VNTélécom'09

Characterization of the diffusion of Characterization of the diffusion of electromagnetic waves by an urban electromagnetic waves by an urban

environment in X-bandenvironment in X-band

Presentator: Ngoc Truong Minh NGUYENNgoc Truong Minh NGUYEN

DRE/L2S (Supélec) - 3 rue Joliot Curie, 91192 Gif-sur-DRE/L2S (Supélec) - 3 rue Joliot Curie, 91192 Gif-sur-YvetteYvette

L2E (UPMC) - 4 place Jussieu, 75006 ParisL2E (UPMC) - 4 place Jussieu, 75006 Paris

mail:mail: nnguyen@lss.supelec.fr -- tel:tel: 01.69.85.15.7101.69.85.15.71

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Context and Context and objectivesobjectives

zz TransmiTransmittertter

ReceiverReceiver

xx

yy

φφφφ’’

θθ’’

θθ

R’R’RR

OO

ContextContext- Remote sensing:Remote sensing: is the measurement/acquisition of the information about an object or a is the measurement/acquisition of the information about an object or a

phenomenon by the no contact measuring between an instrument (usually a RADAR) and the phenomenon by the no contact measuring between an instrument (usually a RADAR) and the

object.object.

Instrument de mesureInstrument de mesure- SAR (Synthetic Aperture Radar):SAR (Synthetic Aperture Radar): bistatic (transmitter and receiver are different) can bistatic (transmitter and receiver are different) can

overcome the limitations of conventional monostatic radar (non-discrete, easily confused ...) overcome the limitations of conventional monostatic radar (non-discrete, easily confused ...)

for the natural scene imageries or targets detection.for the natural scene imageries or targets detection.

- This justifies our study of the diffusion bistatic by an urban area.- This justifies our study of the diffusion bistatic by an urban area.

ObjectivesObjectives- The aim of the The aim of the

thesis is to thesis is to develop develop

3D models of cities3D models of cities to to

study the diffusion in study the diffusion in

X-band (8 - 12 GHz).X-band (8 - 12 GHz).

- It takes into account - It takes into account

the multiple the multiple

reflections caused by reflections caused by

the soil and buildings the soil and buildings

and diffractions by and diffractions by

the edges of the edges of

buildings.buildings.

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• Representation of urban areasRepresentation of urban areas• Rays-tracing and UTDRays-tracing and UTD• ResultsResults• PerspectivesPerspectives

ContentContentss

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• Representation of urban Representation of urban areasareas

• Rays-tracing and UTDRays-tracing and UTD• ResultsResults• PerspectivesPerspectives

How to define an urban How to define an urban area ?area ?

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Representation of urban Representation of urban areasareas

An urban area sizes LAn urban area sizes Lx x x x LLyy

• buildings: a set of randomly distributed rectangular parallelepipeds in this buildings: a set of randomly distributed rectangular parallelepipeds in this

zonezone

• ground: a smooth dielectric surface ground: a smooth dielectric surface (weak roughness compared to the used (weak roughness compared to the used

wavelength)wavelength)

• streets: distances between the buildingsstreets: distances between the buildings

Electromagnetic characteristicsElectromagnetic characteristics

• street (index r): street (index r): εεrr, , μμrr = = μμoo = 4π.10 = 4π.10-7-7 H / m H / m

• buildings (index b): buildings (index b): εεbb, , μμbb = = μμoo = 4π.10 = 4π.10-7-7 H H

/ m/ mLxLx

LyLy

εεrr

μμrr

εεbb

μμbb

xx

zz

OO

yy

VNTélécom'09

• Representation of urban Representation of urban areasareas

• Rays-tracing and UTDRays-tracing and UTD• ResultsResults• PerspectivesPerspectives

Find methods to Find methods to use ?use ?

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Rays-tracing and Rays-tracing and UTDUTD

kk

ii

LOILOI

DihedrDihedralal

''Zone Zone 33

Zone Zone 22

Zone Zone 11

LORLOR

incident incident fieldfield++diffracted diffracted fieldfield

diffracted diffracted fieldfield

incident incident fieldfield

++reflected reflected

fieldfield++

diffracted diffracted fieldfield

LOR (Limit Of LOR (Limit Of Reflection Reflection field)field)

LOI (Limit Of LOI (Limit Of Incident field)Incident field)

Face

Face

OO

Face

Face

nn

OO

xx

yy

zz

LLxx

LLyy

Geometrical Geometrical Optic Optic

Geometrical Theory of the Geometrical Theory of the DiffractionDiffraction

mathematical mathematical discontinuitiesdiscontinuities

Uniform Theory of the Uniform Theory of the DiffractionDiffraction

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• Representation of urban Representation of urban areasareas

• Rays-tracing and UTDRays-tracing and UTD• ResultsResults• PerspectivesPerspectives

Hmm… How about the Hmm… How about the results ?results ?

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ResultResultss

• Problem:Problem: Calculate the Calculate the diffracted field by the diffracted field by the reflection (one or multiple) reflection (one or multiple) on the soil or the buildings on the soil or the buildings and/or the diffraction on the and/or the diffraction on the edges of the buildings.edges of the buildings.

