Research Papers

An Ultrasonic Through-Wall Communication (UTWC) System Model

[+] Author and Article Information
Sebastian Roa-Prada

Department of Mechatronics Engineering,
Universidad Autónoma de Bucaramanga,
Avenida 42 No. 48-11,
Bucaramanga, Santander, Colombia
e-mail: sroa@unab.edu.co

Henry A. Scarton

Life Fellow ASME
Department of Mechanical,
Aerospace & Nuclear Engineering,
Rensselaer Polytechnic Institute,
Troy, NY 12180
e-mail: scarton@rpi.edu

Gary J. Saulnier

e-mail: saulng@rpi.edu

David A. Shoudy

e-mail: dshoudy@gmail.com

Jonathan D. Ashdown

e-mail: ashdoj@rpi.edu
Department of Electrical,
Computer & Systems Engineering,
Rensselaer Polytechnic Institute Troy,
NY 12180

Pankaj K. Das

Electrical and Computer Engineering,
University of California,
La Jolla, CA 92093-0407
e-mail: das@ece.ucsd.edu

Andrew J. Gavens

Bechtel Marine Propulsion Corporation,
Schenectady, NY 12309
e-mail: andrew.gavens.contractor@unnpp.gov

1Corresponding author.

Contributed by the Noise Control and Acoustics Division of ASME for publication in the Journal of Vibration and Acoustics. Manuscript received May 2, 2011; final manuscript received July 5, 2012; published online February 4, 2013. Assoc. Editor: Lonny Thompson.

J. Vib. Acoust 135(1), 011004 (Feb 04, 2013) (12 pages) Paper No: VIB-11-1098; doi: 10.1115/1.4007565 History: Received May 02, 2011; Revised July 05, 2012

Ultrasonic waves at 1 MHz are used to send information across solid walls without the needs for through wall penetrations. A communication channel is established by attaching a set of three ultrasonic transducers to the wall. The first transducer transmits a continuous ultrasonic wave into the wall. The second transducer is mounted on the opposite side of the wall (inside) and operates as a receiver and signal modulator. The third transducer, the outside receiving transducer, is installed on the same side as the first transducer where it is exposed to the signal reflected from the blended interface of the inside wall and inside transducer. Inside sensor data is digitized and the bit state is used to vary in time the electrical load connected to the inside transducer, changing its acoustic impedance in accordance with each data bit. These impedance changes modulate the amplitude of the reflected ultrasonic signal. The modulated signal is detected at the outside receiving transducer, where it is then demodulated to recover the data. Additionally, some of the ultrasonic power received at the inside transducer is harvested to provide energy for the communication and sensor system on the inside. The entire system (ultrasonic, solid wall, and electronic) is modeled in the electrical domain by means of electro-mechanical analogies. This approach enables the concurrent simulation of the ultrasonic and electronic components. A model of the communication system is implemented in an electronic circuit simulation package, which assisted in the analysis and optimization of the communication channel. Good agreement was found between the modeled and experimental results.

Copyright © 2013 by ASME
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Fig. 1

Elements of the communication system: 1–outside transmit transducer; 2–inside receive transducer; 3–outside receive transducer; 4–wall; 5–external power supply; 6–inside electronics; 7–inside sensor; 8–outside electronics

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Fig. 2

Diagram of the experimental setup. Drawing is to scale.

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Fig. 3

Püttmer's version of Leach's model of a piezoelectric crystal oscillating in thickness mode [9]

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Fig. 4

Simulation setup of an air-backed crystal and its attached layers

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Fig. 5

Simulation setups for frequency response analysis. (a) Setup for measuring the power delivered by the transmit transducer to a load medium. (b) Setup for measuring the power delivered to the inside load.

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Fig. 6

Geometry used in the calculations of the acoustic field generated by the transmit transducer

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Fig. 7

Geometry used in the calculation of beam spreading attenuation. Drawing not to scale.

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Fig. 8

PSpice model of the communication system

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Fig. 9

PSpice model of the inside load

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Fig. 10

PSpice model for calculation of the reflected wave

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Fig. 11

Impedance magnitude versus frequency for the outside transmit transducer

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Fig. 12

Impedance magnitude versus frequency for the receive transducers

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Fig. 13

Power delivered to the wall as a function of frequency, for an excitation of 40 V p–p, using the model in Fig. 5(a)

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Fig. 14

Power delivered to the inside load as a function of frequency, for an excitation of 200 N p–p, using the model in Fig. 5(b)

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Fig. 15

Axial response of the displacement amplitude for the transducers used in this project compared to the far-field approximation in fluids

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Fig. 16

Simulation results generated in PSpice for the voltage measured at the terminals of the outside receive transducer. External excitation is a CW, 40 V p-p.

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Fig. 17

Experimental measurement at the terminals of the outside receive transducer

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Fig. 18

Power delivered to the inside transducer as a function of frequency and magnitude of the inside load, for a 40 V p-p excitation of the transmit transducer




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