Caratterizzazione della RCS di Pedoni nelle Bande 23-28 GHz e 76-81 GHz Joaquim Fortuny-Guasch, Jean-Marc Chareau Institute for the Protection and Security of the Citizen European Commission Joint Research Centre, Ispra- Italy

Seminario RF e Microonde Giovedi' 8 Maggio Museo Nazionale della Scienza e della Tecnologia Milano, 8 Maggio 2014

Outline

• • • • • • • •

Test facility Measurement setup Test scenarios Calibration System performance List of dummies Results Conclusion

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Test facility Measurement campaign was carried out at the European Microwave Signature Laboratory (EMSL) Joint Research Centre (JRC), Ispra, Italy

Large size anechoic chamber was specifically prepared: • Target positioner lowered down to 1 m • A few square meters of absorber removed • Instrumentation installed inside the chamber • Possibility to hang dummies

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Measurement Setup Two bands measured at the same time ! • Quasi-monostatic configuration • Vertical polarisation

RCS measurements in the 23-28 GHz band: • 50 GHz Network analyser • Coax-to-waveguide adaptors • Standard gain horns (20 dB) RCS measurements in the 76-81 GHz band: • 67 GHz Network analyser with mm extension • Millimeter-Wave controller • E-band mm-wave heads • Standard gain horns (20 dB)

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Test scenarios EMSL software controls only one instrument EMSL+ independent software created Sweep sync with hardware trigger

Azimuth scan 360°/ 5°steps in 5 min for humans 360°/ 1°steps in 20 min for dummies 76-81 GHz sweep in 250 ms (10 kHz IF BW) 23-28 GHz sweep in 200 ms (15 kHz IF BW) Antenna heights 0.45 / 0.8 / 1.0 m

Start EMSL+

Start EMSL

Init PNA

Init PNA-X

23-28 GHz

76-81 GHz

Set angle PNA-X Soft Trigger Read/Save Data

TRIG

Wait PNA Ext Trigger Read/Save Data

Last step ?

Last step ?

End

End

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Bistatic vs Monostatic RCS • 15 cm separation distance between tx/rx antennas, at 3.4 m means 2 deg bistatic angle • Example of a dihedral corner reflector vs sphere • Corner reflectors not appropriate because of influence of bistatic angle

a b 3 dB Beamwidth < 2o

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Calibration of RCS Data • Phase Calibration made using a circular disc (12 cm diam) • Precise amplitude calibration made with a metal sphere (3 in diam)

Offset = 1.41 dB

• • • •

Offset = 2.7 dB

Calibration works better at 24 GHz because of the higher SNR (expected) RMS calibration errors are 0.46 dB at 24 GHz and 0.58 dB at 77 GHz Sphere shows the same RCS (~-24 dBsm) at 24 and 77 GHz The only con is its low RCS compared with disc and dihedral/trihedral reflectors 7

System performance – Signal-to-background ratio Average spectrum 23-28 GHz sweep 60 With a target Empty room 50

Magnitde (dB)

40

30

20

Signal-to-background ratio > 30 dB in 23-28 GHz band

10

0 0

2

4

6

8

10 range (m)

12

14

16

18

20

Average spectrum 76-81 GHz sweep

60

With a target Empty room

Magnitude (dB)

50

40

30

20

Signal-to-background ratio > 27 dB in 76-81 GHz band

10

0 0

2

4

6

8

10 range (m)

12

14

16

18

20

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True Repeatability • Two different measurements on the same dummy • The extremely high repeatability proves the accuracy and stability of the whole setup (turntable, mounting of the dummy on the platform, network analyzer)

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System performance – Repeatability

Measurement 1: Dummy vFSS Adult on Aug 17th Measurement 2: Dummy vFSS Adult on Aug 20th

Good repeatability 10

List of dummies

KIT Dummy “Chantal” 4a Dummy Audi Dummy bicycle with cyclist vFSS Dummy adult vFSS Dummy child NHTSA Dummy adult NHTSA Dummy child TRL/innovITS Advance Dummy adult TRL/innovITS Advance Dummy child IDIADA Dummy IIHS Dummy 11 dummies from 8 providers tested 11

Results – RCS versus antenna height

Adult : RCS increases

Child : RCS decreases

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Results – RCS versus azimuth

Square profile !

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Results – Clothing effect

RCS vs Clothes 76-81 GHz

RCS vs Clothes 23-28 GHz

0

0 Adullt#1 Adult#2

-2

-2

-3

-3

-4

-4

-5 -6

-5 -6

-7

-7

-8

-8

-9

-9

-10

-10 Shirt

PVC rain coat

Polyester rain coat

W inter coat

Adult#1 Adult#2

-1

RCS (dBsm)

RCS (dBsm)

-1

Shirt

PVC rain coat

Polyster rain coat

W inter coat

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RCS Dummies / Humans Tentative of comparison of the RCS of dummies to humans

5

RCS (dBsm)

0

-5

-10

Average RCS in 76-81 GHz

Average RCS in 23-28 GHz

10 Child dummie s Adult dummie s Adult humans

5

Child dummies Adult dummies Adult dummies

0 RCS (dBsm)

10

-5

-10

-15 -15

-20 -20

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Conclusions • • • • • • • •

Successful RCS measurement campaign during 3 weeks at Ispra 100 measurements performed on 10 dummies and 5 volonteers Two microwave bands measured simultanously Good measurement repeatability Effect of clothing not very significant Effect of height investigated Qualitative comparison of dummies/humans Need to define a metric for quantitative comparison

Detailed results available at: http://sta.jrc.ec.europa.eu/emsl/EMSLdata/RCS-HumansDummies-Ispra-Aug2012.zip encrypted zip file with password: ‘ispra’

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