RADAR cooperative target

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transducers as Ground Penetrating

RADAR cooperative

targets for sensing applications J.-M Friedt & al.

Cooperative target design Experimental demonstration Timebase stability issue Dedicated hardware for sensor

Acoustic wave transducers as Ground Penetrating RADAR cooperative targets for

sensing applications

J.M Friedt^1,2, D. Rabus³, G. Martin¹, G. Goavec-M´erou^1,3, F. Ch´erioux ¹, M. Sato²

1FEMTO-ST Time & Frequency department, Besan¸con, France

2 CNEAS, Tohoku University, Sendai, Japan

3SENSeOR SAS. Besan¸con, France jmfriedt@femto-st.fr

slides and references atjmfriedt.free.fr

October 5, 2017

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RADAR cooperative

RADAR cooperative target

• apassivetarget is illuminated by an electromagnetic wave,

• this target is designed so that the backscattered signal is representative of ameasurement,

• the sensor is separated from clutter usingTime Division Multiple Access(delay the sensor response beyond clutter)

• the sensor response is preferably included in atime/phase

information rather than an amplitude, sensitive to too many effects.

[1] C.T. Allen, S. Kun, R.G Plumb, The use of ground-penetrating radar with a cooperative target, IEEE Transactions on Geoscience and Remote Sensing,36(5) (Sept.

1998) pp. 1821– 1825

[2] D. J. Thomson, D. Card, and G. E. Bridges, RF Cavity Pas- sive Wireless Sensors With Time- Domain Gating-Based Interroga- tion for SHM of Civil Structures, IEEE Sensors Journal9(11) (Nov.

2009), pp.1430-1438

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RADAR cooperative

Acoustic transducers

• Acoustic =mechanical wavepropagating insolidmedia (no relation to sound/seismics)

• Surface acoustic wave transducer: use apiezoelectric substrateto convert an electromagnetic wave to acoustic wave

• Classical analog radiofrequency processing circuit (seen as an electrical dipole by the user)

• the acoustic wave is10⁵ slowerthan the electromagnetic wave

• λ=c/f: shrinkc⇒shrinkλ⇒compact sensors

• Cleanroom processing since 1 m wavelength at 300 MHz

→10µm wavelength.

• At 2.45 GHz,λ= 1.2 µm or 300 nm wide electrodes !

• Piezoelectric substrate is anisotropic: select crystal orientation tomaximize sensor sensitivity (stress, temperature, pressure, chemical sensing)

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RADAR cooperative

Acoustic transducers as RADAR cooperative targets

Two ways of delaying sensor signal beyond clutter:

• delay pathlong enough (1µs=100 m-long coaxial cable but 1 mm long acoustic path)

• resonatorstores energy and slowly releases it with a time constant Q/(πf)

• initial returned signal level given by theelectro- mechanical coupling coefficient of the piezo substrate

• accurate time delay asphasemeasurement using cross-correlation

0 0.5 1 1.5 2

−100

−80

−60

−40

−20 0

time (us)

loss (dB)

resonator, =7 us resonator, =0.7 us FSPL ~ 1/d^4

−8.6 dB/τ delay line high Q, low K^2

resonator,

receiver noise level

low Q, high K^2 resonator,

sensor measurement τ τ FSPL

clutter

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RADAR cooperative

Experimental demonstration:

chemical sensing

• Coat the propagation path with a layer absorbing the compound to be detected

• c=p

E/ρwithE the elastic constant and ρthe density:

• load mass⇒ρ↑⇒c↓

• stiffen the layer⇒E ↑⇒c ↑

• basic principle of the so called Quartz Crystal Microbalance

0 500 1000 1500 2000

-200 -150 -100 -50 0 50

time (s)

phase (deg)

H2S H2O

6 mm

Sub-surface hydrogen sulfide detection using custom GPR¹

1F. Minary, D. Rabus, G. Martin, J.-M. Friedt,Note: a dual-chip stroboscopic pulsed RADAR for probing passive sensorsRev. Sci. Instrum.87, p.096104 (2016) ^{5 / 14}

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RADAR cooperative

Sandbox experiment

Antenna radiation pattern characterization and interrogation range

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RADAR cooperative

Returned signal with

depth/position

^Y

X Z

Left: returned signal as a function of depthZ ⇒1 m range

-500 -450 -400 -350 -300 -250 -200 -150

0 0.2 0.4 0.6 0.8 1

returned signal (a.u)

time (us)

35 cm 48 cm 61 cm 75 cm 88 cm 103 cm

50 100 150 100 50 0

0

0.2

0.4

0.6

0.8

position (cm) echo 1

echo 2

time (us)

-550 -500 -450

Right: returned signal as a function of position⊥to dipole axis (X)

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RADAR cooperative

Sandbox experiment

_Y

X Z

Returned echoes as a function of the position of the sensor along the pipe (Y), moving in a direction parallel to the length of the dipole.

