The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Andrea Trucco - One of the best experts on this subject based on the ideXlab platform.
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Global synthesis of superdirective frequency-invariant Beam Patterns
The Journal of the Acoustical Society of America, 2008Co-Authors: Marco Crocco, S. Repetto, Andrea TruccoAbstract:Frequency-invariant Beam Patterns are often required by systems using an array of sensors to process broadband signals. If the spatial aperture is shorter than the involved wavelengths, the use of a superdirective Beam Pattern is essential to attain an efficient system. In this context, robustness to array imperfections is a crucial feature. In the literature, only a few approaches have been proposed to design a robust, superdirective, frequency-invariant Beamformer, based on a filter and sum architecture: in all of them, the frequency invariance is achieved imposing an a priori desired Beam Pattern. However the choice of a suitable desired Beam Pattern is not trivial and depends on the specific design case: an improper selection of the desired Beam Pattern can produce unsatisfactory performances. We propose a new method of global synthesis, computationally inexpensive, allowing to design a robust broadband Beam Pattern with an optimal trade-off between the frequency invariance and the directivity, without the need of imposing a priori a desired Beam Pattern. The results show that the synthesized Beam Patterns have a directivity, a frequency-invariance, and a robustness that are very similar to or better than those of the Beam Patterns obtained by the literature methods.
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Designing superdirective microphone arrays with a frequency-invariant Beam Pattern
IEEE Sensors Journal, 2006Co-Authors: S. Repetto, Andrea TruccoAbstract:Frequency-invariant Beam Patterns are often required in systems using an array of sensors to process broadband signals. Although several methods have been proposed to design a broadband Beamformer [typically realized with a finite-impulse-response (FIR) filter for each sensor] with a frequency-invariant Beam Pattern (FIBP), until now the case in which the spatial aperture is shorter than the involved wavelengths has very rarely been addressed. In such a case, the use of a superdirective Beam Pattern is essential for attaining an efficient system. In this paper, a novel method to design a broadband Beamformer that produces an FIBP for a data-independent superdirective array is proposed and compared with other potential approaches. The method generates a far-field Beam Pattern that reproduces the desired profile over a very wide frequency band, also if the array is shorter than the wavelength. Two steps are necessary: 1) the generation of many apodizing windows at different frequency values by a stochastic method and 2) the synthesis of the FIR filters with the Parks-McClellan technique. At the end of the design chain, the very simple implementation and the robustness of the attained broadband Beamformer to array imperfections increases the applicability of the system, for instance, in audio signal processing using microphone arrays
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Computation and Properties of the Wide-Band Beam Pattern
Acoustical Imaging, 2004Co-Authors: Gabriella Cincotti, Andrea TruccoAbstract:The definition, computation and properties of the Beam Pattern of an ultrasonic imaging system working under wide-band conditions are addressed. After defining the Beam Pattern as the total energy of the Beam signals, a fast and flexible method to compute such a Beam Pattern is proposed that works correctly for whatever weighting window, pulse shape, and inter-element spacing. Moreover, the proposed method is extended to the computation of the Beam Pattern area, allowing to asses the effects of different weighting windows and pulse waveforms. In particular, if a rectangular pulse envelope is adopted, this paper demonstrates that, like under narrow-band conditions, the Beam Pattern area is minimum when a uniform weighting window is applied.
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Aperture and element minimization in linear sparse arrays with desired Beam Patterns
Ultrasonics, 2000Co-Authors: Andrea TruccoAbstract:In this paper, an optimization method aimed at designing aperiodic linear sparse arrays is proposed that is based on the stochastic optimization methodology called simulated annealing. Such a method optimizes the positions and the weight coefficients of each element of a linear array in order to obtain a Beam Pattern that meets given requirements. Moreover, while positions and weights are optimized, minimization of both the number of elements and the spatial aperture is carried out. In this way, a Beam Pattern without grating lobes and close to the desired one is produced using a small number of elements and a short aperture. The results obtained are impressive in terms of improvement of array characteristics and performance over those reported in the literature, while a great flexibility in defining the desired Beam Pattern is allowed. Finally, it is proved that the array configurations need a number of elements very close to the absolute minimum to achieve the desired Beam Pattern.
Robert C Gisner - One of the best experts on this subject based on the ideXlab platform.
