Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Novel narrowband acoustic sensors for sub-GHzISM compliant wireless measurements

D. Rabus 1, T. Barron 1, E. Lebrasseur 1, S. Alzuaga 1, G. Martin 1,J.-M Friedt 2, S. Ballandras 1,2

1 FEMTO-ST Time & frequency dpt., UMR 6174 CNRS, Besancon, France2 SENSeOR SAS, Besancon, France

Contact: {jmfriedt,ballandr}@femto-st.frslides available at http://jmfriedt.free.fr

October 29, 2011

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

High-overtone Bulk AcousticResonator (HBAR): basics

Objective: robust structure for high frequency/high Q resonators

Mechanical structure: stack of single-crystal piezoelectric layer + lowacoustic loss substrate ⇒ robust structure (� FBAR) while reachinghigh frequency (thin piezo layer)

Issues:

• thin single-crystal piezoelectric layer 1

• wafer scale assembly, 2

• low acoustic loss adhesion strategy,

• reaching the buried electrode

1T. Baron, D. Gachon, G. Martin, S. Alzuaga, D. Hermelin, J.-P. Romand, S.Ballandras, Temperature Compensated Radio-Frequency Harmonic Bulk AcousticResonators, Proceedings of IEEE International Frequency Control Symposium (2010)

2T. Baron, D. Gachon, J.-P. Romand, S. Alzuaga, S. Ballandras, J. Masson, L.Catherinot, M. Chatras, A Pressure Sensor Based on a HBAR MicromachinedStructure, Proceedings of IEEE International Frequency Control Symposium (2010)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

High-overtone Bulk AcousticResonator (HBAR): expected

responseCoupled resonators between the thin piezoelectric film and low acousticloss (thick) substrate

0

0.2

0.4

0.6

0.8

1

0 200 400 600 800 1000

Y (

a.u

.)

frequency (MHz)

MATERIAL 1

Adhesion layer

Electrode

(low acoustic

losses)

MATERIAL 2

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

High-overtone Bulk AcousticResonator (HBAR): expected

responseCoupled resonators between the thin piezoelectric film and low acousticloss (thick) substrate

0

0.2

0.4

0.6

0.8

1

0 200 400 600 800 1000

Y (

a.u

.)

frequency (MHz)

e

f=n.V/(2.e)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Manufacturing flowchart

piezoelectric

material

low acoustic

loss material

Au

grinding &

polishing

low acoustic

loss material

Au

piezoelectric

electrode

patterning

low acoustic

loss material

Au

piezoelectric

1 4” wafer scale process

2 room temperature gold-eutectic bonding (high pressure)

3 if no access to buried electrode, coupled resonators

4 small resulting dimension (<1 mm×1 mm)

5 bulk electrode ⇒ reduced aging and influence of environment (w.r.tIDTs)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Interrogation strategies• Closed loop (oscillator) is challenging due to the multimode

response• Open-loop interrogation strategy suitable for this multimode

transducer• Fourier transform of a frequency comb is a series of time-domain

pulses ⇒ can be used either as a narrowband transducer (frequencydomain) or a wideband, multimode device (time domain)

0

500

1000

1500

2000

0 0.5 1 1.5 2 2.5 3

Y (

a.u.

)

time (us)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Frequency v.s physical quantity(sensor)

• Stack of single-crystal materials ⇒ accurate simulation of thermalbehaviour (expansion coefficients)⇒ design of either temperature compensated device or temperaturesensor (mixed matrix simulation)

• Interrogation range limited by resonator Q (energy storage) andreceiver detection limit (LNA & power detector noise)

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

100 200 300 400 500 600 700 800

imag

(Y)

(S/m

2)

freq (MHz)

0

2e+06

4e+06

6e+06

8e+06

1e+07

1.2e+07

1.4e+07

100 200 300 400 500 600 700 800

real

(Y)

(S/m

2)

temperature dependence as a function of overtone number static capacitance

(varying LNO (YXl/163o )/quartz thickness ratios)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Frequency v.s physical quantity(sensor)

• Stack of single-crystal materials ⇒ accurate simulation of thermalbehaviour (expansion coefficients)⇒ design of either temperature compensated device or temperaturesensor (mixed matrix simulation)

• Interrogation range limited by resonator Q (energy storage) andreceiver detection limit (LNA & power detector noise)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Wireless measurement (frequency)Measurement strategy: frequency sweep-monostatic RADARinterrogation

offset

& gain

PA

power

detector

AD9954 DDS

frequencysweep

434+/−1 MHz

434+/−1 MHzAD8302

duplexer

switchARM7

1MS/s ADCUART SPI

microcontroller

1 program frequency synthesizer (AD9954) at frequency f

2 send RF pulse for a duration longer than Q/(πf ) s (resonator load)

