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This paper presents a fast and compressible multiple signal classification algorithm (C-MUSIC) based on the manifold separation technique (MST) for a uniform circular array (UCA), named as MC-MUSIC. Making use of the MST, the steering vector (SV) of the UCA can be converted into a new SV, which has a Vandermonde structure similar to a uniform linear array. Then a noise-like subspace cluster (NLSC) can be generated by applying a new linear relation between the true direction-of-arrival (DOA) and virtual DOA to the new given SV. Finally, the angular field-of-view can be compressed to a small sector by the intersection of the NLSC so that the calculation times of the spatial spectrum can be reduced effectively. Simulations demonstrate the presented method can maintain the high precision of the DOA estimation with low computational complexity. [ABSTRACT FROM AUTHOR]

In array signal processing, Estimating the quantity of signal sources represents a crucial area of investigation. In this paper, a comprehensive introduction and analysis of the estimation methods for determining the number of signal sources are presented, including the background and significance, and the significance of precise estimation of the quantity of signal sources. The influence of factors such as signal-to-noise ratio (SNR), noise background, and number of snapshots on the estimation algorithm is discussed in detail. At the same time, common array models are introduced. Then, different signal source number estimation algorithms are analyzed in detail, and their respective advantages and applicable conditions are pointed out. Finally, the performance of each algorithm in different situations is evaluated by comparing the performance of the algorithms under different SNRs, snapshot numbers, and array elements. The experimental results show that with the increase of the SNR and the number of array elements, the correct estimation probability of the algorithm also increases correspondingly, which provides a reliable experimental basis and performance evaluation for the estimation. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian Polytechnic University is the property of Journal of Dalian Polytechnic University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

UAV communications have seen a rapid rise in the last few years. The drone class of UAV has particularly become more widespread around the world, and illicit behavior using drones has become a problem. Therefore, localization, tracking, and even taking control of drones have also gained interest. Knowing the frequency of a target signal, its position can be determined (as the angle of arrival with respect to a fixed receiver point) using radio frequency-based localization techniques. One such technique is represented by the subspace-based algorithms that offer highly accurate results. This paper presents the implementation of the MUSIC algorithm on an SDR-based system using a uniform circular antenna array and its experimental evaluation in relevant outdoor environments for drone localization. The results show the capability of the system to indicate the AoA of the target signal. The results are compared with the actual direction computed from the log files of the drone application and validated with a professional direction-finding solution (i.e., Narda SignalShark equipped with the automatic direction-finding antenna). [ABSTRACT FROM AUTHOR]

Aiming at the problem that the coherent signal cannot be estimated when the traditional UCA-RB-MUSIC algorithm is used to detect the partial discharge of the transformer, an improved UCA-RB-MUSIC algorithm is suggested to reconstruct the signals captured by the array so that the number of calls sources is equivalent to the rank of the reconstructed signal matrix. The impact of correlated signals is eradicated. The results of simulation analysis and experimental verification show that when the improved UCA-RB-MUSIC algorithm is used to locate a single and double partial discharge source, the improved positioning error is only half of the mistake before improvement, which enhances the accuracy and resolution of uniform circular array positioning and the accuracy of transformer partial discharge detection.

The channel matrix of the commonly used uniform circular array-based orbital angular momentum (UCA-OAM) system reaches the full-rank state when the degree of freedom (DoF) is limited only by the number of UCA antenna elements. The rank of the channel matrix of the UCA-OAM system is equal to DoF under this condition. However, the practical DoF of the UCA-OAM system is always affected by other transmission factors, such as the transmission distance and the radius of the receiving antenna. Therefore, by exploiting the practical DoF of the UCA-OAM system affected by the transmission distance and the radii of the receiving antenna and transmission antenna, a novel channel capacity model of the UCA-OAM communication system with a deficient-rank channel (DRC) matrix is first proposed. Moreover, the formulas of the channel matrix and channel capacity for the DRC matrix are analytically derived. The results of numerical simulations indicate that when the practical transmission factors including transmission distance and radii of the receiving antenna and transmission antenna are considered, the UCA-OAM communication system with the DRC matrix has less channel capacity than that with the full-rank channel (FRC) matrix. These simulated results provide helpful guidance on the practical application of the UCA-OAM communication system. [ABSTRACT FROM AUTHOR]