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echolocation signals and transmission Beam Pattern of a false killer whale pseudorca crassidens
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Michele Blonz, Jeffery L Pawloski, Paul E Nachtigall, Robert C GisnerAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured. Type‐1 signals had a single low‐frequency peak at 40±9 kHz and a low‐amplitude shoulder at high frequencies. Type‐2 signals had a bimodal frequency characteristic with a primary peak at 46±7 kHz and a secondary peak at 88±13 kHz. Type‐3 signals were also bimodal but with a primary peak at 100±7 kHz and a secondary peak at 49±9 kHz. Type‐4 signals had a single high‐frequency peak at 104±7 kHz. The center frequency of the signals were found to be linearly corre...
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echolocation signals and transmission Beam Pattern of a false killer whale pseudorca crassidens
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Michele Blonz, Jeffery L Pawloski, Paul E Nachtigall, Robert C GisnerAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured. Type‐1 signals had a single low‐frequency peak at 40±9 kHz and a low‐amplitude shoulder at high frequencies. Type‐2 signals had a bimodal frequency characteristic with a primary peak at 46±7 kHz and a secondary peak at 88±13 kHz. Type‐3 signals were also bimodal but with a primary peak at 100±7 kHz and a secondary peak at 49±9 kHz. Type‐4 signals had a single high‐frequency peak at 104±7 kHz. The center frequency of the signals were found to be linearly correlated to the peak‐to‐peak source level, increasing with increasing source level. The major axis of the vertical Beam was directed slightly downward between 0 and −5°, in contrast to the +5 to 10° for Tursiops and Delphinapterus. The Beam in the horizontal plane was directed forward between 0° and −5°. In both planes, the type‐1 signals had the broadest Beam Pattern, followed by the type‐2 and type‐3 signals, with the narrowest Beam Pattern being exhibited by the type‐4 signals. The Beam Pattern in the horizontal plane was much narrower than the Beam Pattern in the vertical plane.
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Transmission Beam Pattern of a false killer whale
Journal of the Acoustical Society of America, 1993Co-Authors: Whitlow W. L. Au, Robert C Gisner, Ted W Cranford, Jeffery L Pawloski, Paul E NachtigallAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, with the whale performing a discrimination task. The width of the Beams in both planes were similar to those of the Atlantic bottlenose dolphin (Tursiops truncatus), and broader than those of the beluga whale (Delphinapterus leucas). The major axis of the vertical Beam was directed slightly downwards between 0° and −5°, in contrast to the +5 to 10° for Tursiops and Delphinapterus. The Beam in the horizontal plane was directed forward. Differences in the fatty structure of the melon of Pseudorca, Tursiops, and Delphinapterus could explain differences in the elevation angle of the vertical Beam...
Qing Huo Liu - One of the best experts on this subject based on the ideXlab platform.
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fast pencil Beam Pattern synthesis of large unequally spaced antenna arrays
IEEE Transactions on Antennas and Propagation, 2013Co-Authors: Kai Yang, Zhiqin Zhao, Qing Huo LiuAbstract:Reducing the computational cost of large array Pattern synthesis is attractive in many applications. In this paper, a fast pencil Beam Pattern synthesis method for large nonuniform antenna arrays is proposed. This method is based on an interpolation in a least square sense and iterative fast Fourier transform (FFT), i.e., interpolate the nonuniform distributed elements into uniform virtual elements, and then apply FFT to synthesis the uniform array. Thanks to the efficiency of FFT, the proposed method is much faster and can handle much larger arrays than the existing methods. To guarantee the interpolation accuracy, the choice of the interpolation parameters is discussed. Both linear and planar nonuniform array examples are shown to validate the advantages of the proposed method.
Whitlow W. L. Au - One of the best experts on this subject based on the ideXlab platform.
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echolocation signals and transmission Beam Pattern of a false killer whale pseudorca crassidens
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Michele Blonz, Jeffery L Pawloski, Paul E Nachtigall, Robert C GisnerAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured. Type‐1 signals had a single low‐frequency peak at 40±9 kHz and a low‐amplitude shoulder at high frequencies. Type‐2 signals had a bimodal frequency characteristic with a primary peak at 46±7 kHz and a secondary peak at 88±13 kHz. Type‐3 signals were also bimodal but with a primary peak at 100±7 kHz and a secondary peak at 49±9 kHz. Type‐4 signals had a single high‐frequency peak at 104±7 kHz. The center frequency of the signals were found to be linearly corre...
