The Experts below are selected from a list of 1572 Experts worldwide ranked by ideXlab platform
Jingdong Chen - One of the best experts on this subject based on the ideXlab platform.
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Window-Based Constant Beamwidth Beamformer
'MDPI AG', 2019Co-Authors: Tao Long, Israel Cohen, Baruch Berdugo, Yan Yang, Jingdong ChenAbstract:Beamformers have been widely used to enhance signals from a desired direction and suppress noise and interfering signals from other directions. Constant beamwidth beamformers enable a fixed beamwidth over a wide range of frequencies. Most of the existing approaches to design constant beamwidth beamformers are based on optimization algorithms with high computational complexity and are often sensitive to microphone mismatches. Other existing methods are based on adjusting the number of sensors according to the frequency, which simplify the design, but cannot control the sidelobe level. Here, we propose a window-based technique to attain the beamwidth constancy, in which different shapes of standard window functions are applied for different frequency bins as the real weighting coefficients of microphones. Thereby, not only do we keep the beamwidth constant, but we also control the sidelobe level. Simulation results show the advantages of our method compared with existing methods, including lower sidelobe level, higher Directivity Factor, and higher white noise gain
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on the design of robust steerable frequency invariant beampatterns with concentric circular microphone arrays
International Conference on Acoustics Speech and Signal Processing, 2018Co-Authors: Gongping Huang, Jingdong Chen, Jacob BenestyAbstract:This paper studies the problem of frequency-invariant beamforming with concentric circular microphone arrays (CCMAs). We develop a beamforming algorithm based on an optimal approximation of the beamformer's beampattern with the Jacobi-Anger expansion. In comparison with the existing frequency-invariant beamformers with either circular microphone arrays (CMAs) or CCMAs, the developed algorithm offers the following advantages: 1) it can mitigate the deep-null problem encountered in CMAs and therefore has a consistent Directivity Factor over the frequency range of speech signals; 2) it is more flexible in terms of steering flexibility and the resulting beampattern can be steered to any direction; and 3) it does not require the microphones in different rings of the CCMA to be aligned, which is very useful in practice, particularly when microphone arrays with small and compact apertures have to be used.
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on the design of frequency invariant beampatterns with uniform circular microphone arrays
IEEE Transactions on Audio Speech and Language Processing, 2017Co-Authors: Gongping Huang, Jacob Benesty, Jingdong ChenAbstract:This paper deals with two critical issues about uniform circular arrays (UCAs): frequency-invariant response and steering flexibility. It focuses on some optimal design of frequency-invariant beampatterns in any desired direction along the sensor plane. The major contributions are as follows. 1) We explain how to include the steering information in the desired Directivity pattern. 2) We show that the optimal approximation of the beamformer's beampattern with a UCA from a least-squares error perspective is the Jacobi–Anger expansion. 3) We develop an approach to the design of any desired symmetric Directivity pattern, where the deduced beampattern is almost frequency invariant and its main beam can be pointed to any wanted direction in the sensor plane. 4) With the proposed approach, we derive an explicit form of the white noise gain (WNG) and the Directivity Factor (DF), and explain clearly the white noise amplification problem at low frequencies and the DF degradation at high frequencies. The analysis also indicates that increasing the number of microphones can always improve the WNG. We show that the proposed method is a generalization of circular differential microphone arrays. The relationship between the proposed method and the so-called circular harmonics beamformers is also discussed.
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Subspace superdirective beamformers based on joint diagonalization
2016 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2016Co-Authors: Changlei Li, Gongping Huang, Jacob Benesty, Jingdong ChenAbstract:Although they have been intensively studied and used in many applications due to their high Directivity Factor (DF), superdirective beamformers are sensitive to sensor noise and mismatch between sensors. This paper studies the problem of superdirective beamforming combined with the joint diagonalization method. We develop a subspace superdirective beamforming approach, which can achieve a good compromise between a high DF and white noise amplification. Simulations are performed to justify our theoretical analysis and demonstrate the good properties of this subspace superdirective beamforming approach.
