Radiofrequency Energy Harvesting System based on a Rectenna Array in the Urban Environment of Brasilia, Brazil EMS Research Group – Fraunhofer IIS and TU Ilmenau Wireless Distribution Systems / Digital Broadcasting LASP – UnB Laboratory of Array Signal Processing Jayme Milanezi Junior, João Paulo C. Lustosa da Costa, Edison Pignaton de Freitas, Giovanni del Galdo, Wolfgang Felber, Ronaldo S. Ferreira Júnior and Ricardo Kerhle Miranda http://www.tu-ilmenau.de/it_dvt/ http://www.redes.unb.br/lasp/ http://www.iis.fraunhofer.de/ Uzbekistan, November 2016 Fachgebiet Hochfrequenz- und Mikrowellentechnik www.tu-ilmenau.de/hmt

Outline DVT Motivation State of the art and candidate solutions Feasability evaluation via measurements Simulation results Conclusions EMT

Outline DVT Motivation State of the art and candidate solutions Feasability evaluation via measurements Simulation results Conclusions EMT

Motivation Energy recycling Increase of the energetic needs versus limited natural sources Exploitation of the produced energy Examples of energy harvesting in the literature: Small piezoelectric generator (shoes movement): 330 μW/cm3 Thermoelectric generator 10 ̊ C gradient: 40 μW/cm3 Acoustic noise generator (100 dB): less than 1 μW/cm3 Radio frequency (RF) energy recycling: transmitted information is not relevant. Signals captured by the antenna are converted into energy. Exploitation of the part of the available hardware Dependence of the ubiquity and intensity of the RF signal in a given location

Motivation RF energy harvesting for Wireless Sensor Networks (WSN) Sensor nodes: low energy consumption of the order of hundreds of mW per unit Changing the batteries of the sensor nodes not feasible in several applications: huge forests and catastrophe areas RF harvesting to extend the life time of the sensors impacting the life time of the whole WSN Multi hop communications Recharging the sensor nodes of the WSN as well as portable electronic devices, such as cell phones Amount of typically harvested power in the order of few microwatts for RF harvesting systems Antenna array based RF harvesting Currently used in 4G wireless communication systems: increased data throughput In case of energy harvesting: Adaptive systems: higher power consumption, lowering the final net power to be harvested

Motivation Antenna array based RF harvesting Contributions Non-adaptive systems: dependence on the direction of arrival of the line-of-sight (LOS) component 5G wireless communications system Massive MIMO systems, where transmitters and receivers are equipped with hundreds of antennas Contributions Proposal of a rectenna array system inspired by antenna array based solutions in telecommunications Feasibility of the RF energy harvesting in real urban scenarios via measurement Measurement performed in Brasília Comparison between rectenna array systems and non-adaptive antenna array based systems for LOS scenarios and for only non-LOS scenarios

Outline DVT Motivation State of the art and candidate solutions Feasability evaluation via measurements Simulation results Conclusions EMT

State of the art and candidate solutions Rectenna for energy harvesting The output of a rectenna is often connected to a battery.

State of the art and candidate solutions Adaptive antenna array systems spend more power.

State of the art and candidate solutions Non-adaptive antenna array systems Overall power depends on the direction of arrival (DOA).

State of the art and candidate solutions Connecting rectennas in series No influence of the DOA of the RF incident waves on the overall power

Outline DVT Motivation State of the art and candidate solutions Feasability evaluation via measurements Simulation results Conclusions EMT

Feasibility evaluation via measurements RF measurements in four different places in Brasília, Brazil Place 3, near TV Tower, provided the best incident power

Feasibility evaluation via measurements A more complete measurement campaign performed in place 3 Higher dBm values than places 1, 2 and 4 Variation of the amount of antennas Antennas fixed onto the roof of the car

Feasibility evaluation via measurements Measurements comprised arrays with 1, 2, 3 and 4 antennas Spectrum analsysis with 4 antennas 93.7 MHz 12.45 dBm (17.59 mW) 91.7 MHz 11.34 dBm (13.61 mW)

Feasibility evaluation via measurements Values of incident dBm according to the amount of employed antennas in place 3

Feasibility evaluation via measurements By performing measurements in specific frequency ranges and with an antenna array with 4 elements an average incidence power: +11 dBm Given the global efficiency of 18 % for RF wave converters, the total power is equivalent to 2.27 mW. In a period of 24 hours, the total harvested energy of 54.48 mWh Given that the consumption of a sensor node consumes is more than 10 mW to transmit a packet over a wireless link, 5 rectennas are needed.

Outline DVT Motivation State of the art and candidate solutions Feasability evaluation via measurements Simulation results Conclusions EMT

Simulation results By means of simulations, we compare the performance of a rectenna array and an antenna array in the presence of multipath components Prec: power produced by a rectenna array Pant: power produced by an antenna array Kt: coefficient for the LOS component varying between 0, 0.3, 0.6 and 1 to represent the presence of shadowing. K: Zero mean Gaussian generated with variance 1. In some generated scenarios: K > Kt

Simulation results Only NLOS scenarios (Kt = 0) and 11 rectennas/antennas: Prec > 2 Pant

Outline DVT Motivation State of the art and candidate solutions Feasability evaluation via measurements Simulation results Conclusions EMT

Conclusions The usage of such amount of energy is mainly applicable to: sensor nodes low power consumption electronic devices For a sensor node consumption of more than 10 mW, 5 rectennas are needed. Less rectennas can be necessary, since only dozens microwatts in sleep mode. Usage of rectenna arrays as well as antenna arrays in buildings close to the TV tower due to the high power electromagnetic waves on the area Antenna arrays without adaptive system: TX and RX are static. Massive antenna systems for 5G mmWave systems (up to 60 GHz) have a high attenuation. Transmitters and receivers in massive MIMO are equipped with hundreds antennas. Such antennas can be exploited in a RF harversting system. Pratical value: approx. 50 antennas to load a cell phone

Thank you for your attention! João Paulo C. L. Da Costa (joaopaulo.dacosta@ene.unb.br) http://www.tu-ilmenau.de/it_dvt/ http://www.redes.unb.br/lasp/ http://www.iis.fraunhofer.de/ Uzbekistan, November 2016 Fachgebiet Hochfrequenz- und Mikrowellentechnik www.tu-ilmenau.de/hmt