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Quadrature Amplitude Modulation for Acoustic Data Communication in Ultrasonic Structural Health Monitoring Systems


 Delivering information from the transducers to the base station is one of the main challenges in current guided wave-based structural health monitoring (SHM) systems. In recent years, novel solutions started to be investigated, which are based on guided ultrasonic waves (GWs). These waves experience mild power dissipation, hence being capable to travel comparatively long distances. The key idea is to exploit GWs as a means to transmit digital information (e.g. a damage indicator) directly over the mechanical waveguide. The advantage is that conventional radio-frequency communication is not needed and this is of the uttermost importance in harsh environments.
 Among the very different modulation techniques, a Quadrature Amplitude Modulation (QAM)–based modulation strategy is specifically employed in this work and numerical results are presented. More in detail, finite element simulations based on frequency steerable acoustic transducers (FSAT) are performed showing spatial multiplexing capabilities as widely used in modern 5G data communication systems.