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echolocation signals and transmission Beam Pattern of a false killer whale pseudorca crassidens
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Michele Blonz, Jeffery L Pawloski, Paul E Nachtigall, Robert C GisnerAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured. Type‐1 signals had a single low‐frequency peak at 40±9 kHz and a low‐amplitude shoulder at high frequencies. Type‐2 signals had a bimodal frequency characteristic with a primary peak at 46±7 kHz and a secondary peak at 88±13 kHz. Type‐3 signals were also bimodal but with a primary peak at 100±7 kHz and a secondary peak at 49±9 kHz. Type‐4 signals had a single high‐frequency peak at 104±7 kHz. The center frequency of the signals were found to be linearly correlated to the peak‐to‐peak source level, increasing with increasing source level. The major axis of the vertical Beam was directed slightly downward between 0 and −5°, in contrast to the +5 to 10° for Tursiops and Delphinapterus. The Beam in the horizontal plane was directed forward between 0° and −5°. In both planes, the type‐1 signals had the broadest Beam Pattern, followed by the type‐2 and type‐3 signals, with the narrowest Beam Pattern being exhibited by the type‐4 signals. The Beam Pattern in the horizontal plane was much narrower than the Beam Pattern in the vertical plane.
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Transmission Beam Pattern of a false killer whale
Journal of the Acoustical Society of America, 1993Co-Authors: Whitlow W. L. Au, Robert C Gisner, Ted W Cranford, Jeffery L Pawloski, Paul E NachtigallAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, with the whale performing a discrimination task. The width of the Beams in both planes were similar to those of the Atlantic bottlenose dolphin (Tursiops truncatus), and broader than those of the beluga whale (Delphinapterus leucas). The major axis of the vertical Beam was directed slightly downwards between 0° and −5°, in contrast to the +5 to 10° for Tursiops and Delphinapterus. The Beam in the horizontal plane was directed forward. Differences in the fatty structure of the melon of Pseudorca, Tursiops, and Delphinapterus could explain differences in the elevation angle of the vertical Beam...
Paul E Nachtigall - One of the best experts on this subject based on the ideXlab platform.
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echolocation signals and transmission Beam Pattern of a false killer whale pseudorca crassidens
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Michele Blonz, Jeffery L Pawloski, Paul E Nachtigall, Robert C GisnerAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured. Type‐1 signals had a single low‐frequency peak at 40±9 kHz and a low‐amplitude shoulder at high frequencies. Type‐2 signals had a bimodal frequency characteristic with a primary peak at 46±7 kHz and a secondary peak at 88±13 kHz. Type‐3 signals were also bimodal but with a primary peak at 100±7 kHz and a secondary peak at 49±9 kHz. Type‐4 signals had a single high‐frequency peak at 104±7 kHz. The center frequency of the signals were found to be linearly corre...
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echolocation signals and transmission Beam Pattern of a false killer whale pseudorca crassidens
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Michele Blonz, Jeffery L Pawloski, Paul E Nachtigall, Robert C GisnerAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured. Type‐1 signals had a single low‐frequency peak at 40±9 kHz and a low‐amplitude shoulder at high frequencies. Type‐2 signals had a bimodal frequency characteristic with a primary peak at 46±7 kHz and a secondary peak at 88±13 kHz. Type‐3 signals were also bimodal but with a primary peak at 100±7 kHz and a secondary peak at 49±9 kHz. Type‐4 signals had a single high‐frequency peak at 104±7 kHz. The center frequency of the signals were found to be linearly correlated to the peak‐to‐peak source level, increasing with increasing source level. The major axis of the vertical Beam was directed slightly downward between 0 and −5°, in contrast to the +5 to 10° for Tursiops and Delphinapterus. The Beam in the horizontal plane was directed forward between 0° and −5°. In both planes, the type‐1 signals had the broadest Beam Pattern, followed by the type‐2 and type‐3 signals, with the narrowest Beam Pattern being exhibited by the type‐4 signals. The Beam Pattern in the horizontal plane was much narrower than the Beam Pattern in the vertical plane.
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Transmission Beam Pattern of a false killer whale
Journal of the Acoustical Society of America, 1993Co-Authors: Whitlow W. L. Au, Robert C Gisner, Ted W Cranford, Jeffery L Pawloski, Paul E NachtigallAbstract:The echolocation transmission Beam Pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the Beam Pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, with the whale performing a discrimination task. The width of the Beams in both planes were similar to those of the Atlantic bottlenose dolphin (Tursiops truncatus), and broader than those of the beluga whale (Delphinapterus leucas). The major axis of the vertical Beam was directed slightly downwards between 0° and −5°, in contrast to the +5 to 10° for Tursiops and Delphinapterus. The Beam in the horizontal plane was directed forward. Differences in the fatty structure of the melon of Pseudorca, Tursiops, and Delphinapterus could explain differences in the elevation angle of the vertical Beam...