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1 IEEE PEDS 017, Honolulu, USA 1 15 Decembe 017 Enhancing Wiele Powe Tanfe Capability of Inductive Powe Tanfe Sytem Uing Matix Powe Repeate Rong Hua*, Student membe, IEEE, Bo ong, Aiguo Patick Hu, Senio membe, IEEE Depatment of Electical and Compute Engineeing The Univeity of Auckland New Zealand hua07@aucklanduni.ac.nz* Abtact Matix powe epeate (MPR) with multiple unit cell have been uccefully ued in fa field adio ytem fo concentating electomagnetic wave. Howeve, thei effect on the field ditibution in non-adiative nea field wiele powe tanfe ytem ae not well undetood. Thi pape i to popoe a new method fo enhancing the wiele powe tanfe capability of Inductive powe tanfe (IPT) ytem uing MPR. A ytem model i etablihed by conideing the contibution of each individual unit cell of a typical MPR, which i ued to analyze the powe tanfe pefomance of an IPT ytem. A citical condition in elation to the mutual inductance between the pimay/ econday coil and MPR individual coil i detemined, which define the bounday between enhancing and educing the powe tanfe of an IPT ytem. A pactical MPR i built and teted to meet the powe tanfe enhancement condition, and expeimental eult how that the output powe of an IPT ytem i inceaed by 34.4%. Keywod Inductive Powe Tanfe, Matix powe epeate I. INTRODUCTION Inductive powe tanfe (IPT) i a popula wiele powe tanfe technology baed on magnetic field coupling. The concept ha been moe than 100 yea old ince it wa fitly popoed by Tela [1], but it wa only until ecently IPT ha gained ucceful application in conume electonic [-4], medical implant [5-8] and building monitoing [9]. One containt of an IPT ytem i it powe tanfe capability decay quickly with the inceae of powe tanfe ditance. age coil have been ued to impove the magnetic field coupling and theeby the powe tanfe capability [10], and advanced compenation and contol technique have been developed to inceae the powe tanfe capability of looely coupled IPT ytem [11]. Howeve, pactically the coil ize ae often limited by the phyical containt of a ytem, and due to the natue of magnetic field coupling, the powe tanfe capability i limited by the path of a magnetic cicuit, which cannot be enhanced by jut extenal cicuit compenation and contol. Matix powe epeate, which ae alo named a metamateial, have the ability of concentating fa field electomagnetic wave. Howeve, it i not clea whethe they can be ued in nea field IPT ytem fo enhancing the powe tanfe capability. High fequency matix powe epeate have been ued fo electomagnetic cloaking [1], pefect len deign [13], and deign of adio antenna [14]. In mot of thee application, matix powe epeate ae opeated with a fequency ange fom a few hunded MHz to a few GHz. By contat, the ytem opeating fequency of a non-adiative nea field wiele powe tanfe ytem i nomally within a few ten o hunded of khz. Thee i a need fo tudying the effect of MPR on nea field wiele powe tanfe ytem. Thi pape i to popoe a new method fo enhancing the powe tanfe capability of an IPT ytem by placing a matix powe epeate in the middle between pimay and econday coil. II. PROPOSED SYSTEM MODE AND SYSTEM ANAYSIS Fig.1 illutate an IPT ytem with a typical matix powe epeate. The MPR i placed in the middle between a pimay tanmitte and a powe pickup, and the pimay tanmitting coil, the MPR and the powe pickup coil ae coaxial aligned. The pimay tanmitting coil and the powe pickup coil