Caratterizzazione della RCS di Pedoni nelle Bande GHz e GHz
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 Sec...
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
RCS Dummies / Humans Tentative of comparison of the RCS of dummies to humans
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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
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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’