Four buildingsFour buildings• heights H = [8 14 10 12] heights H = [8 14 10 12] mm• length L = [5 6 5 6] mlength L = [5 6 5 6] m• width W = [4 5 7 8] mwidth W = [4 5 7 8] m• εεbétonbéton = 7.31-j*0.36 = 7.31-j*0.36

• εεsolsol = 28.51-j*12.84 = 28.51-j*12.84

• Transmitter:Transmitter: ii = 28°, = 28°, φφii = =

70°, sizes x = 20m, y = 20m70°, sizes x = 20m, y = 20m

• Receiver:Receiver: rr = 30°, = 30°, φφrr = =

270°, sizes x270°, sizes xrr = 100m, y = 100m, yrr = =

100m100m

• Two radars placed at the Two radars placed at the

same height (100m)same height (100m)

xx

xx

yy

zz

OO

LLxx

LLyy

Transmitt

Transmitt

erer

Receiver

Receiverrr

φφrr

ii

φφii

yy

xxrr

yyrr

εεbétonbéton

μμoo

εεsolsol

μμoo

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The rays influenced The rays influenced

by one diffraction by one diffraction

then a reflection on then a reflection on

the soilthe soil

The rays influenced by The rays influenced by

one diffraction and two one diffraction and two

reflections reflections

The direct diffraction The direct diffraction

raysrays

ResultResultss

Rayo

n

Rayo

n

inci

dent

inci

dent

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ResultResultss

Polarisation Polarisation VVVV

Polarisation Polarisation HVHV

•The incident electromagnetic waveplane at frequency 10 GHz and | EThe incident electromagnetic waveplane at frequency 10 GHz and | Eincinc | = | = 1 V / m1 V / m

Max |EMax |EVvVv|² = 13.69 |² = 13.69 dBmdBm

Min |EMin |EVvVv|² = -106.31 |² = -106.31 dBmdBm

Max |EMax |EHvHv|² = 3.70 dBm|² = 3.70 dBm

Min |EMin |EHvHv|² = -116.30 |² = -116.30 dBmdBm

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ResultResultss

Polarisation Polarisation HHHH

Polarisation Polarisation VHVH

• The contribution comes mainly from the field due to The contribution comes mainly from the field due to multiple reflectionsmultiple reflections, the contribution , the contribution

of diffracted rays is lower.of diffracted rays is lower.

Max |EMax |EHhHh|² =|² = 14.32 14.32 dBmdBm

Min |EMin |EHhHh|² = -105.68 |² = -105.68 dBmdBm

Max |EMax |EVhVh|² = 4.29 dBm|² = 4.29 dBm

Min |EMin |EVhVh|² = -118.60 |² = -118.60 dBmdBm

VNTélécom'09

• Representation of urban Representation of urban areasareas

• Rays-tracing and UTDRays-tracing and UTD• ResultsResults• PerspectivesPerspectives

PPerspectiverspectiveses

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PerspectivPerspectiveses

• To obtain an average value of the diffused field in a given direction, it should be calculated To obtain an average value of the diffused field in a given direction, it should be calculated

several possible configurations for the broadcast and then generate the average field.several possible configurations for the broadcast and then generate the average field.

• The applications are:The applications are:

- Characterization of the diffracted field by arbitrary urban zones. Characterization of the diffracted field by arbitrary urban zones.

- SAR imageries or targets detection in this environment.SAR imageries or targets detection in this environment.

VNTélécom'09

BibliographiesBibliographies

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imaging Urban area’’, Electronics Letters, 34(11): 1147-1149, mai 1998imaging Urban area’’, Electronics Letters, 34(11): 1147-1149, mai 1998

2- J.M. Berenyi Tajbakhsh, M.J. Kim and R.E. Burge,’’Images of urban areas by a synthetic aperture 2- J.M. Berenyi Tajbakhsh, M.J. Kim and R.E. Burge,’’Images of urban areas by a synthetic aperture

radar simulator’’, Conf. on SAR data processing for remote sensing, Rome, Italy, p.290-300, radar simulator’’, Conf. on SAR data processing for remote sensing, Rome, Italy, p.290-300,

septembre 1974septembre 1974

3- R .J. Luebbers,’’Finite conductivity uniform GTD versus knife edge diffraction in prediction of 3- R .J. Luebbers,’’Finite conductivity uniform GTD versus knife edge diffraction in prediction of

propagation path loss’’, Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988], p.70-propagation path loss’’, Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988], p.70-

76, janvier 198476, janvier 1984

4- R.G. Kouyoumjian,’’A uniform geometrical theory of diffraction for an edge in a perfectly 4- R.G. Kouyoumjian,’’A uniform geometrical theory of diffraction for an edge in a perfectly

conducting surface’’, Proc. IEEE 62, p.1448-1461, novembre 1974conducting surface’’, Proc. IEEE 62, p.1448-1461, novembre 1974