In order to solve the problem of direction finding of coherent signals for uniform circular array under the condition of underdetermination, a direction of arrival (DOA) estimation algorithm combining geometric sequence decomposition and sparse reconstruction was proposed.Geometric sequence decomposition was used to split coherent groups and estimate the actual direction vector of each coherent group, while sparse reconstruction was used to estimate DOA for each coherent group.Simulation results demonstrate that when the number of elements of the uniform circular array is M, compared with the existing algorithms, the maximum number of sources that can be estimated by the proposed algorithm is M(M-1).And when the number of sources is large, the success rate and accuracy of direction finding are better.In addition, the proposed algorithm can solve the “angle merger” problem, and has advantages in the direction finding tasks with very few snapshots.

The channel matrix of the commonly used uniform circular array-based orbital angular momentum (UCA-OAM) system reaches the full-rank state when the degree of freedom (DoF) is limited only by the number of UCA antenna elements. The rank of the channel matrix of the UCA-OAM system is equal to DoF under this condition. However, the practical DoF of the UCA-OAM system is always affected by other transmission factors, such as the transmission distance and the radius of the receiving antenna. Therefore, by exploiting the practical DoF of the UCA-OAM system affected by the transmission distance and the radii of the receiving antenna and transmission antenna, a novel channel capacity model of the UCA-OAM communication system with a deficient-rank channel (DRC) matrix is first proposed. Moreover, the formulas of the channel matrix and channel capacity for the DRC matrix are analytically derived. The results of numerical simulations indicate that when the practical transmission factors including transmission distance and radii of the receiving antenna and transmission antenna are considered, the UCA-OAM communication system with the DRC matrix has less channel capacity than that with the full-rank channel (FRC) matrix. These simulated results provide helpful guidance on the practical application of the UCA-OAM communication system.

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The safety valve is the core component of the pressure-relief protection device for pressure-bearing special equipment. When the safety valve leaks, the medium of the pressure vessel will be lost and wasted, which may cause safety accidents. With the aim to solve the problem of accurately locating the multiple leakage sources of safety valves, a localization method combining a uniform circular array acoustic emission detection and an improved multiple signal classification (MUSIC) algorithm is proposed. First, an improved wavelet threshold function denoising method is introduced to extract acoustic emission signals with high SNR, thereby reducing the rank of the covariance matrix, weakening the noise dispersion caused by eigenvalue reconstruction, avoiding signal and noise cross-confusion, and improving positioning accuracy. By introducing a windowed fast Fourier transform (FFT) frequency division processing link to obtain narrowband signal, the premise of using MUSIC positioning algorithm is established. In addition, a forward/backward spatial smoothing algorithm is introduced in the decoherence link to reduce co-channel interference, reduce the rank loss of the signal covariance matrix, and improve the positioning accuracy of the algorithm. The results show that when the working pressure is 0.70 MPa, 0.75 MPa, and 0.80 MPa, the deviation between the azimuth angle and elevation angle positioning results of each leakage source obtained by the improved MUSIC algorithm and the actual angle does not exceed 2°, and the relative error does not exceed 3.5%. Therefore, the improved MUSIC algorithm can accurately locate multiple leakage sources of the safety valve, and as the working pressure of the safety valve increases, the positioning accuracy of the improved MUSIC algorithm also increases accordingly. [ABSTRACT FROM AUTHOR]

This paper presents the generation of orbital angular momentum (OAM) vortex waves with mode +1 using dielectric resonator antenna (DRA) array. The proposed antenna was designed and fabricated using FR-4 substrate to generate OAM mode +1 at 3.56 GHz (5G new radio band). The proposed antenna consists of 2 × 2 rectangular DRA array, a feeding network, and four cross slots etched on the ground plane. The proposed antenna succeeded in generating OAM waves; this was confirmed by the measured radiation pattern (2D polar form), simulated phase distribution, and intensity distribution. Moreover, mode purity analysis was carried out to verify the generation of OAM mode +1, and the purity obtained was 53.87%. The antenna operates from 3.2 to 3.66 GHz with a maximum gain of 7.3 dBi. Compared with previous designs, this proposed antenna is low-profile and easy to fabricate. In addition, the proposed antenna has a compact structure, wide bandwidth, high gain, and low losses, thus meeting the requirements of 5G NR applications. [ABSTRACT FROM AUTHOR]

