Separation of Signals Acquired with EMAT in Dual Coil Configuration
Václav Matz, Czech Republic · 2008
In this paper, the proposal of electromagnetic acoustic transducer (EMAT) in dual coil configuration with consequent application of signal de-noising algorithm is presented in detail. Dual EMAT contains two operated coils in a single housing. Both coils transmit and receive the ultrasonic signal. Based on the proposed coil configuration, two signals characterizing material structure at the same place are received and consequently evaluated. This configuration makes the flaw detection process more accurate and the noise level can be efficiently suppressed using advanced signal processing algorithms. In this study, we also investigate the proposal of signal processing algorithm used for signal and noise separation. The proposed algorithm based on independent component analysis (ICA) uses the statistical information to separate useful signal as fault echo from the undesirable echoes that are caused by the scattering from grains contained in materials. Using our proposed algorithm it is possible to recognize the fault echo that is hidden under the noise level from backscattering noise. The performance of both, proposed EMAT in dual coil configuration and algorithm is compared on simulated and acquired EMAT signals.