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Design of Robust Differential Microphone Arrays
2016Co-Authors: Liheng Zhao, Jacob Benesty, Jingdong Chen, Senior MemberAbstract:Abstract—Differential microphone arrays (DMAs), due to their small size and enhanced Directivity, are quite promising in speech enhancement applications. However, it is well known that differ-ential beamformers have the drawback of white noise amplifica-tion, which is a major issue in the processing of wideband signals such as speech. In this paper, we focus on the design of robust DMAs. Based on the Maclaurin’s series approximation and fre-quency-independent beampatterns, the robust first-, second-, and third-order DMAs are proposed by using more microphones than the order plus one, and the corresponding minimum-norm filters are derived. Compared to the traditional DMAs, the proposed de-signs are more robust with respect to white noise amplification while they are capable of achieving similar directional gains. Index Terms—Beamforming, beampattern, differential micro-phone arrays (DMAs), Directivity Factor, first-order DMA, robust DMAs, second-order DMA, third-order DMA, white noise gain. I
Jacob Benesty - One of the best experts on this subject based on the ideXlab platform.
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on the design of robust steerable frequency invariant beampatterns with concentric circular microphone arrays
International Conference on Acoustics Speech and Signal Processing, 2018Co-Authors: Gongping Huang, Jingdong Chen, Jacob BenestyAbstract:This paper studies the problem of frequency-invariant beamforming with concentric circular microphone arrays (CCMAs). We develop a beamforming algorithm based on an optimal approximation of the beamformer's beampattern with the Jacobi-Anger expansion. In comparison with the existing frequency-invariant beamformers with either circular microphone arrays (CMAs) or CCMAs, the developed algorithm offers the following advantages: 1) it can mitigate the deep-null problem encountered in CMAs and therefore has a consistent Directivity Factor over the frequency range of speech signals; 2) it is more flexible in terms of steering flexibility and the resulting beampattern can be steered to any direction; and 3) it does not require the microphones in different rings of the CCMA to be aligned, which is very useful in practice, particularly when microphone arrays with small and compact apertures have to be used.
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on the design of frequency invariant beampatterns with uniform circular microphone arrays
IEEE Transactions on Audio Speech and Language Processing, 2017Co-Authors: Gongping Huang, Jacob Benesty, Jingdong ChenAbstract:This paper deals with two critical issues about uniform circular arrays (UCAs): frequency-invariant response and steering flexibility. It focuses on some optimal design of frequency-invariant beampatterns in any desired direction along the sensor plane. The major contributions are as follows. 1) We explain how to include the steering information in the desired Directivity pattern. 2) We show that the optimal approximation of the beamformer's beampattern with a UCA from a least-squares error perspective is the Jacobi–Anger expansion. 3) We develop an approach to the design of any desired symmetric Directivity pattern, where the deduced beampattern is almost frequency invariant and its main beam can be pointed to any wanted direction in the sensor plane. 4) With the proposed approach, we derive an explicit form of the white noise gain (WNG) and the Directivity Factor (DF), and explain clearly the white noise amplification problem at low frequencies and the DF degradation at high frequencies. The analysis also indicates that increasing the number of microphones can always improve the WNG. We show that the proposed method is a generalization of circular differential microphone arrays. The relationship between the proposed method and the so-called circular harmonics beamformers is also discussed.
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Subspace superdirective beamformers based on joint diagonalization
2016 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2016Co-Authors: Changlei Li, Gongping Huang, Jacob Benesty, Jingdong ChenAbstract:Although they have been intensively studied and used in many applications due to their high Directivity Factor (DF), superdirective beamformers are sensitive to sensor noise and mismatch between sensors. This paper studies the problem of superdirective beamforming combined with the joint diagonalization method. We develop a subspace superdirective beamforming approach, which can achieve a good compromise between a high DF and white noise amplification. Simulations are performed to justify our theoretical analysis and demonstrate the good properties of this subspace superdirective beamforming approach.
