A low cost A low cost approach to acoustic lters acting as GPR …jmfriedt.free.fr/slides_iwagpr2015.pdf · 2015. 7. 15. · A. Glinsky, Theremin: Ether Music And Espionage, Uni-versity

A low costapproach to

acoustic filtersacting as GPR

cooperativetargets for

passive sensing

J.-M Friedt & al.jmfriedt@femto-

st.fr

What are RADARcooperativetargets ?

Why GPRcooperativetargets ?

Radiofrequencyacoustictransducers ascooperativetargets

Softwareoptimization fordual sub-surfaceand sensormonitoring

Low costdemonstrationusing off-the shelfradiofrequencyfilters

Conclusion andperspectives

A low cost approach to acoustic filters acting asGPR cooperative targets for passive sensing

J.-M Friedt & A. Hugeat

FEMTO-ST Time & Frequency, Besançon, FranceContact: [email protected]

References and slides at http://jmfriedt.free.fr

July 8, 2015

IWAGPR2015 – Firenze, Italy

http://jmfriedt.free.fr




passive sensing


st.fr







Outline

• What are RADAR cooperative targets ?• Why GPR cooperative targets ?• Radiofrequency acoustic transducers as cooperative targets• Software optimization for dual sub-surface and sensor monitoring• Low cost demonstration using off-the shelf radiofrequency filters





passive sensing


st.fr







What are RADAR cooperativetargets ?

1 target whose backscattered signal isrepresentative of its state (identification,measurement)

2 active targets: radar beacons (racon), IFF

3 passive targets: buried dielectric reflectors

4 this work: use of radiofrequency transducersbased on surface acoustic wave propagation(RF filters)

H. Stockman, Communication by means of reflected powerProc. IRE 36 (Oct. 1948) pp.1196–1204(picture from http://geogdata.csun.edu/~aether/pdf/volume_05a/rosol.pdf)


http://geogdata.csun.edu/~aether/pdf/volume_05a/rosol.pdf




passive sensing


st.fr












A. Glinsky, Theremin: Ether Music And Espionage, Uni-versity of Illinois Press (2005)

http://madmikesamerica.com/2010/08/the-thing-and-the-curious-life-of-leon-theremin/thing2/





passive sensing


st.fr












A. Glinsky, Theremin: Ether Music And Espionage, Uni-versity of Illinois Press (2005)





passive sensing


st.fr












D. J. Thomson, D. Card, and G. E. Bridges, RF CavityPassive Wireless Sensors With Time-Domain Gating-BasedInterrogation for SHM of Civil Structures, IEEE SensorsJournal . 9 (11) (Nov. 2009), pp.1430-1438





passive sensing


st.fr












C.T. Allen, S. Kun, R.G Plumb, The use of ground-penetrating radar with a cooperative target, IEEE Trans-actions on Geoscience and Remote Sensing, 36 (5) (Sept.1998) pp. 1821– 1825





passive sensing


st.fr







Why GPR cooperative targets ?

• Complement buried structure information with physical quantitymeasurement

• Accessible quantities: temperature, stress (pressure), identifier (ID)• Measurement range: depends on RADAR cross section – typical

losses in the 30-40 dB range

Passive cooperative target (no local battery source) for extended lifeexpectancy (limited by packaging)

Envisioned applications:

• pipe tagging/stress/temperature• soil moisture 1

• concrete temperature 2

1L. Reindl & al., Radio-requestable passive SAW water-content sensor, IEEETrans. Microwave Theory & Techniques, 49 (4), (Apr. 2001), pp. 803–808

2J. Kim, R. Luis, M.S. Smith, J.A. Figueroa, D.C. Malocha, B.H. Nam, Concretetemperature monitoring using passive wireless surface acoustic wave sensor systemSensors and Actuators A 224 (Febr. 2015), pp.131–139





passive sensing


st.fr







SAW basicsDemonstrated with dedicated readers for Surface Acoustic Wave (SAW)transducers (Transense, CTR, Sengenuity, RSSI, SenSanna, Frec|n|sys, SENSeOR).

M1

M2

M3

IDT

typical dimensions:10 mm x 4 mm

@ 100 MHz

• Sensor: φ = 2π · D/λ = 2πD · f /c with dc/c(T , σ) known• GPR is wideband pulse generator ⇒ delay line architecture.• This work aims at providing GPR-compatible SAW sensors ...• ... or divert existing SAW filters for sensing purpose.





passive sensing


st.fr







Radiofrequency acoustic (SAW)transducers as cooperative targets

• from a user perspective, an electrical dipole• physics: conversion of incoming RADAR pulse

to an acoustic (mechanical) wave throughinverse piezoelectric effect

• acoustic wave propagates on the surface of thepiezoelectric substrate at a speed of3000-5000 m/s

• the acoustic wave is reflected by patternedmirrors, reaches the transducer and isconverted back to an electromagnetic pulse(RADAR echo) ⇒ tag or sensor

Piezoelectricity is linear process: returned power isa fraction of incoming power, no threshold

Unlike RFID which requires power while being operated, SAW transducers are ideally

suited for GPR interrogation





passive sensing


st.fr







Software optimization for dualsub-surface and sensor monitoring

• Separate sensor response fromsubsurface reflectors by delaying echobeyond any possible interfacereflection (2 µs = 4 mm long sensor at4000 m/s)

• Short term response = buriedstructures (“clutter”)

• Long term response = buried sensor

Available GPR only allows for a small num-ber of samples (




passive sensing


st.fr











Solution: define two time windows, one fo-cusing on the subsurface structures (e.g. 0-200 ns) and another on the sensor (e.g.1000-1200 ns)





passive sensing


st.fr











Only software re-design, hardware re-mains the same (reconfigure start delay ofthe stroboscopic measurement)