In the direction-of-arrival (DOA) estimation methods for uniform circular arrays (UCAs) with directional sensors, the high computational complexity arises when achieving the estimation accuracy by leveraging all the sensors in the element space. We present a low-complexity sectorized DOA estimation scheme for directional UCAs. It models the radiation pattern within half-power bandwidth in a closed mathematical expression and thereby constructs reconfigurable sectorized steering vectors of an arbitrary angular sector by using the Hadamard cyclic vector with the Vandermonde structure. The DOA estimation over the azimuth plane throughout the element space is transformed to DOA estimates within multiple individual angular sectors. The new scheme comprises three stages, i.e., submatrix extraction, sectorized weighted beamforming and sector DOA estimation. The feasibility and effectiveness of the proposed scheme are validated by numerical simulations. The simulation results demonstrate that, compared to the previous sector-free DOA estimation methods based on the entire azimuth plane, our scheme has a low hardware and computational complexity under an acceptable estimation error. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Data Acquisition & Processing / Shu Ju Cai Ji Yu Chu Li is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A reconfigurable ultra-wideband multimode terahertz OAM antenna array based on graphene and vanadium dioxide (VO 2) is presented in this paper. The uniform circular array (UCA) composed of circularly polarized (CP) antennas, which include a ring radiation patch, a parasitic patch, a perovskite substrate and an irregular VO 2 ground plane. The radiation patch is covered with a layer of graphene, by changing the chemical potential of graphene, the working bandwidth and axial ratio bandwidth of the antenna can be changed. By changing the phase state of VO 2 (metal state / insulation state) to control the working state of the antenna. The impedance bandwidth (IBW) of the CP antenna proposed is 115.09% (1.73–6.42 THz), the axial ratio bandwidth (ARBW) is 43.97% (2.36–3.69 THz). Using the CP antenna unit can simplify the complex feed network, and only feeding the equal amplitude and equal phase excitation can realize the vortex wave. Changing the number and rotation angle of the antenna unit can realize multimode vortex waves with the l = 0, ±1, ±2, ±3, the purity is approximately 1, respectively. The proposed UCA has excellent application prospect in the 6G communication. [ABSTRACT FROM AUTHOR]

In order to solve the problem of direction finding of coherent signals for uniform circular array under the condition of underdetermination, a direction of arrival (DOA) estimation algorithm combining geometric sequence decomposition and sparse reconstruction was proposed. Geometric sequence decomposition was used to split coherent groups and estimate the actual direction vector of each coherent group, while sparse reconstruction was used to estimate DOA for each coherent group. Simulation results demonstrate that when the number of elements of the uniform circular array is M, compared with the existing algorithms, the maximum number of sources that can be estimated by the proposed algorithm is M(M--1). And when the number of sources is large, the success rate and accuracy of direction finding are better. In addition, the proposed algorithm can solve the "angle merger" problem, and has advantages in the direction finding tasks with very few snapshots. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of random array deformations on Direction-of-Arrival (DOA) estimation with root-Multiple Signal Classification for uniform circular arrays (UCA root-MUSIC) are characterized by a conformally mapped generalized Polynomial Chaos (gPC) algorithm. The studied random deformations of the array are elliptical and are described by different Beta distributions. To successfully capture the erratic deviations in DOA estimates that occur at larger deformations, specifically at the edges of the distributions, a novel conformal map is introduced, based on the hyperbolic tangent function. The application of this new map is compared to regular gPC and Monte Carlo sampling as a reference. A significant increase in convergence rate is observed. The numerical experiments show that the UCA root-MUSIC algorithm is robust to the considered array deformations, since the resulting errors on the DOA estimates are limited to only 2 to 3 degrees in most cases. [ABSTRACT FROM AUTHOR]

