RF link for Implanted Medical Devices (IMDs) and Sub-GHz Inductive Power Transmission

(1)

HAL Id: hal-01692423

https://hal.archives-ouvertes.fr/hal-01692423

Submitted on 25 Jan 2018

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RF link for Implanted Medical Devices (IMDs) and

Sub-GHz Inductive Power Transmission

Antoine Diet, Satvros Koulouridis, Yann Le Bihan, Quang-Trung Luu, Olivier

Meyer, Lionel Pichon, Marc Biancheri-Astier

To cite this version:

Antoine Diet, Satvros Koulouridis, Yann Le Bihan, Quang-Trung Luu, Olivier Meyer, et al.. RF link for Implanted Medical Devices (IMDs) and Sub-GHz Inductive Power Transmission. Journées d’Etude sur la TéléSANté, 6ème edition, Pôle Capteurs, Université d’Orléans, May 2017, Bourges, France. �hal-01692423�

(2)

RF link for Implanted Medical Devices (IMDs)

and Sub-GHz Inductive Power Transmission

A. Diet

1 , S. Koulouridis

1,2

, Y. Le Bihan

1 , Q.-T. Luu

1 , O. Meyer

1 , L. Pichon

1 , M. Biancheri-Astier

1

1 _{GeePs | Group of electrical engineering - Paris, UMR CNRS 8507, CentraleSupélec, Univ. Paris-Sud, Université Paris-Saclay,}

Sorbonne Universités, UPMC Univ Paris 06, 3 & 11 rue Joliot-Curie, Plateau de Moulon 91192 Gif-sur-Yvette CEDEX, France

2 _{School of Electrical and Computer Engineering, University of Patras, Patras, Greece.}

antoine.diet@geeps.centralesupelec.fr, koulouridis@g.upatras.gr

Simulation

1 Power Transfer Efficiency (PTE)

Coupling coefficient

Q-factor of Tx coil

_{Loaded Q-factor of Rx coil}

Rx internal efficiency

Equivalent circuit using Z-matrix as the wireless link between Tx and Rx coil

[D. Ahn et al., Optimal Design of Wireless Power Transmission Links for Millimeter-Sized Biomedical Implants,

IEEE Trans. Biomed. Circuits Syst., pp. 1–13, 2014.]

Rx Part

Tx Part

Coupling link

Receiver power reception susceptibility:

How strongly the implant can receive power

under a given magnetic filed exposure

Transmitter figure-of-merit

How strongly the transmitter

coupled with the receiver

In-body

Off-body

ε(ω) = ε’(ω) – j ε’’(ω)

ZA1

ZB

ZA2

ZD1

ZD2



 



1 open

short

1 open

meas.

deemb.

Y



1 



ZE1

ZE2

VNA measurements

« gives »

Y

_open

VNA measurements

« gives »

Y

_short

VNA measurements

« gives »

M

L

₁

L

₂

meas.

Y

deemb.

Y

PORT 1

(VNA)

PORT 2

(VNA)

5-turns coil

_{...or « SHORT », or OPEN}

SMA

cable

SMA

cable

1 mm height

1,25 mm radius

FROM

CONTEXT

TO

EM

MODELLING

ε(ω) = ε’(ω) – j ε’’(ω)

Configuration of the Tx and Rx coil

Parameter

Tx coil

Rx coil

Radius

12 mm

0.5 mm

Height

1 mm

Number of turns

1

7 Distance between two coils

12 mm

Configuration of the tissue model

Parameter

Skin Muscle

Bone

Thickness (mm)

2.5

25

22.5 µ

_r

1

1 ρ (kg/m

3 ₎

₁₁₀₀

₁₀₄₁

₁₈₅₀

Therm. Cond. (W/K/m)

0.293

0.53

0.41 Blood flow (W/K/m

3 ₎

₉₁₀₀

₂₇₀₀

₃₄₀₀

- IMDs  high impact of the body on EM fields (modelling

needed with ε’ and ε’’) + radiating and non-radiating modes

- Design of helical RX coils  impacted by the body, lowering

performances (need a figure of merit, see PTE)

- OPTIMAL frequency, mainly due to body

losses and dispersion effects

- OPTIMAL size and orientation, due to the

distribution of H and E

-

...for deembedding connector effects (size

and frequency)

-

...for deembedded measurements in

presence of the phantom (in progress)

-

...for an accurate control of the position

The measurements show an

interesting agreement for

self-inductance evaluation under 300

MHz with a simple calibration test

fixture. Some parasitic elements are

still present after deembedding and

we need to improve the design of

the test fixture to be able to

evaluate the whole impedance

matrix of the 2 coils system.

