A swept frequency multiplication technique for air-coupled ultrasonic NDE

A new technique has been investigated for improving the signals that can be obtained in air-coupled nondestruction evaluation (NDE). This relies on the wide bandwidth available from polymer-filmed capacitive transducers. The technique relies on a swept-frequency "chirp" signal, which is transmitted from a transducer in air. The new technique differs from existing time-domain correlation techniques, such as pulse compression, in that a single multiplication process is performed in the time domain to give a difference frequency signal. This then can be isolated easily in the frequency domain. It will be demonstrated that this new swept frequency multiplication (SFM) approach gives the potential for rapid air-coupled imaging.

[1]  Charles E. Cook,et al.  Pulse Compression-Key to More Efficient Radar Transmission , 1960, Proceedings of the IRE.

[2]  C. Wykes,et al.  Diagnostic measurements in capacitive transducers , 1993 .

[3]  Anthony Gachagan,et al.  An evaluation of 1-3 connectivity composite transducers for air-coupled ultrasonic applications , 1996 .

[4]  De Yuhas,et al.  High resolution air-coupled ultrasonic imaging of thin materials , 2002 .

[5]  Evaluation of a pulse coding technique for spacial structure characterization , 1994, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[6]  S. Venkatraman,et al.  Combining pulse compression and adaptive drive signal design to inverse filter the transducer system response and improve resolution in medical ultrasound , 2006, Medical and Biological Engineering and Computing.

[7]  T. Folkestad,et al.  Chirp excitation of ultrasonic probes and algorithm for filtering transit times in high-rangeability gas flow metering , 1993, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  S. W. Smith,et al.  Multilayered PZT/polymer composites to increase signal to noise ratio and resolution for medical ultrasound transducers , 1998, 1998 IEEE Ultrasonics Symposium. Proceedings (Cat. No. 98CH36102).

[9]  David A. Hutchins,et al.  High resolution air-coupled ultrasonic imaging of thin materials , 2002, 2002 IEEE Ultrasonics Symposium, 2002. Proceedings..

[10]  D. Schindel,et al.  The design and characterization of micromachined air-coupled capacitance transducers , 1995, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[11]  E Blomme,et al.  Recent observations with air-coupled NDE in the frequency range of 650 kHz to 1.2 mHz. , 2002, Ultrasonics.

[12]  D. A. Hutchins,et al.  Preliminary studies of a novel air-coupled ultrasonic inspection system for food containers , 2002 .

[13]  D. Schindel,et al.  The use of broadband acoustic transducers and pulse-compression techniques for air-coupled ultrasonic imaging. , 2001, Ultrasonics.

[14]  G. Hayward,et al.  Characterization of air-coupled transducers , 1996, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[15]  P. Pedersen,et al.  Impedance‐matching properties of an inhomogeneous matching layer with continuously changing acoustic impedance , 1982 .

[16]  R I Macdonald,et al.  Frequency domain optical reflectometer. , 1981, Applied optics.

[17]  David A. Hutchins,et al.  Surface metrology using reflected ultrasonic signals in air , 2002 .

[18]  Mahesh C. Bhardwaj,et al.  Ultrasonic analysis of plastics, rubbers and composites by non‐contact analyzer ‐ the NCA 1000 , 1999 .

[19]  Helmut Ermert,et al.  The optimum bandwidth of chirp signals in ultrasonic applications , 1993 .