Excitations and Signal Processing for Multiprobe Setups

The possibility of taking advantage of multiprobe setups for ultrasound non-destructive testing (NDT) is introduced with reference to its physical and signal processing aspects. Preliminarily, a major distinction is made between phased-arrays and actual multi-transducer configurations. Then, most of the chapter is devoted to the latter type of setup. In this framework, the previously introduced channel model developed for single-probe operation, is extended to setups featuring multiple transmitting transducers (TXs) and receiving transducers (RXs) meant to be employed simultaneously in a so-called multiple input, multiple output (MIMO) configuration. It is also illustrated how this configuration relates to multi-user communication networks. Proper merit factors suitable for characterizing the performances of multiprobe systems are presented by taking advantage of the probabilistic system view introduced for single-probe systems. Finally, various classes of signals that can be adopted in MIMO NDT systems are described. These excitations may be designed according to random or deterministic approaches. In better detail, special techniques based on tessellation of the time-frequency (TF) plane are developed to design excitation signals capable of joining assuring contextually the good degree of appropriateness for MIMO setups and the good signal-to-noise (SNR) and resolution properties of chirps.

[1]  Robert E. Milleit.  A Matched-Filter Pulse-Compression System Using a Nonlinear FM Waveform , 1970, IEEE Transactions on Aerospace and Electronic Systems.

[2]  Sergio Callegari.  Achievement of preassigned spectra in the synthesis of band-pass constant-envelope signals by rapidly hopping through discrete frequencies , 2014, 2014 IEEE International Symposium on Circuits and Systems (ISCAS).

[3]  G. Turin,et al.  An introduction to matched filters , 1960, IRE Trans. Inf. Theory.

[4]  Sergio Callegari,et al.  Spectral properties of chaos-based FM signals: theory and simulation results , 2003 .

[5]  F. Lam,et al.  Pulse compression techniques in ultrasonic non-destructive testing , 1976 .

[6]  Leon Cohen,et al.  Time Frequency Analysis: Theory and Applications , 1994 .

[7]  H. Ermert,et al.  Chirp signal matching and signal power optimization in pulse-echo mode ultrasonic nondestructive testing , 1994, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  E. S. Furgason,et al.  High-speed digital Golay code flaw detection system , 1983 .

[9]  Sergio Callegari,et al.  Constant envelope pseudo orthogonal excitations for ultrasound testing , 2013, 2013 18th International Conference on Digital Signal Processing (DSP).

[10]  Sergio Callegari,et al.  Exploiting Non-Linear Chirp and sparse deconvolution to enhance the performance of pulse-compression ultrasonic NDT , 2012, 2012 IEEE International Ultrasonics Symposium.

[11]  Helmut Bölcskei,et al.  An overview of MIMO communications - a key to gigabit wireless , 2004, Proceedings of the IEEE.

[12]  Sergio Callegari,et al.  Chaos-based FM signals: application and implementation issues , 2003 .

[13]  Charles E. Cook,et al.  Radar Signals: An Introduction to Theory and Application , 1967 .

[14]  M. O'Donnell,et al.  Coded excitation system for improving the penetration of real-time phased-array imaging systems , 1992, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[15]  Abraham Lempel,et al.  On Fast M-Sequence Transforms , 1998 .

[16]  A. Viterbi.  CDMA: Principles of Spread Spectrum Communication , 1995 .

[17]  Sergio Callegari,et al.  From chirps to random-FM excitations in pulse compression ultrasound systems , 2012, 2012 IEEE International Ultrasonics Symposium.