Research Article Integration of Resonant Coil for Wireless ...downloads.hindawi.com/journals/ijap/2016/7101207.pdf · the biomedical implant devices, such as capsule endoscope, pacemaker,

Research ArticleIntegration of Resonant Coil for Wireless Power Transfer andImplantable Antenna for Signal Transfer

Dong-Wook Seo Jae-Ho Lee and Hyungsoo Lee

Automotive IT Platform Research Section Electronics and Telecommunications Research Institute (ETRI) 1 Techno Sunhwan-ro 10-gilYuga-myeon Dalseong-gun Daegu 42994 Republic of Korea

Correspondence should be addressed to Jae-Ho Lee jhlee1229etrirekr

Received 12 April 2016 Accepted 26 May 2016

Academic Editor Sanghoek Kim

Copyright copy 2016 Dong-Wook Seo et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

We propose the integration of the resonant coil for wireless power transfer (WPT) and the implantable antenna for physiologicalsignal transfer The integration allows for a compact biomedical implantable system such as electrocardiogram (ECG) recorderand pacemaker While the resonant coils resonate at the frequency of 1356MHz for the WPT the implantable antenna works inthe medical implant communications service (MICS) band of 402ndash405MHz for wireless communications They share the narrowsubstrate area of a bar-type shape the coil has the current path on the outer part of the substrate and themeandered planar inverted-F antenna (PIFA) occupies the inside of the coil To verify the potentials of the proposed structure a prototype is fabricated andtested in vitro The power transfer efficiency (PTE) of about 20 is obtained at a distance of 15mm and the antenna gain of roughlyminus40 dBi is achieved

1 Introduction

Recently with growing interests in U-healthcare studies onthe biomedical implant devices such as capsule endoscopepacemaker electrocardiogram (ECG) recorder neurostim-ulator and retinal implant have drawn high attention Forwireless communications with implanted units the med-ical implant communication service (MICS) band (402ndash405MHz) is recommended by the Federal Communica-tions Commission (FCC) An implantable antenna works inhuman or animal body and ensures the wireless commu-nications and many researches on the implantable antennadesign have also been carried out [1ndash9] Unlike typical anten-nas used in the air the implantable antenna should satisfyvarious requirements and constraints such as antenna shapebiocompatibility miniaturization and broad bandwidthTheshape and biocompatibility are mainly determined by theimplant part of the body and a package material respectively[10] The well-known antenna minimization technique is touse the high-permittivity substrates (eg Rogers 30103210with 120576

119903= 102) which shorten the effectivewavelength In the

structural aspect the dipole with spiral arms [1] meanderedplanar inverted-F antenna (PIFA) [3] and spiral PIFA [4] has

been designed for this purpose Additionally the extendedcurrent path using slots or notches on the radiating patch[5] and the open-end slot antenna with a meandered slot onthe top metal [6] are also suggested Stacked structure is alsointroduced to reduce the antenna area even if the pitch ofantenna is higher [7ndash9]

On the other hand the electric components of animplant device need a power source Conventional biomed-ical implant devices have been supplied with electric powerby an internal primary cell which should be unfortunatelyreplaced through a surgery with a discharge cycle The wire-less power transfer (WPT) has been considered a noticeablealternative [11] and has been studied to recharge an internalsecondary cell Recently studies on theWPT have focused ontransmitting not only several mW for small devices but alsoseveral kW for electric vehicles Moreover various methodsto improve the power transfer efficiency (PTE) have also beenresearched [12ndash14]

Early studies related to the implant device have used aninductive link to simultaneously implement wireless com-munication and wireless power transfer In this case thehigh 119876-factor of resonant coils to achieve the high PTEbrings about narrowing the communication bandwidth the

Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2016 Article ID 7101207 7 pageshttpdxdoiorg10115520167101207

2 International Journal of Antennas and Propagation

ECG sensor

Base-stationBluetooth

Personal terminal

MICS bandcommunications

WPT using ISM band

Figure 1 The concept developing the ECG monitoring system

Epidermis

Dermis

Fat

Muscle

Magnetic field

Outside body

MICS ant

MICS ant

Rx resonantcoil

Tx resonantcoil

EM field

2mmndash3 cm

11ndash3mm

003ndash013mm

Figure 2 Inductive and electromagnetic links between the implantdevice and base-station

tradeoff exists between the PTE and data rate In order toovercome these disadvantages the power allocation strategyusing an orthogonal frequency-division multiplexing systemis suggested [15] However in most recent researches theWPT system operates at the industrial scientific medical(ISM) band such as 678MHz and 1356MHz to easilyimplement a resonant coil with high 119876-factor and usesthe outband communications to achieve the high datarate

