Time Reversal Signal Processing for Ultrasonic Communication through Metal Channels

Achieving a high bitrate (BR) and low bit error rate (BER) in ultrasonic communication through solids are challenging due to bit-wavelet spreading caused by the channel dispersion, attenuation, and multipath effect. This undesirable effect is more pronounced particularly in irregular shape channels like an elbow pipe and bent or warped plates. Time-reversal (TR) signal processing is a promising technique which can compress the spreading of the bit-wavelet and concentrate the signal energy for improving the communication BR. In this study, we examined the performance of the TR technique applied to the elbow shape pipe channel using piezoelectric transducers (PZT) and steel plate channel using electromagnetic acoustic transducers (EMATs). This paper presents an overview of the system design of the TR processing for ultrasonic communication. By comparing the signal- to-noise ratio (SNR) of different pulse duration for generating the TR signal, we determined the optimal pulse duration to be used as one-bit information. An experimental model is used to demonstrate the performance of TR method for ultrasonic communication through complex metal channels. Furthermore, results show the pulse-position modulation (PPM) is highly effective for improving BER in complex channels with severe dispersion, attenuation, and multipath effects.