3 switch antenna from emission (synthesizer + power amplifier) to reception (lownoise amplifier + power detector)

4 record magnitude of returned signal (wideband power detector) within thefrequency interrogation range after a duration � Q/(πf ) (resonator energyrelease)

5 f → f + ∆f & repeat for all values of f in interrogation band 3 4

3J.-M Friedt, C. Droit, G. Martin & S. Ballandras, A wireless interrogation system exploiting narrowband acoustic resonator for

remote physical quantity measurement, Rev. Sci. Instrum. 81, 014701 (2010)4

C. Droit, G. Martin, S. Ballandras & J.-M Friedt, A frequency modulated wireless interrogation system exploiting narrowbandacoustic resonator for remote physical quantity measurement, Rev. Sci Instrum. 81 (5), 056103 (2010)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Wireless measurement (frequency)

Experimental setup: SENSeOR interrogation unit programmed to probe432-434 MHz range (128 frequency steps), 16 averages(' 120 ms/measurement)

wideband narrowband

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Wireless measurement (frequency)

Experimental setup: SENSeOR interrogation unit programmed to probe432-434 MHz range (128 frequency steps), 16 averages(' 120 ms/measurement)

Experimental setup selected resonanceat 431.92495 MHz

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Wireless measurement (frequency)

⇒ resulting signal is a curve of returned power as a function offrequency f , with maxima close to each resonance frequency

4.31905e+08

4.3191e+08

4.31915e+08

4.3192e+08

4.31925e+08

4.3193e+08

4.31935e+08

0 50 100 150 200 250 300 350 400 450

freq

uenc

y (H

z)

time (a.u.)

⇒ after removing measurements with excessive standard deviationamongst the 16 measurements (28% of the dataset, red): σf = 1800 Hz

(if 1.7 MHz bandwidth allows for 170 K temperature span, 10 kHz/K and

σf = 1800 Hz∼ σT = 0.2 K)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Wireless measurement example

Measurement example: one resonance frequency as a function oftemperature, for one temperature compensated HBAR (black) and onetemperature sensivite HBAR (sensor: green & blue): wireless,f ∈ [431− 343] MHz.

⇒ differential frequency measurement strategy available (reduces sensorand local oscillator aging drift + correlated noise sources)

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Wireless measurement (time)

• Wideband RF pulseilluminates dielectricinterfaces & theHBAR sensor,

• bistaticconfiguration,

• basebandmeasurement ⇒amplitude and phaseinformations,

• demonstration usingunmodifiedcommercial GroundPenetrating RADAR(GPR) :Mala RAMAC

at constant

wavelength

GPR operates

pulse

high voltage

dipole antenna dipole antenna

dielectric interface

as cooperative target

passive sensor acting

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Wireless measurement (time)• Resonance over a wide frequency range ⇒ the same HBAR is

compatible with multiple RADAR frequencies (in GPR: defined byantenna dimensions)

• here all reflections are from the same acoustic mode: a sensor willrequire different modes exhibiting different sensitivities with respectto the physical quantity under investigation

-2500

-2000

-1500

-1000

-500

0

500

0 5e-07 1e-06 1.5e-06 2e-06 2.5e-06

retu

rned

pow

er (

a.u.

)

time (s)

200 MHz antenna

-2500

-2000

-1500

-1000

-500

0

500

0 5e-07 1e-06 1.5e-06 2e-06 2.5e-06

retu

rned

pow

er (

a.u.

)

time (s)

100 MHz antenna

Left: the same HBAR probed

with a GPR equipped with 100

(top) and 200 MHz (bottom)

antennas

IEEE Sensors 2011

Novelnarrowband

acoustic sensorsfor sub-GHz ISM

compliantwireless

measurements

Ballandras & al.

HBAR basics

Manufacturing

Wirelessinterrogation

Conclusion

Conclusion• Wafer scale manufacturing process of high Q multimode resonators,

• used as passive sensors compatible with time domain (wideband) &frequency domain (narrowband) wireless interrogation,

• demonstrated interrogation range of ' 1 m using a frequency sweepmonostatic switched RADAR strategy, or 100 & 200 MHzcommercially available Ground Penetrating RADAR

• single crystal materials ⇒ detailed modelling (mixed matrix),including thermal behaviour,

• ability to select materials and cuts in order to achieve temperatureturnover within the measurement range (reference device) or hightemperature drift (sensor),

• tiny dimensions (<1 mm×1 mm)

Contact: ballandr@femto-st.frIEEE Sensors 2011