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Design of Robust Differential Microphone Arrays
2016Co-Authors: Liheng Zhao, Jacob Benesty, Jingdong Chen, Senior MemberAbstract:Abstract—Differential microphone arrays (DMAs), due to their small size and enhanced Directivity, are quite promising in speech enhancement applications. However, it is well known that differ-ential beamformers have the drawback of white noise amplifica-tion, which is a major issue in the processing of wideband signals such as speech. In this paper, we focus on the design of robust DMAs. Based on the Maclaurin’s series approximation and fre-quency-independent beampatterns, the robust first-, second-, and third-order DMAs are proposed by using more microphones than the order plus one, and the corresponding minimum-norm filters are derived. Compared to the traditional DMAs, the proposed de-signs are more robust with respect to white noise amplification while they are capable of achieving similar directional gains. Index Terms—Beamforming, beampattern, differential micro-phone arrays (DMAs), Directivity Factor, first-order DMA, robust DMAs, second-order DMA, third-order DMA, white noise gain. I
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Combined Beamformers for Robust Broadband
2016Co-Authors: Regularized Superdirective Beamforming, Reuven Berkun, Israel Cohen, Jacob BenestyAbstract:Abstract—Superdirective fixed beamformers are known to attain high Directivity Factors, but are extremely sensitive to uncorrelated noise and slight errors in the array elements, which are modeled by the beamformer white noise gain measure. The delay-and-sum beamformer, on the other hand, manages to maxi-mize the white noise gain, but suffers from a very low Directivity Factor. In this paper, we discuss the design of a broadband beam-former which controls both the Directivity Factor and the white noise gain. We combine a regularized version of the superdirec-tive beamformer together with the delay-and-sum beamformer to create a robust regularized superdirective beamformer. We derive analytic closed-form expressions of the beamformer gain responses, and extend them to derive a beamformer with full control of the desired white noise gain or the Directivity Factor. The proposed approach offers a simple and robust broadband beamformer with controllable characteristics, shown here through persuasive simulation results. Index Terms—Beamforming, delay-and-sum beamformer, Directivity Factor, microphone arrays, robust superdirective beam-former, superdirective beamformer, supergain, white noise gain. I
V I Altunin - One of the best experts on this subject based on the ideXlab platform.
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giant pulses from psr b1937 21 with widths 15 nanoseconds and tb 5 1039 k the highest brightness temperature observed in the universe
The Astrophysical Journal, 2004Co-Authors: V A Soglasnov, M V Popov, N Bartel, W H Cannon, Yu A Novikov, V I Kondratiev, V I AltuninAbstract:Giant radio pulses of the millisecond pulsar B1937+21 were recorded with the S2 VLBI system at 1.65 GHz with NASA/JPL's 70 m radio telescope at Tidbinbilla, Australia. These pulses have been observed as strong as 65,000 Jy with widths ≤15 ns, corresponding to a brightness temperature of Tb ≥ 5 × 1039 K, the highest observed in the universe. The vast majority of these pulses occur in 5.8 and 8.2 μs windows at the very trailing edges of the regular main pulse and interpulse profiles, respectively. Giant pulses occur, in general, with a single spike. Only in one case of 309 was the structure clearly more complex. The cumulative distribution is fitted by a power law with index -1.40 ± 0.01 with a low-energy but no high-energy cutoff. We estimate that giant pulses occur frequently but are only rarely detected. When corrected for the Directivity Factor, 25 giant pulses are estimated to be generated in one neutron star revolution alone. The intensities of the giant pulses of the main pulses and interpulses are not correlated with each other nor with the intensities or energies of the main pulses and interpulses themselves. Their radiation energy density can exceed 300 times the plasma energy density at the surface of the neutron star and can even exceed the magnetic field energy density at that surface. We therefore do not think that the generation of giant pulses is linked to the plasma mechanisms in the magnetosphere. Instead we suggest that it is directly related to discharges in the polar cap region of the pulsar.