have a ame diamete which equal to the length of the MPR edge. The coil of unit cell and the powe pickup coil ae nominal tuned to the ytem opeating fequency. Fig. how a typical matix powe epeate. The MPR include 9 identical unit cell, and it dimenion i 130mm 130mm 1.77mm. Unit cell ae chaacteized into cente, edge and cone type baed on thei location in the MPR. Each unit cell contain a plana quae pial coil with 14 tun on both ide of the MPR. The plana coil on diffeent ide of the MPR ae connected in eie, and they ae tuned to fequency of inteeting uing a eie connected capacito. H 0 0 Fig.1 An IPT ytem with a typical MPR placed in the middle between a pimay coil and powe pickup coil H /17/$ IEEE 957

2 1 1 ω = = (1) MPR C whee ω i the ytem angula fequency, i the inductance of the pickup coil, C i the tuning capacitance of the pickup coil. By uing Kichhoff voltage law (KV) in eonant cicuit of a unit cell of each type and the powe pickup, ()i deived. Fig. A typical matix powe epeate with 9 identical unit cell Fig. 3 how the ytem model. The pimay tanmitting coil i modelled a an inducto p. The MPR i modelled a 9 CR eonant cicuit with ame inducto MPR, Equivalent Seie Reitance (ESR), and capacito C MPR. The mutual inductance between the pimay tanmitting coil and coil of ame type of unit cell ae aumed to be ame becaue the ditance between thei cente ae equal. The mutual inductance between the pimay tanmitting coil and coil of cente, edge and cone type of unit cell ae modelled a M 1, M and M 3, epectively. The powe pickup i modelled a CR cicuit with a load eitance R.. A the MPR i in the middle between pimay coil and pickup coil, mutual inductance between the powe pickup coil and the coil of cente, edge and cone type of unit cell ae alo modelled a M 1, M and M 3, epectively. The mutual inductance between the pimay tanmitting coil and the pickup coil i modelled a M p. p Pimay tanmitte M3 M1 M MPR MPR 3 MPR M1 MPR M M3 C R Powe pickup jωm1ip + ZMPRI1 + jωm1i jωmip + ZMPRI + jωmi jωm I + Z I + jωm I 3 p MPR 3 3 jωm I + jωm I + 4jωM I + 4jωM I + Z I PS p whee I 1, I, and I 3 i the cuent in coil of cente, edge and cone type of unit cell, epectively, I p i contant cuent goe though the pimay coil, I i the cuent in the pickup coil, Z MPR and Z S i the impedance of a unit cell and the powe pickup, epectively, and they can be epeented a 1 ZMPR = jωmpr + + jω 1 Z = jω R jωc whee i the ESR of the pickup coil By ubtituting (1) into(3), and (3)into(), () i implified a: jωm1i p + I1 + jωm1i jωm I p + I + jωm I jωm I + I + jωm I 3 p 3 3 jωm I + jωm I + 4jωM I + 4 jωm I + ( + R ) I PS p By imultaneouly olving 4 equation in (4), the output cuent i obtained a : I ω ( M + 4M + 4 M ) + jωm p = ( ) I ω ( M + 4M + 4 M ) + ( + R ) The amplitude of the pickup cuent i epeented a: p () (3) (4) (5) 3 MPS I 4 ω ( M1 + 4M + 4 M3) + ω Mp = ( ) I ω ( M + 4M + 4 M ) + ( + R ) 1 3 p (6) Fig. 3 The popoed ytem cicuit model A all unit cell and the powe pickup ae nominal tuned, theefoe, The ytem output powe can be calculated uing (7). out P = I R (7) 958