Our group has developed an ECG monitoring system asshown in Figure 1 An implant device communicates with abase-station using the MICS frequency band and transfersthe sensed ECG signals to the exterior base-station Con-secutively the collected ECG signals can be sent wirelesslyto a personal terminal via Bluetooth On the other handthe power is wirelessly transferred from the base-station tothe implant device at 1356MHz That is the base-stationof the ECG monitoring system transfers simultaneously thepower and signal into the implantable medical device usingthe outband communications

Because the ECG signals are detected in the skin layerthe implant device is usually inserted in the subcutaneous fatlayer for the ECG monitoring system as shown in Figure 2and then the implant depth is about 3mm to 20mm Inour design concept the implant device should have a bar-type shape in order to minimize the skin incision part andthe height of the implant board should be low to minimizethe foreign body sensation of skin In the MICS bandthe transmit power has to be less than 25120583W (minus16 dBm)and the MICS antenna should have the gain greater than

minus45 dBi from the link budge analysis to achieve theminimumcommunication distance of 2m On the other hand thegap between two electrodes of the ECG sensor should belarger than 30mm in order to capture the stable ECG signalTherefore the implant coil size is set to 30mm times 5mmwhile there is no size limit for the external coil Since thepower is transferred from the external coil to the implantcoil only when the secondary battery needs charging theexternal coil connected with the base-station is put on theskin or clothes only under chargingTherefore themaximumdistance between two coils is about 20mm In additionbecause the implant device receives the signal and powersource from the exterior base-station the resonant coil andMICS antenna should be located on the outward surface ofthe implant device

In [16] the Rx resonator operating at 678MHz integratedwith an antenna for theMICS band is proposed Inserting theferrite material below the coil generates the antenna currentpath However the height of integrated resonator and MICSantenna is not low due to the ferrite material

In this study integration of the coil and antenna on a com-mon substrate is proposed for the implant device with lowprofile Particularly unlike most of the MICS antennas usingsubstrate with high permittivity the multilayer substrate ofthe ferrite sheet and FR-4 is utilized for significant size-reductionTheir potentials for the applications are verified bysimulations and experiments

In the following we first present the proposed integrationgeometry of the resonant coil and MICS antenna We thengive details about design of integrated resonant coil withMICS antenna And then we describe the development oftissue-emulating materials that are used for in vitro mea-surements Finally we present simulation and measurementresults

2 Geometry of Resonant Coil andMICS Antenna

Figure 3 shows the configuration of the proposed integrationof the Rx resonant coil and MICS antenna for the ECGmonitoring system The integration pattern module has asize of 225mm3 (30mm times 5mm times 15mm) A conductingmeandered PIFA and upper coil pattern are printed on a08mm thick FR-4 substrate (120576

119903= 44 tan 120575 = 0013) and

the lower coil pattern is printed on the bottom of the FR-4substrate To isolate the implant device from the conductivetissue the quartz superstrate (120576

119903= 378) packages the implant

device The ferrite sheet is inserted between the FR-4 and theground plane to shorten the effective wavelength and shieldmagnetic field interfering with the other circuits

As it can be observed from Figure 3(b) the prototype ofthe implant device consists of the bottom circuit module andtop integration pattern module The circuit module includestheMICS transceiver ECG sensor part impedance matchingnetwork and charge circuit The integration pattern moduleis the resonant coil integrated with the MICS antenna ofFigure 3(a) The connection between the two modules isrealized and fixed with a low-profile connector

International Journal of Antennas and Propagation 3

Rx coil Rx antenna

FR4

Ferrite sheetGround

30mm

5mm

(a)

Integration pattern module of coil and antenna

Circuit modulefor wireless communication and WPT

3mm

5mm

30mm

(b)

Figure 3 The proposed resonant coil and MICS antenna (a)perspective view and (b) fabricated prototype of the implant device

3 Integration of MICS Antenna withResonant Coil

The integration pattern module has a narrow bar-type shapefor easy injection with a guider such as the hypodermicsyringe The integration size is determined to be 30mm times

