19 th World Conference on Non-Destructive Testing 2016 1 License: http://creativecommons.org/licenses/by-nd/3.0/ Transducer-to-Transducer Communication in Guided Wave Based Structural Health Monitoring Jochen MOLL 1 , Luca DE MARCHI 2 , Alessandro MARZANI 2 1 Goethe Universität Frankfurt am Main, Department of Physics, Frankfurt, Germany 2 University of Bologna, Bologna, Italy Contact e-mail: moll@physik.uni-frankfurt.de; l.demarchi@unibo.it; alessandro.marzani@unibo.it Abstract. Systems for guided wave (GW) based structural health monitoring are limited in the frequency bandwidth of the excitation signal due to the underlying wave’s dispersion that causes a broadening of the waveform along the waveguide. Hence, bandlimited waveforms such as toneburst or chirp signals are widely employed. Recently, the authors have investigated the potential of phase-modulated signals, known from CDMA-communication systems, as a possible way to overcome such limitation. It was found that this class of excitation enables a parallel transmission and reception of all piezoelectric transducers which may lead to a significant reduction in the overall system complexity, because channel switching is not required anymore. In addition, the signal-to-noise ratio of the measured signal can be improved by considering phase modulation signals of longer code length. In this paper, we investigate phase-modulated signals in terms of their capability to transmit digital information on the health status of the structure through the structure itself. This may lead to autonomous GW-based SHM systems where the sensor nodes do not communicate with each other using radio frequency (RF) communication, but where the information are being delivered through the mechanical waveguide. A proof-of-concept will be demonstrated here on an isotropic plate using a Monte Carlo simulation. The implementation of the concept requires to compensate the guided wave signals from dispersion. Therefore, a suitable phase compensation designed on the group velocity of the GW-modes, is applied. Such transformation has two beneficial effects: 1) it compensates for the detrimental effect of dispersion, 2) it preserves the pseudo-orthogonality of the encoded pulses, because it is computed with a unitary operator. Introduction Data communication over acoustic waveguides has been employed in a variety of applications in which standard radio frequency (RF) or optical communication cannot be used or expenses are too high. The first example is an underwater telephone developed by the Naval Underwater Sound Laboratory in 1945 [1]. Since then several systems for underwater communication based on compressional waves have been demonstrated. One example is borehole communication where acoustic waves are sent across the drill string [2]. An orthogonal frequency-division multiplexing (OFDM)-scheme for acoustic telemetry is demonstrated in [3]. Similarly, long distance links for wireless communication of 40 m and 70 m in water-filled pipes are shown in [4]. More info about this article: http://ndt.net/?id=19435