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PPM-EMAT Design Configurations for Ultrasonic Communication through Metallic Channel

Electromagnetic acoustic transducers (EMATs) are a preferable non-contact alternative to PZT transducers. EMATs use the electromagnetic method to transform electrical energy into ultrasonic energy. Ultrasonic waves are generated in the material regardless of the contact condition with the channel surface, which overcomes signal uncertainty faced by the coupling conditions of PZT transducers. We have investigated the feasibility of using periodic-permanent-magnet electromagnetic acoustic transducers (PPM-EMATs) as transmitters and receivers for ultrasonic communication. By configuring the winding structure of coils, the periodicity of the permanent magnet array, and directions of polarizations, the PPM - EMA Ts are designed to generate shear horizontal (SH) waves through the plate channels and torsional waves through the pipe channels. Furthermore, the ultrasonic wave reflections are proved to be the main reverberations causing the multipath effect. Experimental tests of signal transmission with PPM-EMAT on a 160cm-long stainless-steel plate determine the optimal frequency for communication to be 700KHz. Information transmission experimental results confirm the validity of PPM-EMAT for communication with a bitrate of 10 kbps.