The inspection of wellbore casings has been extensively investigated owing to the increasing concern for safety in oil and gas production. However, efficient techniques for inspecting asymmetry defects have not been achieved. In this study, we developed a uniform circular array (UCA) to address the problem of borehole pulsed eddy current (PEC) techniques for asymmetry defect inspection in downhole casings. Based on the borehole PEC system model, the UCA developed with multiple independent probes was designed to achieve asymmetry defect inspection, and the three-dimensional magnetic field data of borehole depths, circumferential azimuths, and sampling times could be obtained. Furthermore, a multichannel data acquisition circuit, which guarantees downhole operation at 150 °C, was developed for the synthesized UCA. Using azimuth dimension information from the synthesized UCA at a certain borehole depth, we obtained an inspection approach for the width and penetration depth of asymmetry defects in the circumferential and radial directions, respectively. Simulations and field experiments were conducted, and the results demonstrate the effectiveness of the proposed method in inspecting asymmetry defects. [ABSTRACT FROM AUTHOR]

To improve the computation and real-time performances of the multiple signal classification (MUSIC) algorithm in 3D space, a fast sound source localization method based on the bat algorithm (BA) and the 3D-MUSIC, called BA-based 3D-MUSIC algorithm (3D-BMUSIC), is presented in this paper. 3D-BMUSIC greatly reduces the computation load by replacing the regular grid search with the BA. First, the near-field spherical wave model is established to obtain the spectral function of the 3D-MUSIC. Then, the spectral function is defined as the fitness function, which calculates the fitness value corresponding to each bat position. Finally, the global optimal bat position with the largest fitness value, as sound source localization, is obtained by successive iteration and sorting. The simulation and experiment show that 3D-BMUSIC accurately estimates the DOA and distance of near-field sources, and the root-mean-square error (RMSE) of 3D-BMUSIC is less than that of 3D-MUSIC. In addition, 3D-BMUSIC effectively reduces the computation time by approximately 96–98%. With shorter computation time and higher efficiency, 3D-BMUSIC promotes hardware implementation and is more suitable for high-precision localization of near-field sound sources. [ABSTRACT FROM AUTHOR]

In this paper, we study the two-dimensional direction of arrival (2D-DOA) estimation problem in a switching uniform circular array (SUCA), which means performing 2D-DOA estimation with a reduction in the number of radio frequency (RF) chains. We propose a covariance matrix completion algorithm for 2D-DOA estimation in a SUCA. The proposed algorithm estimates the complete covariance matrix of a fully sampled UCA (FUCA) from the sample covariance matrix of the SUCA through a neural network. Afterwards, the MUSIC algorithm is performed for 2D-DOA estimation with the completed covariance matrix. We conduct Monte Carlo simulations to evaluate the performance of the proposed algorithm in various scenarios; the performance of 2D-DOA estimation in the SUCA gradually approaches that in the FUCA as the SNR or the number of snapshots increases, which means that the advantages of a FUCA can be preserved with fewer RF chains. In addition, the proposed algorithm is able to implement underdetermined 2D-DOA estimation. [ABSTRACT FROM AUTHOR]

This paper addresses the two-dimensional (2D) direction-of-arrival (DOA) estimation issue for signals with known waveforms but unknown amplitudes using uniform circular array (UCA). Unlike maximum likelihood (ML) methods such as decoupled maximum likelihood (DEML), parallel decomposition (PADEC) and so forth, which estimate DOA by spectrum peak search, we propose an efficient interferometer-based method with known waveforms. The proposed method first estimates spatial signature matrix based on ML method whose each column contains 2D DOA information corresponding to a source. Then, an interferometer procedure is performed to obtain 2D DOA estimate of each source from a closed-form solution separately and in parallel. Several simulation results show that the proposed method can achieve a significantly improvement in performance that coincides with the ML method as well as Cramér-Rao Bound (CRB), especially under some poor conditions, such as low SNR, fewer sensors or small snapshots. In addition, the performance will not degrade as the number of sources increases if the source signals are uncorrelated with each other. Meanwhile, it reduces a great amount of computational complexity without loss of too much accuracy. Thus, the proposed method is quite suitable for 2D DOA estimation with known waveforms in practice. [ABSTRACT FROM AUTHOR]

