Paper presentation – Ultra-Portable Devices

Paper:

Presented by:

S.K.S. Gupta, S. Lalwani, et al., “Towards a propagation model

for wireless biomedical applications”, IEEE International

Conference on Communications, 2003. ICC '03, Page(s): 1993 -

1997 vol.3, 2003

Rohit Chandra

2010-05-09 1Paper Presentation - Ultra Portable Devices

Outline

• Propagation in Free Space Vs. Human tissue

• Power in Propagation of EM waves in Human Tissue Absorbed Power: Near Field(NF) and Far Field (FF)

Received Power: NF and FF

• Simulation Results

• Experimental Results

• Summary

2010-05-09 2Paper Presentation - Ultra Portable Devices

Free Space Vs. Human tissue

Propagation

2010-05-09 3Paper Presentation - Ultra Portable Devices

n

d

1

Rate at which Rx Power

decreases.

Other Loss: fading due

to multipath.

Model Eg.: Okumura

Hata , 2 Ray Model

Free Space Human Tissue

Coefficient of path loss ?

Losses: Due to

absorption of power in

tissues (dissipated as

heat SAR),

attenuation due to lossy

medium

Absorbed Power

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20 d

Hertzian Dipole

Power Absorbed = PNF + PFF

Derivation of Power

• SAR in Near field: depends on

Magnetic field

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KgwattsHcSAR rmscorrNF /1 22

222

Correction factor to take into

account changed reflection

at small distances

Reflection coefficient

( zero in this case as both Tx and Rx in

same homogenous medium)

RMS value of H field

Derivation of Power [contd..]

• PNF average SAR over the entire tissue in NF

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0

0

2

0

d

rR

NF PP

dVSARNF

Derivation of Power [contd..]

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KgwattsESAR rmsFF /2

d

dR

NF PP

0 0

2

0

dVSARFF

• SAR in FF depends upon Electric Field

Received Power

• In NF: No general formula; based on measurement; some

approximation for dipoles and monopoles

• In FF: Power density depends upon distance.

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eNFT

R AL

PPP

2

)(16

rtFFNFT

R GGd

PPPP

2

2

4

)(

Simulation Results

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Experiement Results

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PMBA vs Free Space Pathloss

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• Additional 30-35 dB loss in PMBA

Summary

• Power absorbed in near field has to be taken into account

while calculating Pathloss inside human tissues.

• Path Loss Model has been developed for propagation inside

homogeneous tissues (PMBA)

• Friis Formula is special case with near field and far field

absorption loss equal to zero.

2010-05-09 12Paper Presentation - Ultra Portable Devices