3 Fig. 4 The imulation et up of an IPT ytem with a MPR in TSPICE By ubtituting (6) into(7), the output powe i obtained a: ω ( M + 4M + 4 M ) + ω M P I R p out = p ( ω ( M1 + 4M + 4 M3) + ( + R)) To find the condition fo enhancing the powe tanfe capability, the output powe of the ytem without the MPR i obtained uing(9) [15]. Voc Pout1 = ( ) R R + whee Voc i the open cicuit voltage of the pickup coil of the ytem without the MPR, and it can be epeented a oc p p (8) (9) V = jωm I (10) By ubtituting (10) into(9), the output powe i obtained a: M pωip Pout1 = ( ) R R + (11) The citical condition i found by etting (8) to be lage than(11), and olving the equation. The citical condition i detemined a: whee M p ( R + ) + pc A > ( R ) M ω A= ( M + 4M + 4 M ) 1 3 (1) Equation (1) epeent the condition of the 9 unit cell MPR fo enhancing the powe the powe tanfe of an IPT ytem when the powe epeate i placed in the middle of the pimay and econday coil. If the mutual inductance M 1, M and M 3 ae ufficiently lage to make paamete A meet the condition defined by(1), moe powe will be tanfeed to the powe pickup. III. SIMUATION STUDY Simulation ae conducted uing imulation oftwae package TSPICE. Fig. 4 how imulation etup of an IPT ytem without MPR. The pimay tanmitte i et to be a contant cuent ouce connected with a eie CR eonant cicuit. The MPR i et to be 9 CR eonant cicuit with ame inductance, capacitance and ESR. A CR eie eonant cicuit connected with a eitance i et to be the pickup cicuit. The cicuit paamete ued in the imulation ae baed on pactical meauement, and they ae hown in TABE I µh TABE I CIRCUIT PARAMETERS USED IN THE SIMUATION Component Value f I p(rms) 105 khz A p p mω C 13.7 µh 173.nF mω MPR C MPR µh 150nF MPR 1.503Ω R 5.68 Ω M µh M µh M µh M p.3 µh 959

4 By ubtituting the paamete into(1), the citical condition fo enhancing the powe tanfe i met. Fig.5 (a) and (b) how the voltage aco the load eitance with and without the MPR, epectively. (a) Fig. 6 The expeimental etup (b) Fig.5 The output voltage of the ytem (a) with the MPR, (b) without the MPR Fom Fig.5 (a), the peak output voltage i 4.7 V, and the output powe i calculated to be W. Fig.5 (b) how that the peak voltage i 4.08 V, and the output powe i calculated to be W. The output powe i inceaed by 33.9% by uing the MPR. IV. EXPERIMENTA RESUTS Fig. 6 how the expeimental etup. It include a linea amplifie, a pimay coil, a MPR, a powe pickup coil and a pickup cicuit. The powe pickup coil wa placed 50mm away fom the pimay coil, and both pimay coil and powe pickup coil wee made uing telephone cable with 10 tun, inte adiu of 31.5mm and oute adiu of 60mm. The pimay coil, the MPR and powe pickup coil wee coaxial aligned, and the MPR wa placed in the middle between the pimay coil and the powe pickup coil. Fig.7 how a pactical MPR. Plana quae coil wee pinted on both ide of a FR4 plate, and plana coil on diffeent ide of the FR4 plate wee eie connected uing jump wie. The eie connected plana coil wee tuned at 105 khz uing 150 nf capacito with eie connection. The ytem paamete ued in the expeiment ae ame a paamete ued in the imulation tudy, which ae hown in TABE I. Fig.7 The pactical Matix Powe Repeate In the expeiment, the input cuent in the pimacy coil wa et to be aound A by manually contolling the input voltage of the amplifie. The voltage aco the load eitance wa meaued fitly without putting the MPR in the ytem. Then, the MPR wa placed in the ytem, and the voltage aco the load eitance wa meaued again. Fig. 8 (a) and (b) how the meaued pimay cuent and output voltage of the ytem with and without the MPR, epectively. (a) 960