5mm which is the same dimension as that of the bottomcircuit module

31 Design Process Since the MICS antenna is located on theinner area of the Rx resonant coil the MICS antenna andthe resonant coil inevitably affect each other Therefore anintegration design process is required in consideration of themutual influence between the two elements and it is illus-trated on a flow chart shown in Figure 4 Once the implantdepth is selected system requirements can be translated intoantenna requirements through a link budget analysis and thecoil size is determined by themaximumcircuit board size andimplant part of a human bodyThese requirements determinethe materials for coil and antenna construction In this studythe FR-4 and ferrite sheet are selected as substrates and thequartz is selected as a superstrate In the next step the linewidth the gap between the lines and the number of turns andlayers are designed Coil parametric study and optimizationare performed until the119876-factor is maximized in simulation

A MICS antenna is first modeled simulated and opti-mized by finely adjusting the antenna size gain andmatchingpoint In the next step the unloaded119876-factor of the resonantcoil is recalculated and is compared with the desired valueIf the resonant coil fails to satisfy the desired 119876-factor theresonant coil andMICS antenna are redesigned until require-ments are met In the last step of the design process thecapacitance is calculated to make the resonant coil resonateat the operating frequency using the designed inductance

32 Design of Rx Resonant Coil The goal of coil designis to obtain the maximized unloaded 119876-factor It is widelyknown that the unloaded119876-factor of a coil has a tendency to

Start

Design the Rx coil

Select substrate and superstrate

Design the Rx antenna

factor

End

Estimate the capacitance forresonance

YesNo

Desired Q-

Calculate the unloaded-Q of coil

Figure 4 Design process of the integration of the resonant coil andMICS antenna

30mm

5m

mlguard

lwidth Rxlgap Rx

l1

l2l3l4

(a)Quartz

FR-4

Ferrite sheet Ground

Upper layerLower layerVia hole pattern pattern

hquartzhsubhferrite

(b)

Figure 5 Geometry of the designed Rx resonant coil (a) top and(b) side

increase with the large inner area wide line width and longline length of the coil However if the line length exceeds acertain level the ohmic loss becomes dominant rather thanthe inductance and consequently the 119876-factor of the coildecreases Therefore the design of Rx resonant coil will becompleted after several iterations

As shown in Figure 5 the Rx resonant coil has two-layer and four-turn structure The coil patterns are printedon 08mm thick (ℎsub) FR-4 substrate and 05mm thick(ℎquartz) quartz superstrate covers the structures to preventit from directly contacting the lossy tissue 02mm thick(ℎferrite) ferrite sheet is used to reduce the ground effect andto prevent magnetic flux from interfering with the bottomcircuit module

It requires that the coil has the large inner area to securean antenna region and to achieve the high119876-factorThus theline width (119897widthRx) and the gap (119897gapRx) between the lineshave minimum values 015mm and 013mm respectively


lshortlfeed

lw ant

l1l1l2 l3

Want

(a)

Quartz

FR-4


Lower layerVia hole

Antenna patternUpper layer coil pattern

Shorting pin

Feeding pin

coil pattern

(b)

30mm

5m

m

(c)Figure 6 Geometry of the proposed resonant coil and MICSantenna (a) top (b) side and (c) bottom

Theprinted patterns are 03mm (119897guard) apart from the edge ofprinted circuit board (PCB) The number of turns and layersis optimized using the high frequency structural simulator(HFSS) of Ansys

33 Design of MICS Antenna In our structure the MICSantenna occupies the inner area of resonant coil about 3mmtimes 28mm To reduce the antenna size the meandered PIFAstructure is adopted as shown in Figure 6 The resonantfrequency is determined by the meandering path length andshorting pin position and the antenna input impedance iscontrolled by the position of feeding pin The antenna width(119882ant) is set to be 28mm and the line width (119897

119908ant) ischosen to be 03mm The parameters (119897

1 1198972 and 119897

3) related

to the meandered line are finally determined to be 05mm2525mm and 17mmfor the antennarsquos resonance in theMICSbandTheparameters (119897feed and 119897short) relevant to the positionsof feeding pin and shoring pin are 165mm and 05mmrespectively

In comparison with usual substrates used for theimplantable antenna the FR-4 has relatively low permittivity120576

119903= 44 while the ferrite sheet for shielding magnetic field

by the coils has high permeability its relative permeabilityis 131 at 1356MHz and 31 at 400MHz Therefore the ferritesheet with high permeability allows reducing the effectivewavelength on the PCB As a result the meandered PIFAcan be effectively minimized Due to bottom ground planein addition the antenna gain increases and the back lobedecreases

4 Design of Tx Resonant Coil

Consider two coaxial circular coils with radii 119903Rx and 119903Txrespectively For the two paralleled coils separated by distance119889 the mutual inductance is given by [17]

