Modeling, Design and Temperature Characterization of an Ultrasonic Through-Wall Communication System

• Main Author: Roa Prada, Sebastian
• Format: Dissertation
• Language: English
• Subjects: engineering, mechanical; physics, acoustics
• ISBN: 1267252189; 9781267252180

This dissertation deals with the modeling and design of an ultrasonic through-wall communication system (UTWC) that uses ultrasonic waves to convey data from one side of a metallic wall to the other side without physical penetrations, and its characterization at previously untested elevated temperatures.
Two UTWC system configurations are examined. In the first configuration, a communication channel is established by attaching three ultrasonic transducers to the wall. The first transducer injects a continuous ultrasonic wave into the wall. The second transducer is mounted on the opposite side of the wall and operates as a receiver and signal modulator. The third transducer is installed on the same side as the first transducer and receives the signal that is reflected from the receive transducer. The second configuration uses only the first two transducers of the previous configuration; however, in this configuration the transmit transducer serves also as a receiver of the modulated signal reflected from the inside transducer. In both configurations, a sensor on the inside provides analog data (e.g. temperature) that is then digitized. The digitized bits are used to vary the electrical load applied to the electrical terminals of the receive transducer, changing its acoustic impedance in accordance with either of the two data bits. Some of the acoustic power exciting the receive transducer is harvested to energize the communication electronics and sensor on the receive side. An equivalent electric circuit for the UTWC system is derived and simulated using the commercial package PSpice, which facilitates the analysis of the complete system.
The temperature characterization of the channel focuses on the study of the impact of elevated temperature, i.e., 315 °C (600 °F), on the performance of the UTWC system. A modified BSPT piezoelectric material has been selected as the transducer material for elevated temperature operation due to its relatively strong and stable piezoelectric activity at high temperature, and because of its commercial availability. Impedance measurements of two BSPT crystals were taken at different temperatures to infer the temperature dependence of the properties of this material, which enabled predicting changes in the performance of the UTWC system at varying temperatures.