WPT Related Applications Enabling Internet of Things Evolution

WPT Related Applications Enabling Internet of Things Evolution L. Roselli1 , C. Mariotti1 , M. Virili1 , F. Alimenti1 , G. Orecchini1 , V. Palazzi1 , P. Mezzanotte1 , N. B. Carvalho2 1 Department 2 Institute

of Engineering, University of Perugia, Perugia, Italy of Telecommunication, University of Aveiro, Aveiro, Portugal [email protected]

Abstract—Internet of Things (IoT) is becoming a driving paradigm for the Information and Communication Technology (ICT) evolution. This paradigm is not a revolution, yet is a way to look at, use and evolve existing technologies and apply them to new solutions. Among these technologies, Wireless Power Transmission (WPT) and related ones can be certainly considered enabling for IoT. WPT in fact, on the one hand is the core of Radio Frequency IDentification (RFID) systems, that represents likely the most promising physical layer communication platform for IoT; on the other hand WPT itself can be a means to power supply “things” and make them independent from grid connection and batteries, especially when massive localized concentration of granular devices can be envisaged, such as, for instance, in the case of “smart surface” implementation, “smart gravel” and so on. Example applications will be showed in this contribution in a comprehensive and holistic way, emphasizing the consistency of the developed technological solutions and architectures with short term and long term constraints and requirements for electronic apparatuses conceived for smart objects. Namely: data acquisition, wireless connectivity (short term), energy autonomy and object compatibility (long term).

I. I NTRODUCTION The revolution of wireless-ly connected “objects” began with the advent of the XXI century. In 2006 we started to have more connected devices than people on the planet. By 2020 we expect to connect 50 Billion of “objects”, that means more than 6 devices per person [1], [2]. This evolution is not only quantitative, but also related to the nature of the wireless systems: in fact, if since the beginning of the internet age, humans are responsible of uploading and sharing the information through PC, tablets, laptop and smartphone interfaces, nowadays we want the objects themselves to be able to sense and transmit the information autonomously, without humans’ intermediation. In order to achieve such an autonomy and integration with the environment, new hardware and software challenges have to be faced. At physical layer, the materials and manufacturing of the electronic devices have to be compatible with the production of the hosting objects in order to limit the impact on the cost and on the ambient compatibility of the end-product. The energy autonomy has to be guaranteed by adopting lowor zero- power architectures and exploiting Wireless Power Transmission (WPT) methods, thus avoiding batteries and cabled connections to the power grid. Finally, at communication

level, a huge amount of data has to be collected, processed, managed and made accessible to the user. This contribution aims to introduce suitable technology solutions related to the physical integrability and to energy autonomy of the wireless sensors. II. I OT E NABLING A RCHITECTURES Passive RFIDs seem to be the best candidates, so far, in order to ensure low- or zero-power consumption of the sensors and to use WPT and Energy Harvesting (EH) techniques to power supply the wireless nodes. Within standard passive RFIDs, normally composed by an IC and an antenna, an even more attractive approach for IoT applications, is that of chipless tags where the IC is removed and the sensed information or tags IDs are modulated and transmitted by exploiting various working principles [3]. An interesting chipless approach is that proposed in [4] and shown in Fig. 1: the reader interrogates at f0 and the tag responds at 2f0 , thus being immune to the carrier scattering signals. An example of 1-bit harmonic chipless tag is shown in Fig. 2(b).

Fig. 1: Harmonic tag working principle illustration. After [5].