5 (b) Fig. 8 The meaued pimay cuent (yellow cuve) and output voltage (geen cuve) of the ytem (a) without the MPR, (b) with the MPR Fig. 8(a) and (b) how that input pimay cuent i cloe to A fo the ytem with and without the MPR. Fig. 8 (a) how the RMS value of the output voltage i.85v, and the output powe i calculated to be W. The RMS value of the output voltage i 3.75 V in Fig. 8 (b), and the output powe i calculated to be W. The output powe i inceaed W by uing the MPR. V. CONCUSION Thi pape ha popoed a new method to enhance the powe tanfe capability of IPT ytem by uing a matix powe epeate. A ytem model ha been popoed by conideing the contibution of each individual unit cell of a typical MPR. A citical condition in elation to the mutual inductance between the MPR and the pimay/econday coil fo enhancing the powe tanfe of IPT ytem ha been defined. Expeimental eult baed on a pototype of IPT ytem with a MRP placed in middle have hown that the output powe ha been inceaed fom W to W when the citical condition i met. [6] P. Si, A. P. Hu, S. Malpa, and D. Budgett, "A Fequency Contol Method fo Regulating Wiele Powe to Implantable Device," IEEE Tanaction on Biomedical Cicuit and Sytem, vol., pp. -9, 008. [7] D. McComick, A. P. Hu, P. Nielen, S. Malpa, and D. Budgett, "Poweing implantable telemety device fom localized magnetic field," in 007 9th Annual Intenational Confeence of the IEEE Engineeing in Medicine and Biology Society, 007, pp [8] P. Si, A. P. Hu, D. Budgett, S. Malpa, J. Yang, and J. Gao, "Stabilizing the opeating fequency of a eonant convete fo wiele powe tanfe to implantable biomedical eno," in Poc. 1t Int. Conf. Sening Technology, 005, pp [9] M. Sala, O. Focke, A. S. Hemann, and W. ang, "Wiele Powe Tanmiion fo Stuctual Health Monitoing of Fibe- Reinfoced-Compoite Mateial," IEEE Seno Jounal, vol. 14, pp , 014. [10] A. Ku, A. Kaali, R. Moffatt, J. D. Joannopoulo, P. Fihe, and M. Soljačić, "Wiele powe tanfe via tongly coupled magnetic eonance," cience, vol. 317, pp , 007. [11] B. Wang, A. P. Hu, and D. Budgett, "Powe flow contol baed olely on low feedback loop fo heat pump application," Biomedical Cicuit and Sytem, IEEE Tanaction on, vol. 6, pp , 01. [1] D. Schuig, J. Mock, B. Jutice, S. A. Cumme, J. B. Pendy, A. Sta, et al., "Metamateial electomagnetic cloak at micowave fequencie," Science, vol. 314, pp , 006. [13] J. B. Pendy, "Negative efaction make a pefect len," Phyical eview lette, vol. 85, p. 3966, 000. [14]. iang-yuan and W. Bing-Zhong, "A Boadband and Electically Small Plana Monopole Employing Metamateial Tanmiion ine," Antenna and Wiele Popagation ette, IEEE, vol. 14, pp , 015. [15] A. P. Hu, "Selected eonant convete fo IPT powe upplie," ReeachSpace@ Auckland, 001. REFERENCES [1] H. W. Seco, "Tela appaatu and expeiment How to build both lage and mall Tela and Oudin coil and how to cay on pectacula expeiment with them," Pactical Electic, Nov, 191. [] J. Kim, H.-C. Son, D.-H. Kim, and Y.-J. Pak, "Optimal deign of a wiele powe tanfe ytem with multiple elf-eonato fo an ED TV," Conume Electonic, IEEE Tanaction on, vol. 58, pp , 01. [3] J. Baek, C. Ahn, B.-c. Kim, S. Choi, and S. Kwak, "High fequency wiele powe tanfe ytem fo obot vacuum cleane," in Conume Electonic (ICCE), 014 IEEE Intenational Confeence on, 014, pp [4] R. Tevian and A. Cotanzo, "Exploitation of paive RFID technology fo wiele ead-out of tempeatue eno," in RFID Technology and Application Confeence (RFID-TA), 014 IEEE, 014, pp [5] D. M. Budgett, A. P. Hu, P. Si, W. T. Palla, M. G. Donnelly, J. W. Boad, et al., "Novel technology fo the poviion of powe to implantable phyiological device," Jounal of Applied Phyiology, vol. 10, pp ,