Increasing the acquisition speed of a multi-channel guided wave system via simultaneous coded excitations

Many guided wave systems that are being evaluated for nondestructive evaluation or structural health monitoring utilize multiple transducers. Data are typically acquired by exciting each transducer in turn and recording received signals on the remaining transducers either simultaneously or separately. For either case, it can be very slow to acquire data because of the multiple transmission cycles combined with a slow repetition rate and extensive signal averaging. This long acquisition time brings another disadvantage by increasing the risk of environmental changes occurring during the complete acquisition process. For example, applied loads and temperature could change over the several seconds that are frequently required to acquire data. To increase the acquisition speed, it is proposed here to simultaneously trigger multiple transmitters, and each transmitter is driven with a unique, coded excitation. The simultaneously transmitted waves are captured by one or more receivers, and their responses are processed by dispersive matched filtering to separately extract the contribution from each transmitter. Results are shown for signals obtained from a spatially distribution array mounted on an aluminum plate.