III. I NTEGRATION T ECHNOLGIES AND M ATERIALS The physical layer is crucial for the effective integration of the electronics with any hosting object. Mechanical flexibility, high shape customization, recyclability and low fabrication processes and materials costs, are needed in order to enable the IoT. For these reasons, a particular attention is given by the scientific community, to the demonstration of substrate independent processes which make possible the application of the

(a)

Fig. 2: Example of 1-bit harmonic tag: received power by the reader at 2f0 versus distance. After [5].

devices on many materials, especially those not normally used in electronics [6]. Common substrate independent processes which fit the beforehand mentioned requirements are: inkjet printing [7], 3D printing, gravure printing, screen printing and metal adhesive laminate [8]. We report below an example of highly integrated Large Area Electronics (LAEs) into the environment, also known in literature as “energy evaporation”, where localization capabilities in conjunction with long- and short- range WPT functionalities are integrated together and embedded into the floors. Figure 3(a) shows the scheme of a distributed matrix of unit-cells composed by a 5.8 GHz patch antenna surrounded by a HF coil at 13.56 MHz. The patch is responsible of long range WPT while the coil has the double role of short range WPT source and localization through the connection with NFC tags. In Fig. 3(b) the performance of the unit-cell fabricated on top of a cork substrate are summarized demonstrating its feasibility even adopting a non-conventional material for electronics (but common in indoor environments). The fabrication is performed with the metal adhesive method [8].

IV. C ONCLUSION In summary, this paper is aimed to review some of the most suitable enabling technologies for the integration of wireless sensors nodes into everyday life objects, in a way that does not impact with the environment and with the end-products’ manufacturing costs and time. Particular attention is given to the energy autonomy aspects focusing on the suitable methods to wireless-ly empower electronics.

ACKNOWLEDGMENT The authors would thank the COST-WiPe action (IC1301) for its precious contribution in this work related to Wireless Power Transmission and other enabling technologies for Internet of Things applications.

(b)

Fig. 3: “Energy evaporation” (a) concept idea illustration and (b) performance of a unit-cell fabricated on cork. After [9].

R EFERENCES [1] cisco, “Internet of everything,” Cisco, Tech. Rep., 2015. [Online]. Available: http://ioeassessment.cisco.com/ [2] Verizon, “The Internet of Things 2015,” Verizon, Tech. Rep., 2015. [3] R. Nair, , E. Perret, and S. Tedjini, “Temporal multi-frequency encoding technique for chipless RFID applications,” in IEEE MTT-S International Microwave Symposium Digest, Montreal, QC, (Canada), Jun. 2012, pp. 1–3. [4] F. Alimenti and L. Roselli, “Theory of Zero-Power RFID Sensors Based on Harmonic Generation and Orthogonally Polarized Antennas,” Progress In Electromagnetics Research, vol. 134, pp. 337–357, 2013. [5] V. Palazzi, F. Alimenti, P. Mezzanotte, C. Mariotti, G. Orecchini, and L. Roselli, “Low-power frequency doubler in cellulose-based materials for harmonic RFID applications,” accepted for publication at Microwave and Wireless Components Letters (MWCL), vol. –, pp. –, 2014. [6] L. Roselli, N. Borges Carvalho, F. Alimenti, P. Mezzanotte, G. Orecchini, M. Virili, C. Mariotti, R. Goncalves, and P. Pinho, “Smart Surfaces: Large Area Electronics Systems for Internet of Things Enabled by Energy Harvesting,” Proceedings of the IEEE, vol. 102, no. 11, pp. 1723–1746, Nov 2014. [7] B. Cook, C. Mariotti, J. Cooper, D. Revier, B. Tehrani, L. Aluigi, L. Roselli, and M. Tentzeris, “Inkjet-printed, vertically-integrated, highperformance inductors and transformers on flexible LCP substrate,” in Microwave Symposium (IMS), 2014 IEEE MTT-S International, 2014. [8] F. Alimenti, P. Mezzanotte, M. Dionigi, M. Virili, and L. Roselli, “Microwave Circuits in Paper Substrates Exploiting Conductive Adhesive Tapes,” Microwave and Wireless Components Letters, IEEE, vol. 22, no. 12, pp. 660–662, Dec 2012. [9] C. Mariotti, R. Gonalves, L. Roselli, N. Carvalho, and P. Pinho, “”energy evaporation”: the new concept of indoor systems for wpt and eh embedded into the floor,” in IEEE, International Microwave Symposium (IMS), 2015.