61 cm

0 0.5 1 1.5 2 2.5 3

0

0.2

0.4

0.6

0.8

1

position (m)

time (us)

-620 -600 -580 -560 -540 -520 -500 -480

103 cm

0 0.5 1 1.5 2 2.5 3

0

0.2

0.4

0.6

0.8

1

position (m)

time (us)

-620 -600 -580 -560 -540 -520 -500 -480

61 cm in gravel 103 cm in gravel

⇒50^◦ angular aperture along the dipole direction and 70^◦⊥to dipole axis.

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RADAR cooperative

Timebase stability issues

Mal˚a ProEx v.s homemade impulse GPR v.s iFFT(network analyzer) ?

0 500 1000 1500 2000

0 1 2 3 4 5

time (s)

delay (ns)

std()=34 ps=1.6 K=320 ng/cm2

27 pF Vishay NPO frequency synthesizer

• Challenge of homemade GPR: avalanche transistor pulse generator design

• Challenge of network analyzer: time-gating for isolation

Targetedstability: 70 ppm/K for a delay difference of 0.3µs requires 21 ps stability for 1 K resolution

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RADAR cooperative

Timebase stability issues

0 1000 2000 3000 4000 5000 6000 0

1 2 3 4 5

trace number (s)

delay (ns)

std=213 ps std<16>=100 ps

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RADAR cooperative

Timebase stability issues

0 2000 4000 6000 8000

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2

trace number (s)

delay (ns)

std=21.6 ps

freezing spray x2 freezing spray

0 10 20 30 40 50

-5 0 5 10

collector voltage (V)

time (ns)

8 7 6 5 4 3 2 1

High voltage (200 V) trig

antenna

C R

Temperature measurement Avalanche transistor pulse

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RADAR cooperative

434 MHz resonator measurement in concrete

Dedicated frequency stepped resonator measurement electronics for a dedicated temperature sensor.

Experimental setup

25 30 35 40 45

0 2 4 6 8 10 12 14

temperature (degC)

1.45 1.46 1.47 1.48 1.491.5 1.51 1.52

0 2 4 6 8 10 12 14

freq. difference (MHz)

-25 -20 -15 -10-50 5 10

0 2 4 6 8 10 12 14

emitted power (dBm)

time (hours)

0 50 100 150 200

0 5 10 15 20 25 30

temperature (degC)

1.151.11.2 1.251.3 1.351.4 1.451.5

0 5 10 15 20 25 30

freq. difference (MHz)

-25 -20 -15 -10 -5 0 5

0 5 10 15 20 25 30

emitted power (dBm)

time (hours)

Curing Heating at 160^◦C

Assess penetration depth of a 400 MHz antenna Mal˚a probing sensors ? 12 / 14

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RADAR cooperative

Conclusion

• Development ofpassivecooperative target forwirelesssensing in civil engineering structures and buried environments (e.g. pipes).

• Acoustic (≤2.4 GHz) and dielectric (10-24 GHz) resonator or relay line demonstrated ascooperative targets for sensingapplications

• Systemsapproach: link budget from GPR emitter, to sub-surface antenna, to transducer and back to receiver.

But practical implementation remains to be demonstrated:

• Practical implementation in a useful scenario ? impact of rebars ?

• Use of commercial GPR, dedicated GPR or dedicated cooperative target reader ?

• Impact of strong radiofrequency emission regulations in Japan ?

A strong team of possible partners exists on both sides to achieve this goal (Pr.

Hashimoto in Chiba², Pr. Yamanaka³⁴ and Pr. Esashi⁵in Sendai, Pr. Kondoh in Shizuoka University).

2www.te.chiba-u.jp/~ken/

3www.material.tohoku.ac.jp/~hyoka/BallSAW-H2sensor2003IEEEus.pdf

4www.tohoku.ac.jp/en/news/university_news/falling_walls_venture_

sendai_2017_1.html

5J.H. Kuypers, L.M. Reindl, S. Tanaka S, M. Esashi,Maximum accuracy evaluation scheme for wireless saw delay-line sensors, IEEE Trans. Ultrason.

Ferroelectr. Freq. Control. 55(7):1640-52 (2008) ^{13 / 14}

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RADAR cooperative

Conclusion

• Development ofpassivecooperative target forwirelesssensing in civil engineering structures and buried environments (e.g. pipes).

• Acoustic (≤2.4 GHz) and dielectric (10-24 GHz) resonator or relay line demonstrated ascooperative targets for sensingapplications

• Systemsapproach: link budget from GPR emitter, to sub-surface antenna, to transducer and back to receiver.

But practical implementation remains to be demonstrated:

• Practical implementation in a useful scenario ? impact of rebars ?

• Use of commercial GPR, dedicated GPR or dedicated cooperative target reader ?

• Impact of strong radiofrequency emission regulations in Japan ?

A strong team of possible partners exists on both sides to achieve this goal (Pr.

Hashimoto in Chiba , Pr. Yamanaka and Pr. Esashi in Sendai, Pr. Kondoh in Shizuoka University).

Manuscript: http://jmfriedt.free.fr/fr_jp_ws2017.pdf

Slides: http://jmfriedt.free.fr/171005.pdf

Additional informations: http://jmfriedt.free.fr/

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