Title :
Real-time analysis signal processor for ultrasonic nondestructive testing
Author :
Duncan, Michael G.
Author_Institution :
Martin Marietta Energy Syst. Inc., Oak Ridge, TN, USA
fDate :
12/1/1990 12:00:00 AM
Abstract :
Hilbert transform processors were developed to improve flaw detection in parts by sensing the rate of total energy arrival. Analytic signal processing is used to improve pulse resolution. A real-time analytic processor was built using single-sideband (SBB) AM techniques. An upper sideband processor using the filter method to maximize signal bandwidth and in which the lower sideband aliases was built. This processor has a transducer bandwidth of 0.5 to 20 MHz and can resolve echoes 90-ns apart. The spurious products of practical mixers and amplifiers make the aliased approach impractical due to high noise and distortion. By using a bandpass filter after the mixer, distortion is reduced. A processor built with a lower sideband filter method yielded the lowest distortion and noise. The lower sideband processor has a bandwidth of 2 to 42 MHz and can resolve echoes 60-ns apart. With a single-cycle tone-burst processor input, ringing in the IF filter causes temporal asymmetry of the output pulse, while ringing in the detector filter causes ringing in the output pulse. Performance is expected to improve through the design of optimized filters. The ringing is less with ultrasonic echoes, because they do not start and stop as abruptly as a tone burst
Keywords :
automatic test equipment; band-pass filters; computerised signal processing; echo; flaw detection; real-time systems; signal processing equipment; transforms; ultrasonic materials testing; 0.5 to 42 MHz; Hilbert transform processors; IF filter; SBB; analysis signal processor; bandpass filter; flaw detection; manufacturing parts testing; optimized filters; real-time; ringing; single sideband AM; single-cycle tone-burst processor input; temporal asymmetry; ultrasonic echoes; ultrasonic nondestructive testing; upper sideband processor; Acoustic reflection; Acoustic transducers; Bandwidth; Energy resolution; Nondestructive testing; Pulse measurements; Signal analysis; Signal processing; Surface waves; Ultrasonic transducers;
Journal_Title :
Instrumentation and Measurement, IEEE Transactions on