Equalization of ultrasonic transducers based on evolutionary algorithm and IIR lattice filter

In ultrasonic non-destructive evaluation (NDE) application, band-pass ultrasonic transducer is recognized as a main factor degrading the time fidelity of inspection. Due to low computational complexity and simplicity, finite impulse response (FIR) equalizer techniques have been applied to undo the band-pass response of the narrowband ultrasonic transducers in our previous work. Compared to FIR filters, infinite impulse response (IIR) structures exhibit considerable advantages including the potential reduction of computational complexity and the increased accuracy with equivalent order. However, the application of the IIR filters is seriously hindered by their drawbacks such as the multimodal performance surface and stability issue. Aiming to mitigate the limitations posed by the IIR filters, this paper introduces an evolutionary algorithm-based IIR filter implemented as the lattice structure which greatly simplifies the stability control and then applies it in the physical ultrasonic transducer equalization. The experimental results on numerical data as well as the practical ultrasonic NDE signals are provided to demonstrate the effectiveness of the proposed method. © 2008 Elsevier Ltd. All rights reserved.