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giant pulses from psr b1937 21 with widths 5 x 10 39 k the highest brightness temperature observed in the universe
arXiv: Astrophysics, 2004Co-Authors: V A Soglasnov, M V Popov, N Bartel, W H Cannon, Yu A Novikov, V I Kondratiev, V I AltuninAbstract:Giant radio pulses of the millisecond pulsar B1937+21 were recorded with the S2 VLBI system at 1.65 GHz with NASA/JPL's 70-m radio telescope at Tidbinbilla, Australia. These pulses have been observed as strong as 65000 Jy with widths = 5 x 10^39 K, the highest observed in the universe. The vast majority of these pulses occur in a 5.8 mcs and 8.2 mcs window at the very trailing edges of the regular main pulse and interpulse profiles, respectively. Giant pulses occur in general with a single spike. Only in one case out of 309 was the structure clearly more complex. The cumulative distribution is fit by a power law with index -1.40 +/- 0.01 with a low-energy but no high-energy cutoff. We estimate that giant pulses occur frequently but are only rarely detected. When corrected for the Directivity Factor, 25 giant pulses are estimated to be generated in one neutron star revolution alone. The intensities of the giant pulses of the main pulses and interpulses are not correlated with each other nor with the intensities or energies of the main pulses and interpulses themselves. Their radiation energy density can exceed 300 times the plasma energy density at the surface of the neutron star and can even exceed the magnetic field energy density at that surface. We therefore do not think that the generation of giant pulses is linked to the plasma mechanisms in the magnetosphere. Instead we suggest that it is directly related to discharges in the polar cap region of the pulsar.
Gongping Huang - One of the best experts on this subject based on the ideXlab platform.
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on the design of robust steerable frequency invariant beampatterns with concentric circular microphone arrays
International Conference on Acoustics Speech and Signal Processing, 2018Co-Authors: Gongping Huang, Jingdong Chen, Jacob BenestyAbstract:This paper studies the problem of frequency-invariant beamforming with concentric circular microphone arrays (CCMAs). We develop a beamforming algorithm based on an optimal approximation of the beamformer's beampattern with the Jacobi-Anger expansion. In comparison with the existing frequency-invariant beamformers with either circular microphone arrays (CMAs) or CCMAs, the developed algorithm offers the following advantages: 1) it can mitigate the deep-null problem encountered in CMAs and therefore has a consistent Directivity Factor over the frequency range of speech signals; 2) it is more flexible in terms of steering flexibility and the resulting beampattern can be steered to any direction; and 3) it does not require the microphones in different rings of the CCMA to be aligned, which is very useful in practice, particularly when microphone arrays with small and compact apertures have to be used.
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on the design of frequency invariant beampatterns with uniform circular microphone arrays
IEEE Transactions on Audio Speech and Language Processing, 2017Co-Authors: Gongping Huang, Jacob Benesty, Jingdong ChenAbstract:This paper deals with two critical issues about uniform circular arrays (UCAs): frequency-invariant response and steering flexibility. It focuses on some optimal design of frequency-invariant beampatterns in any desired direction along the sensor plane. The major contributions are as follows. 1) We explain how to include the steering information in the desired Directivity pattern. 2) We show that the optimal approximation of the beamformer's beampattern with a UCA from a least-squares error perspective is the Jacobi–Anger expansion. 3) We develop an approach to the design of any desired symmetric Directivity pattern, where the deduced beampattern is almost frequency invariant and its main beam can be pointed to any wanted direction in the sensor plane. 4) With the proposed approach, we derive an explicit form of the white noise gain (WNG) and the Directivity Factor (DF), and explain clearly the white noise amplification problem at low frequencies and the DF degradation at high frequencies. The analysis also indicates that increasing the number of microphones can always improve the WNG. We show that the proposed method is a generalization of circular differential microphone arrays. The relationship between the proposed method and the so-called circular harmonics beamformers is also discussed.
