Journal ArticleDOI
Chirp signal matching and signal power optimization in pulse-echo mode ultrasonic nondestructive testing
M. Pollakowski,Helmut Ermert +1 more
TLDR
In this paper, the authors proposed two methods to improve the overall efficiency of an ultrasonic pulse-echo system using nonlinear frequency modulation and square wave chirps derived from sine type chirp signals.Abstract:
Chirp pulse compression is a signal correlation technique that uses frequency modulated pulses as transmitted signals. Usually, signals with linear frequency modulation are applied. They can be generated rather easily, but their spectra are not totally matched to the transfer function of ultrasonic systems. In pulse-echo mode operation, with signal duration and consequently the time-bandwidth product being critical parameters, waveforms should be applied which make full use of the available power and bandwidth resources. We report here two methods to improve the overall efficiency of an ultrasonic pulse-echo system. Transmitter signals with constant amplitude level and nonlinear frequency modulation can be generated in such a way that they are spectrally matched to the system. A formula for the calculation of such a matched nonlinear chirp signal is presented. This modulation scheme also leads to a side-lobe level reduction of the compressed pulses. The application of square wave chirps derived from sine type chirps yields an additional gain of echo signal amplitude. Moreover, the complexity of the signal generation hardware is reduced. The methods are illustrated by an example. >read more
Citations
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Journal ArticleDOI
Use of modulated excitation signals in medical ultrasound. Part I: basic concepts and expected benefits
TL;DR: This paper, the first from a series of three papers on the application of coded excitation signals in medical ultrasound, discusses the basic principles and ultrasound-related problems of pulse compression and the selection of coded waveforms suitable for ultrasound imaging.
Journal ArticleDOI
SARUS: A synthetic aperture real-time ultrasound system
Jørgen Arendt Jensen,Hans Holten-Lund,R. T. Nilsson,M. Hansen,U. D. Larsen,R. P. Domsten,B.G. Tomov,Matthias Bo Stuart,Svetoslav Ivanov Nikolov,Michael Johannes Pihl,Yigang Du,Joachim Hee Rasmussen,Morten Fischer Rasmussen +12 more
TL;DR: The Synthetic Aperture Real-time Ultrasound System (SARUS) for acquiring and processing synthetic aperture data for research purposes is described, along with its performance for SA, nonlinear, and 3-D flow estimation imaging.
Journal ArticleDOI
The use of broadband acoustic transducers and pulse-compression techniques for air-coupled ultrasonic imaging.
TL;DR: Capacitance transducers were used to generate wide bandwidth swept-frequency signals in air, which were then used to measure and image solid samples in through transmission, demonstrating that such signal processing techniques lead to an improvement in the signal to noise ratio and timing accuracy for air-coupled testing.
Journal ArticleDOI
Chirp excitation of ultrasonic guided waves
TL;DR: Broadband and narrowband chirp excitations are utilized to address the need to both test at multiple frequencies and achieve a high signal-to-noise ratio to minimize acquisition time.
Synthetic aperture imaging algorithms : with application to wide bandwidth sonar
TL;DR: The algorithms used in the generation of synthetic aperture radar (SAR) images are derived in their wide bandwidth forms and it is shown that these more efficient algorithms can be used to form diffraction limited SAS images.
References
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Journal ArticleDOI
Coded excitation system for improving the penetration of real-time phased-array imaging systems
TL;DR: A very simple coded excitation for phased arrays based on the principles of 'pseudochirp' excitation and equalization filtering is described, capable of SNR improvements of about 15 dB with range sidelobe levels acceptable for many medical imaging applications.
Journal ArticleDOI
Acoustic imaging for nondestructive evaluation
TL;DR: In this article, the application of acoustic imaging techniques to non-destructive testing (NDT) of materials is discussed and it is shown that the use of imaging techniques makes it possible to locate the position of flaws quickly and accurately.
Journal ArticleDOI
A new filter design technique for coded excitation systems
TL;DR: To increase range resolution and produce acceptable range sidelobe levels, filtering techniques rather than direct complex correlation are applied in coded excitation systems.
Journal ArticleDOI
Digital generation of high time-bandwidth product linear FM waveforms for radar altimeters
H.D. Griffiths,W.J. Bradford +1 more
TL;DR: An analysis is developed to relate the level of phase and amplitude errors to the permissible range sidelobe level, showing that considerably greater phase errors can be tolerated than for conventional pulse compression radars.
Journal ArticleDOI
A Matched-Filter Pulse-Compression System Using a Nonlinear FM Waveform
TL;DR: In this paper, the design and performance of a matched-filter pulse-compression system having essentially zero mismatch loss are presented, and the difficulty of achieving the required nonlinear time delay dispersion is overcome by synthesizing the dispersive network as a cascade of all-pass networks.