The design of the coils in the

presence of a biological tissue can

be

fruitfully

helped

with

measurements of the coil inside a

phantom made with Triton X, water

and salt.

This

phantom

relative

permittivity and conductivity are

also given in function of the

frequency. Next step of the design

process is to accurately deembed

and re-simulate to match the

characteristics of the medium for

optimization of the small coils.

Bone (22.5 mm) Muscle (25 mm) Skin (2.5 mm)

Human arm

Rx coil Tx coil Muscle (25 mm)

100 mm

3

0

0 m

m

d

Muscle

Bone

Rx coil Tx coil

Human arm

Rx coil Tx coil

Human arm

top view

front view

Skin

0.00

50.00

100.00

150.00

0 .0

1

0 .0

6

0 .1

1

0 .1

6

0 .2

1

0 .2

6

0 .3

1

0 .3

6

0 .4

1

0 .4

6

0 .5

1

0 .5

6

0 .6

1

0 .6

6

0 .7

1

0 .7

6

0 .8

1

0 .8

6

0 .9

1

0 .9

6 ε'

Frequency (GHz)

permittivity vs freq

Eps_1

Eps_2

Eps_3

Eps_4

0.00

0.20

0.40

0.60

0.80

0 .0

1

0 .0

6

0 .1

1

0 .1

6

0 .2

1

0 .2

6

0 .3

1

0 .3

6

0 .4

1

0 .4

6

0 .5

1

0 .5

6

0 .6

1

0 .6

6

0 .7

1

0 .7

6

0 .8

1

0 .8

6

0 .9

1

0 .9

6 co

n

d

u

ct

iv

it

y

Frequency (GHz)

conductivity vs freq

Cond_1

Cond_2

Cond_3

Cond_4

Phantom made by 28 % triton X – water - salt

VNA 4 ports

Rx coil

Tx coil

5 cm

co

n

d

u

ct

iv

it

y

(S

/m

)

Relative permittivity vs. frequency

6

7

8

9

10

11

12

13

14

1

2

3

4

5

6

7 Tx coil



s radius (mm)

P T E ( % )

Sweeping R

Tissue Sim.

Air Sim.

1.9145 %, 105.8 MHz

6.8265 %, 284.9 MHz

6

7

8

9

10

11

12

13

14

1

2

3

4

5

6

7 Tx coil



s radius (mm)

P T E ( % )

Sweeping R

Tissue Sim.

Air Sim.

1.9145 %, 105.8 MHz

6.8265 %, 284.9 MHz

0

50

100

150

200

250

300

0

1

2

3

4

5

6

7 Frequency (MHz)

P T E

Power Transfer Efficiency

Tissue Sim.

Air Sim.

1.5908 %, 86.813 MHz

6.8427 %

284.452 MHz

0

50

100

150

200

250

300

0

1

2

3

4

5

6

7 Frequency (MHz)

P T E

Power Transfer Efficiency

Tissue Sim.

Air Sim.

1.5908 %, 86.813 MHz

6.8427 %

284.452 MHz

CURRENT WORK AND CONCLUSION

PTE

TEST FIXTURE NEEDED:

Using only two coils,

Implanted depth: 10 mm

0.5 1 1.5 2 2.5 3 3.5 4 4.5 x 108 3 4 5 6 7 8 9 10 11 x 10-8 self-inductance on Z11 and Z22 analytical evaluation

deembeddeb measurements, port 2 deembeddeb measurements, port 1

0.5 1 1.5 2 2.5 3 3.5 4 4.5 x 108 3 4 5 6 7 8 9 10 11 x 10-8 self-inductance on Z11 and Z22 analytical evaluation