Grating-lobes reduction by application of Phase Coherence Factors

Camacho, J.; Parrilla, M.; Fritsch, C.

doi:10.1109/ultsym.2009.5441770

Cited by 29 publications

(9 citation statements)

References 6 publications

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“…Although complying with this requirement, the monostatic SAFT process results in the formation of artefacts in the image, which reduce the contrast [29]. For this reason, the use of SCF is essential for suppressing spurious indications in the output image, as well as improving the resolution and contrast [30,31]. These features, even allow working with larger separations of dy, reducing the required bandwidth and processing power while maintaining a good contrast.…”

Section: A Phase Coherence Imaging (Pci)mentioning

confidence: 99%

“…In both cases, the quality of the obtained C-Scan images is further improved using the PCI technique ( Figure 17B and 18B), particularly the detection of hole #2, which is near to the surface, and hole #1, which is masked by the background artefact that surrounds it. Finally, the Mayavi [31] application was used for 3D representation (Figure 19). The processed data cube is positioned in a 3D space, in which each pixel constitutes a voxel.…”

Section: Inspection Of a Nuclear Couponmentioning

confidence: 99%

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Improving elevation resolution in phased-array inspections for NDT

Brizuela

Camacho

Cosarinsky

et al. 2019

NDT & E International

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The Phased Array Ultrasonic Technique (PAUT) offers great advantages over the conventional ultrasound technique (UT), particularly because of beam focusing, beam steering and electronic scanning capabilities. However, the 2D images obtained have usually low resolution in the direction perpendicular to the array elements, which limits the inspection quality of large components by mechanical scanning. This paper describes a novel approach to improve image quality in these situations, by combining three ultrasonic techniques: Phased Array with dynamic depth focusing in reception, Synthetic Aperture Focusing Technique (SAFT) and Phase Coherence Imaging (PCI). To be applied with conventional NDT arrays (1D and non-focused in elevation) a special mask to produce a wide beam in the movement direction was designed and analyzed by simulation and experimentally. Then, the imaging algorithm is presented and validated by the inspection of test samples. The obtained images quality is comparable to that obtained with an equivalent matrix array, but using conventional NDT arrays and equipments, and implemented in real time.

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Section: A Phase Coherence Imaging (Pci)mentioning

confidence: 99%

Section: Inspection Of a Nuclear Couponmentioning

confidence: 99%

Improving elevation resolution in phased-array inspections for NDT

Brizuela

Camacho

Cosarinsky

et al. 2019

NDT & E International

Self Cite

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“…Another approach for suppressing grating lobes uses nonsinusoidal transmit signals that also remove the periodic pattern in the beamformer output [43]. Grating lobe suppression can also be accomplished via adaptive beamforming that applies a weighting factor either to the echoes received on each sensor element [44,45] or to the transmit aperture [46,47]. Previous work in optimizing array design or performance in ocean acoustic remote sensing applications are based on numerical simulation for a given signal with deterministic frequency or bandwidth [36][37][38][39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

Angular Resolution Enhancement Provided by Nonuniformly-Spaced Linear Hydrophone Arrays in Ocean Acoustic Waveguide Remote Sensing

Wang

Ratilal

2017

Remote Sensing

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Uniformly-spaced apertures or subapertures of large, densely-sampled, discrete linear receiver arrays are often used in remote sensing to increase the signal-to-noise ratio (SNR) by coherent beamforming that reduces noise coming from directions outside the signal beam. To avoid spatial aliasing or the presence of grating lobes in real spatial directions, the uniformly-spaced array inter-element spacing d sets a limit on the maximum frequency f max < c/2d of signals suitable for beamforming with the array, where c is the medium's wave propagation speed. Here, we show that a nonuniformly-spaced array, for instance, formed by combining multiple uniformly-spaced subapertures of a nested linear array, can significantly enhance the array angular resolution while simultaneously avoiding dominant grating lobes in real angular space, even for signals with frequencies beyond the maximum that the array is designed for. The array gain, beam width, and maximum grating lobe height are quantified for the Office of Naval Research Five Octave Research Array (ONR-FORA) for various combinations of its uniformly-spaced subapertures, leading to nonuniformly-spaced subarrays. Illustrative examples show angular resolution enhancement provided by the nonuniformly-spaced ONR-FORA subarrays over that of its uniformly-spaced individual subaperture counterparts in both active and passive ocean acoustic waveguide remote sensing, drawn from measurements in the Gulf of Maine 2006 Experiment.

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“…Extremely high sparsity can be achieved by irregularly distributed MIMO arrays, since the randomness of element layouts tends to share the energy of sidelobes amongst the elements, and the sidelobes and grating lobes will be suppressed according to the projection slice method [ 12 ]. Finding approaches to improve the precision of 3D images has been an area of active research focus for irregularly distributed arrays, resulting in a number of methods such as the modified Kirchhoff Migration Algorithm [ 13 ], and the grating lobes migration technology [ 14 , 15 , 16 ]. In terms of efficiency, fast back projection algorithms seem to be attractive [ 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

Dimension-Factorized Range Migration Algorithm for Regularly Distributed Array Imaging

Guo

Wang

Chang

et al. 2017

Sensors

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The two-dimensional planar MIMO array is a popular approach for millimeter wave imaging applications. As a promising practical alternative, sparse MIMO arrays have been devised to reduce the number of antenna elements and transmitting/receiving channels with predictable and acceptable loss in image quality. In this paper, a high precision three-dimensional imaging algorithm is proposed for MIMO arrays of the regularly distributed type, especially the sparse varieties. Termed the Dimension-Factorized Range Migration Algorithm, the new imaging approach factorizes the conventional MIMO Range Migration Algorithm into multiple operations across the sparse dimensions. The thinner the sparse dimensions of the array, the more efficient the new algorithm will be. Advantages of the proposed approach are demonstrated by comparison with the conventional MIMO Range Migration Algorithm and its non-uniform fast Fourier transform based variant in terms of all the important characteristics of the approaches, especially the anti-noise capability. The computation cost is analyzed as well to evaluate the efficiency quantitatively.

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Grating-lobes reduction by application of Phase Coherence Factors

Cited by 29 publications

References 6 publications

Improving elevation resolution in phased-array inspections for NDT

Improving elevation resolution in phased-array inspections for NDT

Angular Resolution Enhancement Provided by Nonuniformly-Spaced Linear Hydrophone Arrays in Ocean Acoustic Waveguide Remote Sensing

Dimension-Factorized Range Migration Algorithm for Regularly Distributed Array Imaging

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