplier (with match impedance circuit) responsible for harvesting the RF energy. Different printed circuit board (PCB) fabrication techniques to produce the prototypes result in different values of conversion efficiency. Therefore, we conclude that if the PCB fabrication is achieved by means of a rigorous control in the photo-positive method and chemical bath procedure applied to the PCB it allows for attaining better values for the conversion efficiency. All three prototypes (1, 2 and 3) can power supply the IRIS sensor node for RF received powers of -4 dBm, -6 dBm and -5 dBm, and conversion efficiencies of 20, 32 and 26%, respectively. © 2014 IEEE.
- RFID passive tag antenna for cork bottle stopperPublication . Gonçalves, Ricardo; Magueta, Roberto; Pinho, Pedro; Carvalho, Nuno BorgesIn this paper we propose a possible design for a RFID tag antenna embedded into cork. The antenna is small and conformal and intended to be used into bottle stoppers for tracking and logging purposes of wine or other beverages. The proposed design is based on an inductive ring and an added resistance in order to modify the current distributions of the antenna. The resulting antenna has a relatively directive radiation pattern and despite the small efficiency it is able to operate with a commercial RFID reader at a reasonable distance. © 2014 IEEE.
- RFID Tattoo for COVID-19 Temperature MeasuringPublication . Silveira, Tagleorge; Pinho, Pedro; Carvalho, Nuno BorgesIn order to assist in the screening and monitoring of possible infected by COVID-19, whose fever is one of the initial symptoms, a RFID tattoo tag for human monitoring was developed. The prototype of the tattoo tag presented proved to be effective in measuring human body temperature from 36° to 40° C, thus being a viable option for large-scale screening and analysis, and for being made with aluminum foil and school adhesive tape. That when using these materials, it presents itself as a disposable device, of low cost, durable, and operable in the RFID UHF frequency range.
- UHF RFID tag antenna for bottle labelingPublication . Gonçalves, Ricardo; Carvalho, Nuno Borges; Magueta, Roberto; Duarte, Alcídia; Pinho, PedroIn this paper we present a possible design for a passive RFID tag antenna on paper substrate to be integrated into bottle labels. Considering the application scenario, we verified and determined the permittivity and dissipation factor of the materials in order to simulate all the possible sources that would influence the antenna performance. The measured results reported a maximum reading range of 1.45 m even though the efficiency obtained with the antenna integrated into the bottle was only of 3%. © 2014 IEEE.
- Humidity passive sensors based on UHF RFID using cork dielectric slabsPublication . Gonçalves, Ricardo; Pinho, Pedro; Carvalho, Nuno Borges; Tentzeris, Manos M.In this paper we show the design of passive UHF RFID tag antenna on cork substrate. Due to the cork sensitivity to humidity changes, we can use the developed sensor to sense changes in the relative humidity of the environment, without the need for batteries. The antenna is built using inkjet printing technology, which allows a good accuracy of the design manufacturing. The sensor proved usable for humidity changes detection with a variation of threshold power from 11 to 15 dB between 60 and near 100% humidity levels. Presenting, therefore, reading ranges between 3 to 5 meters. © 2015 EurAAP.