⇒ demonstrated on Mal̊a ProEx GPRhttps://sourceforge.net/projects/proexgprcontrol/


https://sourceforge.net/projects/proexgprcontrol/




passive sensing


st.fr







Low cost demonstration usingoff-the shelf radiofrequency filters

• Dedicated transducers require cleanroom fabrication capability ableto handle piezoelectric substrates

• Design considerations:• transducer transfer function must match GPR pulse spectrum• delay must be within measurement range of GPR• reflective transducer operation (most filters operate in transmission)

Measurement example, using an TDK/Epcos B3607 filter:

-8

-7

-6

-5

-4

-3

-2

-1

0

100 120 140 160 180 200 220 240 260

|S11| (

dB

)

frequency (MHz)

0

0.005

0.01

0.015

0.02

0.025

0.03

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

retu

rned

pow

er (

a.u.)

time (us)IWAGPR2015 – Firenze, Italy




passive sensing


st.fr











-8

-7

-6

-5

-4

-3

-2

-1

0

100 120 140 160 180 200 220 240 260

|S11| (

dB

)

frequency (MHz)

0

0.005

0.01

0.015

0.02

0.025

0.03

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

retu

rned

pow

er (

a.u.)

time (us)

power supply(heater)

resistance

TX

RX

Pt100 probe

monitoring

100 MHz

unshielded

antennas

SAW

sensor





passive sensing


st.fr











0 100 200 300 400 500 600 700 800

trace number (a.u.)

2.75

2.8

2.85

2.9

2.95

3

time (us)

-5

0

5

10

15

0 100 200 300 400 500 600 700 800u

nw

rap

ped

ph

ase

(rad

)time (s)

25

30

35

40

45

50

0 100 200 300 400 500 600 700 800

tem

per

atu

re (

deg

C)

time (s)





passive sensing


st.fr







Signal processing stepsConverting the echo delays to a meaningful measurement:

1 multiple echoes from the sensor to get rid of RADAR-targetdistance dependence

2 phase measurement of each returned echo: cross-correlation

3 for single echo (eg SAW filter):phase of the Fourier transformof the main spectrumcomponent (assuming constantRADAR-target distance)

4 SAW delay lines will usually bemore narrowband than RADARpulse ⇒ long echo⇒ improved SNR

5 sub-sampling period resolution:polynomial fit of the cross-correlation maximum

6 danger: multiple nearby cross-correlation peaks ⇒ risk of 2πrotation: ϕ = 2πD/λ = 2πD · f /c ⇒ dϕT = −2πDf /c · dcT/cwhere dcT/c(LiNbO3) = 60 ppm/K. If D = 1 cm, 2π phase rotationon LiNbO3/128 for 35 K at 100 MHz (cLNO128 ' 4000 m/s).





passive sensing


st.fr







Signal processing stepsConverting the echo delays to a meaningful measurement:

1 multiple echoes from the sensor to get rid of RADAR-targetdistance dependence

2 phase measurement of each returned echo: cross-correlation3 for single echo (eg SAW filter):

phase of the Fourier transformof the main spectrumcomponent (assuming constantRADAR-target distance)

4 SAW delay lines will usually bemore narrowband than RADARpulse ⇒ long echo⇒ improved SNR

5 sub-sampling period resolution:polynomial fit of the cross-correlation maximum

6 danger: multiple nearby cross-correlation peaks ⇒ risk of 2πrotation: ϕ = 2πD/λ = 2πD · f /c ⇒ dϕT = −2πDf /c · dcT/cwhere dcT/c(LiNbO3) = 60 ppm/K. If D = 1 cm, 2π phase rotationon LiNbO3/128 for 35 K at 100 MHz (cLNO128 ' 4000 m/s).

-10

-5

0

5

10

0 20000 40000 60000 80000 100000

phase (rad)

time (s)

72 ns232 ns

20

30

40

50

60

70

80

90

100

0 20000 40000 60000 80000 100000

temp. (degC)

time (s)

time difference

2450 MHz LiNbO3/128 device





passive sensing


st.fr







Conclusion and perspectives• Extend the range of applications of (Ground Penetrating) RADAR

by monitoring physical quantities• Use existing instruments for probing cooperative targets 3• Acoustic transducers provide a compact solution ...• ... ideally suited to GPR interrogation.• Software enhancement dedicated

to sensor monitoringPerspectives:

• software improvement for real timedisplay of the sensor visibility andphysical quantity value (calibration)

• beyond physical quantity: chemicalcompound detection (dedicated sensordesign)

Acknowledgement: TDK/Epcos kindly provided sam-

ples of the B39111B5232H310 and B39191B5087H810

filters, with support of S. Ballandras (Frec|n|sys).3J.-M Friedt, A. Saintenoy & al, High-overtone Bulk Acoustic Resonators as

passive Ground Penetrating Radar cooperative targets, J. Appl. Phys 113 (13), 2013IWAGPR2015 – Firenze, Italy

What are RADAR cooperative targets ?Why GPR cooperative targets ?Radiofrequency acoustic transducers as cooperative targetsSoftware optimization for dual sub-surface and sensor monitoringLow cost demonstration using off-the shelf radiofrequency filtersConclusion and perspectives

Documents

A low cost A low cost approach to acoustic lters acting as GPR …jmfriedt.free.fr/slides_iwagpr2015.pdf · 2015. 7. 15. · A. Glinsky, Theremin: Ether Music And Espionage, Uni-versity