119872 = 120583

0radic119903Rx119903Tx [(

2

119896

minus 119896)119870 (119896) minus

2

119896

119864 (119896)] (1)

d

30mm

5mm

lguardlwidth Tx

lgap Tx

WTxDTx

Figure 7 Geometry and comparison of the designed Tx coil and Rxcoil

where119870(119896) and 119864(119896) are the complete elliptic integrals of thefirst and second kind respectively and

119896

2

=

4119903Rx119903Tx

(119903Rx + 119903Tx)2

+ 119889

2

(2)

Maximummutual inductance results in maximizing cou-pling coefficient in which the PTE becomes also maximizedTherefore the maximum PTE can be achieved by usingthe condition of maximum mutual inductance in a givenenvironment Equation (1) is the monotonically increasingfunction of 119896 Assume that the radius of Rx coil is a constant 119886times the radius of Tx coil (ie 119903Rx = 119886times 119903Tx) then we obtainthe maximum value of 119896 by differentiating (2) as follows

120597119896

120597119886

= 0 997904rArr 119903Tx = radic

119903

2

Rx + 1198892

(3)

Therefore the radius of the Tx coil size having maximummutual inductance is determined when we know the radiusof the Rx coil 119903Rx and the distance between the coils 119889

In our case the derived equation of (3) cannot be utilizedstraightforwardly due to the Rx coil of the bar-type shapebut it helps to establish a guideline of the Tx coil size Thedistance between the coils is 15mm and the length from thecenter of Rx coil to its sides is set to 119903Rx of (3) Thereforethe estimated length (119863Tx) and width (119882Tx) of Tx coil are424mmand 304mm respectivelyTheparameters of Tx coilare also optimized and then the Tx coil has single layer andfour turns as shown in Figure 7The line width (119897widthTx) andthe gap (119897gapTx) are 035mm and 06mm respectively

5 Simulation and Experiment

51 Fabrication of Tissue-Emulating Materials To verify thepotentials of the proposed structure a prototype is testedin vitro using a tissue-emulating material which is made ofdeionized water saccharose sodium chloride agarose andTX-150 (known as ldquosuper stuffrdquo) The recipes of the tissue-emulating material equivalent to dry skin for 1356MHz and402MHz are presented in Table 1


Table 1 Recipe of human dry skin tissue-emulating material for 1356MHz and 400MHz

Freq MHz AgarTX-150ww

Sodium Chlorideww Sacharose ww Aluminum

powder ww H2O ww

1356 98 (TX-150) 03 mdash 92 807400 10 (Agar) 28 522 mdash 450

Agilent E4991A

Agilent 85070E

Samples

Agilent 85070

E4991A option 010

Figure 8 Measurement setup for tissue-emulating materials

Figure 8 shows the measurement setup for tissue-emulating materials We measured the permittivity in therange of 10MHz to 500MHz by using Agilentrsquos E4991Aimpedance analyzer and Agilentrsquos 85070E high temperatureprobe

Figure 9 shows the measured relative permittivity andconductivity of the gel for 1356MHz and 402MHz the valuesof which are 2825 and 024 Sm at 1356MHz and 432 and0704 Sm at 402MHzThese measured values are within theerror of 10 in comparison with the desired values (120576

119903=

28525 and 120590 = 0238 Sm at 1356MHz and 120576

119903= 467 and

120590 = 0704 Sm at 402MHz for human skin)

52 Simulation and Experiment Results The simulated andmeasured reflection coefficient frequency responses of themeandered PIFA antenna in the skin tissue model arepresented in Figure 10(a) The measured frequency band isranging from 325MHz to 502MHz with a minus10 dB bandwidthcriterion (from 350MHz to 420MHz in the simulation withthe same criterion)

Figure 10(b) depicts the simulated gain radiation patternsin the 119909119911- and 119910119911-planes at 402MHz The maximum gainof minus403 dBi is expected whose value satisfies the antennarequirement as mentioned in Introduction

At the resonant frequency of 1356MHz the simulatedand measured Rx coil parameters are presented in Table 2Good agreement exists between the measured and simulatedresults When the distance between the coils is 15mm thePTE is achieved about 20

6 Conclusion

In this paper the integration of the resonant coil andMICS antenna with narrow bar-type shape is investigatedTo design the compact integration module the multilayer

Rela

tive p

erm

ittiv

ity (120576

r)

Measured 120576rDesired 120576r

Measured 120590

Desired 120590

00

05

10

15

20

Con

duct

ivity

(Sm

)

0

100

200

300

400

500

15 20 25 30 35 40 45 5010Frequency (MHz)