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Subspace superdirective beamformers based on joint diagonalization
2016 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2016Co-Authors: Changlei Li, Gongping Huang, Jacob Benesty, Jingdong ChenAbstract:Although they have been intensively studied and used in many applications due to their high Directivity Factor (DF), superdirective beamformers are sensitive to sensor noise and mismatch between sensors. This paper studies the problem of superdirective beamforming combined with the joint diagonalization method. We develop a subspace superdirective beamforming approach, which can achieve a good compromise between a high DF and white noise amplification. Simulations are performed to justify our theoretical analysis and demonstrate the good properties of this subspace superdirective beamforming approach.
V A Soglasnov - One of the best experts on this subject based on the ideXlab platform.
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giant pulses from psr b1937 21 with widths 15 nanoseconds and tb 5 1039 k the highest brightness temperature observed in the universe
The Astrophysical Journal, 2004Co-Authors: V A Soglasnov, M V Popov, N Bartel, W H Cannon, Yu A Novikov, V I Kondratiev, V I AltuninAbstract:Giant radio pulses of the millisecond pulsar B1937+21 were recorded with the S2 VLBI system at 1.65 GHz with NASA/JPL's 70 m radio telescope at Tidbinbilla, Australia. These pulses have been observed as strong as 65,000 Jy with widths ≤15 ns, corresponding to a brightness temperature of Tb ≥ 5 × 1039 K, the highest observed in the universe. The vast majority of these pulses occur in 5.8 and 8.2 μs windows at the very trailing edges of the regular main pulse and interpulse profiles, respectively. Giant pulses occur, in general, with a single spike. Only in one case of 309 was the structure clearly more complex. The cumulative distribution is fitted by a power law with index -1.40 ± 0.01 with a low-energy but no high-energy cutoff. We estimate that giant pulses occur frequently but are only rarely detected. When corrected for the Directivity Factor, 25 giant pulses are estimated to be generated in one neutron star revolution alone. The intensities of the giant pulses of the main pulses and interpulses are not correlated with each other nor with the intensities or energies of the main pulses and interpulses themselves. Their radiation energy density can exceed 300 times the plasma energy density at the surface of the neutron star and can even exceed the magnetic field energy density at that surface. We therefore do not think that the generation of giant pulses is linked to the plasma mechanisms in the magnetosphere. Instead we suggest that it is directly related to discharges in the polar cap region of the pulsar.
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giant pulses from psr b1937 21 with widths 5 x 10 39 k the highest brightness temperature observed in the universe
arXiv: Astrophysics, 2004Co-Authors: V A Soglasnov, M V Popov, N Bartel, W H Cannon, Yu A Novikov, V I Kondratiev, V I AltuninAbstract:Giant radio pulses of the millisecond pulsar B1937+21 were recorded with the S2 VLBI system at 1.65 GHz with NASA/JPL's 70-m radio telescope at Tidbinbilla, Australia. These pulses have been observed as strong as 65000 Jy with widths = 5 x 10^39 K, the highest observed in the universe. The vast majority of these pulses occur in a 5.8 mcs and 8.2 mcs window at the very trailing edges of the regular main pulse and interpulse profiles, respectively. Giant pulses occur in general with a single spike. Only in one case out of 309 was the structure clearly more complex. The cumulative distribution is fit by a power law with index -1.40 +/- 0.01 with a low-energy but no high-energy cutoff. We estimate that giant pulses occur frequently but are only rarely detected. When corrected for the Directivity Factor, 25 giant pulses are estimated to be generated in one neutron star revolution alone. The intensities of the giant pulses of the main pulses and interpulses are not correlated with each other nor with the intensities or energies of the main pulses and interpulses themselves. Their radiation energy density can exceed 300 times the plasma energy density at the surface of the neutron star and can even exceed the magnetic field energy density at that surface. We therefore do not think that the generation of giant pulses is linked to the plasma mechanisms in the magnetosphere. Instead we suggest that it is directly related to discharges in the polar cap region of the pulsar.