Design and Modelling of Wireless Power Transfer and Energy Harvesting Systems

Transcription

1 Design and Modelling of Wireless Power Transfer and Energy Harvesting Systems Marco Fantuzzi, Diego Masotti, and Alessandra Costanzo DEI University of Bologna, Italy UDINE, 22 June 2017

2 Outline Motivations autonomous long distance IoT operations limitations and possible solutions Isotropic RF Energy Harvester isotropic radiation and all-polarization receiver WuR implementation rectenna connections and layout system performance Conclusions and future steps 2

3 Main Requirements Localization of objects for long distance IoT operations combined UWB/UHF UHF Harvesting (intentional WPT) supply µcontroller supply UWB switch WuR addressing synchronization UWB Backscatter modulator localization (European GHz) PMU Main requirements: 500 mv for the cold-start MAX DISTANCE 3

4 Conventional solution dipole-like rectenna single, omnidirectional antenna full-wave rectifier PROS omnidirectional radiation CONS low rectified voltage for high distances polarization dependent (usually CP at TX-side) radation nulls 4

5 Increasing rectified voltage (1/2) single rectenna multi-stage rectifier voltage multiplication UHF antenna Ropt Simulated results: P RF-IN = -20 dbm MN # stages V DC (mv) P DC (µw) RF-dc eff % % % % % no more beneficial 5

6 Increasing rectified voltage (2/2) multiple rectennas Antenna array & single rectifier E inc Multi-antennas & multi-rectifiers E inc RF combiner matching network matching network matching network matching network matching network DC combiner P load RECT exploits the higher gain of the array known direction of arrival P RECT load no array factor unknown direction of arrival 6

7 Increasing rectified voltage (2/2) multiple rectennas: series connection P RF N MN P dc N IDEAL CASE V dc-total N * V dc optimum load N * Ropt V dc-total increased P dc-total increased P RF 2 P RF 1 MN MN P dc 2 P dc 1 V dc-total REAL CASE strong coupling between closely-spaced antennas both V dc and P dc are reduced 7

8 100 mm Proposed solution 4 UHF rectennas 100 mm dip 1 Dual linear polarization: horizontal LP vertical LP right/left CP dip 4 UWB antenna dip 2 Two couples: further Vdc increase full exploitation of tag area and UWB antenna co-location dip 3 8

9 100 mm Optimized distance 100 mm dip 1 GOAL: overall gain maximization dip 4 D UWB antenna dip Gain (dbi) 0 q D λ/2.5 λ/3.5 λ/4.5 λ/5.5 dip 3 y z θ φ x 180 dip 1 φ = 90 9

10 Radiation patterns Optimized gain 2.1 dbi in z-direction 1.7 dbi in lateral direction RF power received from all directions dip 1 minor influence on UWB antenna (gain from 3 to 6 dbi in the UWB band) 10

11 WuR activation Wake-up radio Voltage splitting in dc: lossy resistive divider ultra-low power MCU in sleeping mode, turn-on when interrogated Voltage splitting at RF: capacitive divider no loss MN C UP C DOWN V Rect V WuR TX is CP: voltage division only in first rectenna WuR turn-on voltage: 60 mv 11

12 Layout and prototype dc outputs V rect GND V WuR Rogers RO4350B (thick. 1.5 mm, ε r = 3.48, tan(δ) = ) stage mm stage 4 stage 2 stage mm 36 mm 12

13 Layout and series connection V rect GND V WuR Z ant4 L 4 dc block V rect stage mm #4 C 4A C 4B C rect Z ant3 L 3 dc block 100 mm stage 4 stage 2 #3 C 3A C 3B C rect 36 mm #2 Z ant2 L 2 dc block stage 3 C 2A C 2B C rect Z ant1 L 1 dc block Part name diodes Value Skyworks SMS-7630 (SC-79) #1 C 1A C 1B C UP C rect dcblock Murata 10 pf dc block V WuR CUP Murata 0.9 pf CDOWN Murata 1.7 pf C DOWN C WuR Crect Murata 10 pf CWuR Murata 10 pf 13

14 Pdc (µw) RF-dc efficiency (%) Experimental validation OC Voltage TX: 2 W ERP P dc - EFF Vdc (mv) RECT_sim RECT_meas WuR_sim WuR_meas single dip. -20 Available RF input power (dbm) 42% improvement with respect to single dipole rectenna SIM MEAS distance from TX (m) Vdc = 500 mv Pdc = 7.6 µw activation at 12.6 m 14

15 Conclusions and future steps quasi-isotropic energy harvester real applications scenarios: unknown position of the RF sources all-polarization receiving capabilites real applications scenarios: unknown polarization of RF sources increased activation distance with a maximum activation distance of 12.6 m most of the typical indoor scenarios can be covered 15

16 Conclusions and future steps Further steps two-rectennas for WuR: all-pol receiving and voltage multiplication shielding to background materials: low-profiles solutions, e.g. metamaterials multi-source dc/dc converter: each rectenna has its R opt higher total dc power 16

17 Thank you Marco Fantuzzi University of Bologna 17