(a)

Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

30

35

40

45

50

55

60

00

05

10

15

20

Con

duct

ivity

(Sm

)

350 400 450 500300Frequency (MHz)

(b)

Figure 9 Measured permittivity and conductivity of the developedtissue-emulating materials (a) for 1356MHz and (b) for 402MHz

Table 2 Rx coil parameters and power transfer efficiency

Rx coil Simulation Experiment

119871 nH 5952 6056119877Ω 259 21119876 196 2457119896 0034 0035120578 19 21


MeasuredSimulated

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Refle

ctio

n co

eff (

dB)

250 300 350 400 450 500 550 600200Frequency (MHz)

(a)

030

60

90

120

150180

210

240

270

300

330

xz-plane (120601 = 0∘)

yz-plane (120601 = 90∘)

minus40

minus45

minus50

minus55

minus50

minus45

minus40

(b)

Figure 10 Performance of the designed MICS antenna (a) simu-lated andmeasured reflection coefficient frequency response and (b)simulated far-field gain radiation patterns

substrate of ferrite sheet and FR-4 is used instead of ahigh-permittivity substrate On the common substrate theresonant coil encloses the meandered PIFA The proposednarrow bar-type structure can be suitable for the biomedicalimplant devices such as ECG recorder and pacemaker whichare inserted into the subcutaneous tissue

The potentials of the designed resonant coil and MICSantenna for implant device were completely demonstratedthrough fabrication of a prototype and measurement withtissue-emulating materials In measurement the MICSantenna had the frequency band ranging from 325MHzto 502MHz with a minus10 dB bandwidth The measured PTEbetween the designed Rx and Tx coils was 21 at a distanceof 15mm

Competing Interests

The authors declare that they have no competing interests

Acknowledgments

This work was supported by ETRI RampD Program [16ZC3300Advanced Development of Fusion-Platform and Local PartsMaker Support Project for Context-Aware Smart Vehicle]funded by the Government of Korea

References

[1] J-H Lee D-W Seo and H S Lee ldquoDesign of implantablerectangular spiral antenna for wireless biotelemetry in MICSbandrdquo ETRI Journal vol 37 no 2 pp 204ndash211 2015

[2] A Kiourti and K S Nikita ldquoA review of implantable patchantennas for biomedical telemetry challenges and solutionsrdquoIEEE Antennas and Propagation Magazine vol 54 no 3 pp210ndash228 2012

[3] T Karacolak A Z Hood and E Topsakal ldquoDesign of a dual-band implantable antenna and development of skin mimickinggels for continuous glucose monitoringrdquo IEEE Transactions onMicrowave Theory and Techniques vol 56 no 4 pp 1001ndash10082008

[4] J Kim and Y Rahmat-Samii ldquoImplanted antennas inside ahuman body simulations designs and characterizationsrdquo IEEETransactions on Microwave Theory and Techniques vol 52 no8 pp 1934ndash1943 2004

[5] K S Nikita J C Lin D I Fotiadis and M T ArredondoldquoEditorial Special issue onmobile and wireless technologies forhealthcare deliveryrdquo IEEE Transactions on Biomedical Engineer-ing vol 59 no 12 pp 3083ndash3089 2012

[6] L-J Xu Y-X Guo and W Wu ldquoMiniaturised slot antenna forbiomedical applicationsrdquo Electronics Letters vol 49 no 17 pp1060ndash1061 2013

[7] F-J Huang C-M Lee C-L Chang L-K Chen T-C Yo andC-H Luo ldquoRectenna application of miniaturized implantableantenna design for triple-band biotelemetry communicationrdquoIEEE Transactions on Antennas and Propagation vol 59 no 7pp 2646ndash2653 2011

[8] A Kiourti and K S Nikita ldquoAccelerated design of optimizedimplantable antennas for medical telemetryrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 1655ndash1658 2012

[9] C-M Lee T-C Yo C-H Luo C-H Tu and Y-Z JuangldquoCompact broadband stacked implantable antenna for biote-lemetry with medical devicesrdquo Electronics Letters vol 43 no12 pp 660ndash662 2007

[10] K Scholten and E Meng ldquoMaterials for microfabricatedimplantable devices a reviewrdquo Lab on a ChipmdashMiniaturisationfor Chemistry and Biology vol 15 no 22 pp 4256ndash4272 2015

[11] T Sun X Xie and ZWangWireless Power Transfer for MedicalMicrosystems Springer 2013

