Ultrasonic Communication System Design Using Electromagnetic Acoustic Transducer

摘要

Ultrasonic communication is a technique of transmitting a message through solids such as steel plates or pipes. Electromagnetic acoustic transducers (EMATs) are non-contact sensors able to generate and receive ultrasonic waves. In this study, periodic-permanent-magnet (PPM) EMATs are used to produce shear-horizontal (SH) waves. We present experimental results to show channel characterization of SH waves carrying information over the frequency range of 200 kHz to 800 kHz. An experimental ultrasonic communication platform was built for assessing the SH wave propagation through stainless steel plate channels. An arbitrary function generator (AFG) and a power amplifier with 50 dB gain excite PPM-EMAT resulting different SH modes. The transmitted ultrasonic signal is detected by the SH-wave EMAT receiver. The received signal is conditioned, amplified and sampled by a digital oscilloscope. The AFG and the digital oscilloscope can be configured by the computer. In addition, the receiver is connected to an impedance matching network for signal conditioning which minimizes the signal interference and reflections. A random binary message is modulated with amplitude shift keying (ASK) also known as on-off keying (OOK), and the received message is processed to recover the binary code to examine bit error rate (BER). The proposed method can transmit digital data through a 165 cm distance in the presence of undesirable multipath effect with the bit rates of 2.5 kbps under 0.48% BER.