SVM-based Classification Approach for Synthetic-Impulse Microwave Imaging

UNIVERSITY

OF TRENTO

DIPARTIMENTO DI INGEGNERIA E SCIENZA DELL’INFORMAZIONE

38050 Povo – Trento (Italy), Via Sommarive 14

http://www.disi.unitn.it

SVM-

BASED

C

LASSIFICATION

A

PPROACH FOR

S

YNTHETIC

-I

MPULSE

M

ICROWAVE

I

MAGING

F. Viani, M. Benedetti, M. Donelli, L. Lizzi, A. Cresp, L. Aliferis, C.

Pichot, and A. Massa

April 2008

InformationandCommuni ation Te hnology Dept. Universityof Trento

ViaSommarive14,38050Trento,ITALY Phone+390461882057Fax +390461882093

E-mail: andrea.massaing.unitn.it

Contra t No. DIT-PRJ-08-005

Te hni al Report N. 1

SVM-based Classi ation Approa h for Syntheti -Impulse

Mi rowave Imaging

Problem Geometry F.Viani

(1)

,M.Benedetti

(1)

,M.Donelli

(1)

,L.Lizzi

(1)

, A.Cresp

(2)

,I.Aliferis

(2)

,C.Pi hot

(2)

, andA.Massa

(1)

(1)

DepartmentofInformationEngineering andComputerS ien e ELEDIAResear hGroup

UniversityofTrento,ViaSommarive14,38050Trento-Italy Tel.+39 0461882057,Fax. +390461882093

E-mail: andrea.massaing.unitn.it

(2)

Laboratoired'Ele tronique,AntennesetTélé ommuni ations(LEAT) UniversitédeNi e-SophiaAntipolis

250rueAlbertEinstein,06560Valbonne

Tél: +33(0)492942802,Fax: +33(0)492942812 E-mail: hristian.pi hotuni e.fr

1. Introdu tion 3

2. Des riptionof the ProblemGeometry 3

Surfa e-Penetrati Radar(SPR)isaimedatprovidinganimageoftheobje tsburiedinanina essiblehost

medium. Su has enariogenerallyo ursinmanyappli ations,rangingfromtothesear hofobje tsinthe

subsoil [1℄ to through-wallimaging(TWI) [2℄. Inorder to ee tivelyre onstru t an a urateimage of the

investigationarea,manymethodologiesbasedonx-rays,ultrasoni s,eddy urrents,ormi rowaveshavebeen

investigated. Insu haframework,mi rowaveimagingte hniques are verypromisingsin e ele tromagneti

elds at entimeterwavelenghts anpenetratenon-ideal ondu tormaterialsandareusuallylowpowerand

relativelyinexpensive.

Re ently, thanksto the developmentof ee tiveultrawideband(UWB) hardware, wideband mi rowave

imaging systems have been proposed. Compared to single-frequen y approa hes, su h systems allow to

olle ta wideramount ofinformation, sin e thes attered eld anbe measuredat dierentfrequen iesin

theworkingbandwidthand/orinthetime-domain. Inordertotakeadvantageofmulti-frequen ydata,signal

pro essingplaysakeyrole. Dierentte hniques ombiningpre-pro essingtreatmentsandmi rowaveimaging

are urrentlyused to onstru tanimageofas ene[3℄. Inaddition,time-reversal(TR) datapro essinghas

beenre entlyemployedinordertodete tpositionsofthetargetsinaSyntheti -ImpulseMi rowaveImaging

System(SIMIS)[4℄.

Insu haframeworkandwithintheGALILEO2008proje t,theresear hunits,ELEDIAUniv. Trento

and LEAT Univ. Ni e,are urrently involved in theintegration of aSVM-based lassi ationapproa h

intheSIMISforthere onstru tionofthepositionandtheshapeoftargets. Su hareportisfo usedonthe

des riptionofproblemgeometryaswellasofthespe i ationoftheSIMIS.

2 Des ription of the Problem Geometry

A set of

N

ir ular ylindri als attererswith bary enters

X

obj

n

, Y

obj

n

, n = 1, ..., N

, radius

r

n

andheight

h

obj

n

, n

= 1, ..., N

are lo ated inside an investigation area

D

I

. The

n

-th s atterer is hara terized by the

diele tri properties

(ǫ

r

, σ)

n

, while the relative permittivity and the ondu tivity of

D

I

are

ǫ

rD

and

σ

D

, respe tively. Themeasurementsystemislo atedoutside

D

I

asshowninFig. 1and onsistsofalineararray of

M

exponentialtaperedslot (ETS)antennas,equallyspa ed by

s

. Ea h antenna anbeusedeither asa transmitterorare eiver,so

M

2

measurementsareavailableifallthepossible ombinationsofemittingand

re eiving antennas are onsidered. In parti ular, when the

m

-th antennais both transmitter and re eiver the

S

11

(f )

ree tionparameterismeasured,otherwisethetransmittingparameter

S

21

(f )

is olle tedinthe frequen y range

f

min

< f < f

max

. Alternatively, an extra antenna an be used astransmitter while the

antennatypologiesandpositions an beemployedwithoutae tingthere eivingsystem. However,in su h

a aseonly

M S

21

(f )

parametersareavailable.

Themeasurementsareperformedbothwithandwithoutthes attererinordertoobtaindierentialdata,

whereinthe ontributionoftheenvironmentisremovedbysubtra tion.

As for the spe i ations of the SIMIS, the system olle ts the s attering measurements by means of

M

= 8

ETS antennas working in the frequen y band between

f

min

= 1.4 GHz

and

f

max

= 20 GHz

(Fig. 2). Ea hantenna anbeemployedasatransmittingandre eivingdevi ebymeansoftwoele trome hani al

mi rowave

1

-to-

M

multiplexers. Atwo-portve tornetworkanalyzerprovidesRFsignalto thetransmitting antennaandmeasuresree tionandtrasmission

S

parameters.

[1℄ H.S hubertandA. Kuznetsov,Dete tion of Explosives andLandmines: Methods andField Experien e.

KluwerA ademi Publishers,Boston,2001.

[2℄ D. D. Ferrisand N. C.Currie, A surveyof urrentte hnologies forthrough-wall-surveillan e(TWS), Pro . SPIE,vol.3577, pp.62-68,1998.

[3℄ D. J. Daniels, Ground Penetrating Radar, 2nded., IEERadar, Sonar,Navigationand Avioni sSeries.

TheInstitution ofEle tri alEngineers,London,2004.

[4℄ A. Cresp,I.Aliferis, M. J.Yedlin, C. Pi hot, and J.-Y. Dauvigna , Investigation oftime-reversal

pro- essing for surfa e-penetrating radar dete tion in a multiple-target onguration, submitted to 2008

x

O1

Y

obj

1

Y

obj

2

s

r1

(ǫr, σ)1

X

₁

obj

X

₂

obj

r2

(ǫr, σ)2

O2

...

m

...

M

0

1

x

h

obj

2

z

y

DI

h

obj

₁