[12] D-W Seo J-H Lee and H-S Lee ldquoOptimal coupling toachieve maximum output power in a WPT systemrdquo IEEETransactions on Power Electronics vol 31 no 6 pp 3994ndash39982016

[13] D-W Seo S-T Khang S-C Chae J-W Yu G-K Lee andW-S Lee ldquoOpen-loop self-adaptive wireless power transfer systemfor medical implantsrdquo Microwave and Optical Technology Let-ters vol 58 no 6 pp 1271ndash1275 2016


[14] D-W Seo J-H Lee and H Lee ldquoStudy on two-coil andfour-coil wireless power transfer system using z-parameterapproachrdquo ETRI Journal vol 38 no 3 pp 568ndash578 2016

[15] K Lee and D-H Cho ldquoSimultaneous information and powertransfer using magnetic resonancerdquo ETRI Journal vol 36 no 5pp 808ndash818 2014

[16] A Khripkov W Hong and K Pavlov ldquoIntegrated resonantstructure for simultaneous wireless power transfer and datatelemetryrdquo IEEE Antennas andWireless Propagation Letters vol11 pp 1659ndash1662 2012

[17] C R Paul Inductance Loop and Partial John Wiley amp SonsNew York NY USA 2010

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Submit your manuscripts athttpwwwhindawicom

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SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



ECG sensor

Base-stationBluetooth

Personal terminal

MICS bandcommunications

WPT using ISM band

Figure 1 The concept developing the ECG monitoring system

Epidermis

Dermis

Fat

Muscle

Magnetic field

Outside body

MICS ant

MICS ant

Rx resonantcoil

Tx resonantcoil

EM field

2mmndash3 cm

11ndash3mm

003ndash013mm

Figure 2 Inductive and electromagnetic links between the implantdevice and base-station

tradeoff exists between the PTE and data rate In order toovercome these disadvantages the power allocation strategyusing an orthogonal frequency-division multiplexing systemis suggested [15] However in most recent researches theWPT system operates at the industrial scientific medical(ISM) band such as 678MHz and 1356MHz to easilyimplement a resonant coil with high 119876-factor and usesthe outband communications to achieve the high datarate

Our group has developed an ECG monitoring system asshown in Figure 1 An implant device communicates with abase-station using the MICS frequency band and transfersthe sensed ECG signals to the exterior base-station Con-secutively the collected ECG signals can be sent wirelesslyto a personal terminal via Bluetooth On the other handthe power is wirelessly transferred from the base-station tothe implant device at 1356MHz That is the base-stationof the ECG monitoring system transfers simultaneously thepower and signal into the implantable medical device usingthe outband communications

Because the ECG signals are detected in the skin layerthe implant device is usually inserted in the subcutaneous fatlayer for the ECG monitoring system as shown in Figure 2and then the implant depth is about 3mm to 20mm Inour design concept the implant device should have a bar-type shape in order to minimize the skin incision part andthe height of the implant board should be low to minimizethe foreign body sensation of skin In the MICS bandthe transmit power has to be less than 25120583W (minus16 dBm)and the MICS antenna should have the gain greater than

minus45 dBi from the link budge analysis to achieve theminimumcommunication distance of 2m On the other hand thegap between two electrodes of the ECG sensor should belarger than 30mm in order to capture the stable ECG signalTherefore the implant coil size is set to 30mm times 5mmwhile there is no size limit for the external coil Since thepower is transferred from the external coil to the implantcoil only when the secondary battery needs charging theexternal coil connected with the base-station is put on theskin or clothes only under chargingTherefore themaximumdistance between two coils is about 20mm In additionbecause the implant device receives the signal and powersource from the exterior base-station the resonant coil andMICS antenna should be located on the outward surface ofthe implant device

In [16] the Rx resonator operating at 678MHz integratedwith an antenna for theMICS band is proposed Inserting theferrite material below the coil generates the antenna currentpath However the height of integrated resonator and MICSantenna is not low due to the ferrite material

In this study integration of the coil and antenna on a com-mon substrate is proposed for the implant device with lowprofile Particularly unlike most of the MICS antennas usingsubstrate with high permittivity the multilayer substrate ofthe ferrite sheet and FR-4 is utilized for significant size-reductionTheir potentials for the applications are verified bysimulations and experiments

In the following we first present the proposed integrationgeometry of the resonant coil and MICS antenna We thengive details about design of integrated resonant coil withMICS antenna And then we describe the development oftissue-emulating materials that are used for in vitro mea-surements Finally we present simulation and measurementresults

2 Geometry of Resonant Coil andMICS Antenna

Figure 3 shows the configuration of the proposed integrationof the Rx resonant coil and MICS antenna for the ECGmonitoring system The integration pattern module has asize of 225mm3 (30mm times 5mm times 15mm) A conductingmeandered PIFA and upper coil pattern are printed on a08mm thick FR-4 substrate (120576

119903= 44 tan 120575 = 0013) and

the lower coil pattern is printed on the bottom of the FR-4substrate To isolate the implant device from the conductivetissue the quartz superstrate (120576

119903= 378) packages the implant

device The ferrite sheet is inserted between the FR-4 and theground plane to shorten the effective wavelength and shieldmagnetic field interfering with the other circuits

As it can be observed from Figure 3(b) the prototype ofthe implant device consists of the bottom circuit module andtop integration pattern module The circuit module includestheMICS transceiver ECG sensor part impedance matchingnetwork and charge circuit The integration pattern moduleis the resonant coil integrated with the MICS antenna ofFigure 3(a) The connection between the two modules isrealized and fixed with a low-profile connector


Rx coil Rx antenna

FR4

Ferrite sheetGround

30mm

5mm

(a)



3mm

5mm

30mm

(b)








Start

Design the Rx coil



factor

End


YesNo

Desired Q-



30mm

5m

mlguard

lwidth Rxlgap Rx

l1

l2l3l4

(a)Quartz

FR-4



hquartzhsubhferrite

(b)






lshortlfeed

lw ant

l1l1l2 l3

Want

(a)

Quartz

FR-4


Lower layerVia hole


Shorting pin

Feeding pin

coil pattern

(b)

30mm

5m

m





1 1198972 and 119897

3) related







119872 = 120583

0radic119903Rx119903Tx [(

2

119896

minus 119896)119870 (119896) minus

2

119896

119864 (119896)] (1)

d

30mm

5mm

lguardlwidth Tx

lgap Tx

WTxDTx



119896

2

=

4119903Rx119903Tx

(119903Rx + 119903Tx)2

+ 119889

2

(2)


120597119896

120597119886

= 0 997904rArr 119903Tx = radic

119903

2

Rx + 1198892

(3)









powder ww H2O ww


Agilent E4991A

Agilent 85070E

Samples

Agilent 85070

E4991A option 010




119903=

28525 and 120590 = 0238 Sm at 1356MHz and 120576

119903= 467 and





6 Conclusion


Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

00

05

10

15

20

Con

duct

ivity

(Sm

)

0

100

200

300

400

500

15 20 25 30 35 40 45 5010Frequency (MHz)

(a)

Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

30

35

40

45

50

55

60

00

05

10

15

20

Con

duct

ivity

(Sm

)

350 400 450 500300Frequency (MHz)

(b)




119871 nH 5952 6056119877Ω 259 21119876 196 2457119896 0034 0035120578 19 21


MeasuredSimulated

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Refle

ctio

n co

eff (

dB)

250 300 350 400 450 500 550 600200Frequency (MHz)

(a)

030

60

90

120

150180

210

240

270

300

330

xz-plane (120601 = 0∘)

yz-plane (120601 = 90∘)

minus40

minus45

minus50

minus55

minus50

minus45

minus40

(b)




Competing Interests


Acknowledgments


References





















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Rx coil Rx antenna

FR4

Ferrite sheetGround

30mm

5mm

(a)



3mm

5mm

30mm

(b)








Start

Design the Rx coil



factor

End


YesNo

Desired Q-



30mm

5m

mlguard

lwidth Rxlgap Rx

l1

l2l3l4

(a)Quartz

FR-4



hquartzhsubhferrite

(b)






lshortlfeed

lw ant

l1l1l2 l3

Want

(a)

Quartz

FR-4


Lower layerVia hole


Shorting pin

Feeding pin

coil pattern

(b)

30mm

5m

m





1 1198972 and 119897

3) related







119872 = 120583

0radic119903Rx119903Tx [(

2

119896

minus 119896)119870 (119896) minus

2

119896

119864 (119896)] (1)

d

30mm

5mm

lguardlwidth Tx

lgap Tx

WTxDTx



119896

2

=

4119903Rx119903Tx

(119903Rx + 119903Tx)2

+ 119889

2

(2)


120597119896

120597119886

= 0 997904rArr 119903Tx = radic

119903

2

Rx + 1198892

(3)









powder ww H2O ww


Agilent E4991A

Agilent 85070E

Samples

Agilent 85070

E4991A option 010




119903=

28525 and 120590 = 0238 Sm at 1356MHz and 120576

119903= 467 and





6 Conclusion


Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

00

05

10

15

20

Con

duct

ivity

(Sm

)

0

100

200

300

400

500

15 20 25 30 35 40 45 5010Frequency (MHz)

(a)

Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

30

35

40

45

50

55

60

00

05

10

15

20

Con

duct

ivity

(Sm

)

350 400 450 500300Frequency (MHz)

(b)




119871 nH 5952 6056119877Ω 259 21119876 196 2457119896 0034 0035120578 19 21


MeasuredSimulated

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Refle

ctio

n co

eff (

dB)

250 300 350 400 450 500 550 600200Frequency (MHz)

(a)

030

60

90

120

150180

210

240

270

300

330

xz-plane (120601 = 0∘)

yz-plane (120601 = 90∘)

minus40

minus45

minus50

minus55

minus50

minus45

minus40

(b)




Competing Interests


Acknowledgments


References





















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










lshortlfeed

lw ant

l1l1l2 l3

Want

(a)

Quartz

FR-4


Lower layerVia hole


Shorting pin

Feeding pin

coil pattern

(b)

30mm

5m

m





1 1198972 and 119897

3) related







119872 = 120583

0radic119903Rx119903Tx [(

2

119896

minus 119896)119870 (119896) minus

2

119896

119864 (119896)] (1)

d

30mm

5mm

lguardlwidth Tx

lgap Tx

WTxDTx



119896

2

=

4119903Rx119903Tx

(119903Rx + 119903Tx)2

+ 119889

2

(2)


120597119896

120597119886

= 0 997904rArr 119903Tx = radic

119903

2

Rx + 1198892

(3)









powder ww H2O ww


Agilent E4991A

Agilent 85070E

Samples

Agilent 85070

E4991A option 010




119903=

28525 and 120590 = 0238 Sm at 1356MHz and 120576

119903= 467 and





6 Conclusion


Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

00

05

10

15

20

Con

duct

ivity

(Sm

)

0

100

200

300

400

500

15 20 25 30 35 40 45 5010Frequency (MHz)

(a)

Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

30

35

40

45

50

55

60

00

05

10

15

20

Con

duct

ivity

(Sm

)

350 400 450 500300Frequency (MHz)

(b)




119871 nH 5952 6056119877Ω 259 21119876 196 2457119896 0034 0035120578 19 21


MeasuredSimulated

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Refle

ctio

n co

eff (

dB)

250 300 350 400 450 500 550 600200Frequency (MHz)

(a)

030

60

90

120

150180

210

240

270

300

330

xz-plane (120601 = 0∘)

yz-plane (120601 = 90∘)

minus40

minus45

minus50

minus55

minus50

minus45

minus40

(b)




Competing Interests


Acknowledgments


References





















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













powder ww H2O ww


Agilent E4991A

Agilent 85070E

Samples

Agilent 85070

E4991A option 010




119903=

28525 and 120590 = 0238 Sm at 1356MHz and 120576

119903= 467 and





6 Conclusion


Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

00

05

10

15

20

Con

duct

ivity

(Sm

)

0

100

200

300

400

500

15 20 25 30 35 40 45 5010Frequency (MHz)

(a)

Rela

tive p

erm

ittiv

ity (120576

r)


Measured 120590

Desired 120590

30

35

40

45

50

55

60

00

05

10

15

20

Con

duct

ivity

(Sm

)

350 400 450 500300Frequency (MHz)

(b)




119871 nH 5952 6056119877Ω 259 21119876 196 2457119896 0034 0035120578 19 21


MeasuredSimulated

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Refle

ctio

n co

eff (

dB)

250 300 350 400 450 500 550 600200Frequency (MHz)

(a)

030

60

90

120

150180

210

240

270

300

330

xz-plane (120601 = 0∘)

yz-plane (120601 = 90∘)

minus40

minus45

minus50

minus55

minus50

minus45

minus40

(b)




Competing Interests


Acknowledgments


References





















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










MeasuredSimulated

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Refle

ctio

n co

eff (

dB)

250 300 350 400 450 500 550 600200Frequency (MHz)

(a)

030

60

90

120

150180

210

240

270

300

330

xz-plane (120601 = 0∘)

yz-plane (120601 = 90∘)

minus40

minus45

minus50

minus55

minus50

minus45

minus40

(b)




Competing Interests


Acknowledgments


References





















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









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Research Article Integration of Resonant Coil for Wireless ...downloads.hindawi.com/journals/ijap/2016/7101207.pdf · the biomedical implant devices, such as capsule endoscope, pacemaker,