The uniform circular array (UCA) has been considered to be an effective way to generate orbital angular momentum (OAM) waves. However, by using UCA to transmit multiplexing OAM signals, the peak-to-average power ratio (PAPR) is unavoidable, which brings the low efficiency to the power amplification. In this letter, the interferometry code is introduced to reduce the PAPR in the antenna element of OAM multiplexing transmission at the transmitter. Specifically, the system architecture of OAM by UCA is proposed with the interferometry code spread for PAPR reduction. The simulations and experiments confirm the validity and efficiency of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents the generation of orbital angular momentum (OAM) vortex waves with mode +1 using dielectric resonator antenna (DRA) array. The proposed antenna was designed and fabricated using FR-4 substrate to generate OAM mode +1 at 3.56 GHz (5G new radio band). The proposed antenna consists of 2 × 2 rectangular DRA array, a feeding network, and four cross slots etched on the ground plane. The proposed antenna succeeded in generating OAM waves; this was confirmed by the measured radiation pattern (2D polar form), simulated phase distribution, and intensity distribution. Moreover, mode purity analysis was carried out to verify the generation of OAM mode +1, and the purity obtained was 53.87%. The antenna operates from 3.2 to 3.66 GHz with a maximum gain of 7.3 dBi. Compared with previous designs, this proposed antenna is low-profile and easy to fabricate. In addition, the proposed antenna has a compact structure, wide bandwidth, high gain, and low losses, thus meeting the requirements of 5G NR applications.

This paper addresses the two-dimensional (2D) direction-of-arrival (DOA) estimation issue for signals with known waveforms but unknown amplitudes using uniform circular array (UCA). Unlike maximum likelihood (ML) methods such as decoupled maximum likelihood (DEML), parallel decomposition (PADEC) and so forth, which estimate DOA by spectrum peak search, we propose an efficient interferometer-based method with known waveforms. The proposed method first estimates spatial signature matrix based on ML method whose each column contains 2D DOA information corresponding to a source. Then, an interferometer procedure is performed to obtain 2D DOA estimate of each source from a closed-form solution separately and in parallel. Several simulation results show that the proposed method can achieve a significantly improvement in performance that coincides with the ML method as well as Cramér-Rao Bound (CRB), especially under some poor conditions, such as low SNR, fewer sensors or small snapshots. In addition, the performance will not degrade as the number of sources increases if the source signals are uncorrelated with each other. Meanwhile, it reduces a great amount of computational complexity without loss of too much accuracy. Thus, the proposed method is quite suitable for 2D DOA estimation with known waveforms in practice.

The theory of multiplexing electromagnetic signals by means of twisted photons generated by a uniform circular array (UCA) is developed in the case when the receiving antenna represents an array of elements located on a circular arc. The radiating elements are characterized by certain current distributions and are not points, in general. The polarization of created electromagnetic waves is fully taken into account. The notion of discrete twisted photons of the order N is introduced and orthogonality of these modes modulo N is established. Both paraxial and planar discrete twisted photons are considered. The explicit expressions for the signals received are obtained. It is shown that, in the simplest scenario, a K times decrease of the circular arc where the receiving array antenna is placed results in a K times decrease of the number of independent information channels. In the more sophisticated approach, one can restore all N ≫ 1 independent information channels in receiving the signal by an array antenna with N elements located on a circular arc with the central angle 2 π / K. However, this problem becomes rapidly ill-conditioned as one increases K. The method mitigating this issue is described. The estimates for the corresponding condition numbers are found. The scenario with beam steering, where the radiation produced by the UCA is concentrated near the receiving circular arc array antenna, is also investigated. The orthogonality of the information channels is proved in this case and the corresponding transformation matrix and its condition number are found. • Multiplexing signals with twisted photons by circular arc phased arrays is elaborated. • Explicit expressions for the signals received by antennas are obtained. • Asymptotics of singular values of the Vandermonde matrix is found. • Multiplexing by OAM combined with beam steering is investigated. [ABSTRACT FROM AUTHOR]

Fourth-order cumulant is one of most widely used high-order cumulant for direction of arrival (DOA) estimation due to its ability of expanding the virtual array aperture as well as suppressing Gaussian noise. To address the two-dimensional (2D) DOA estimation problem, we propose a modified MUSIC scheme for uniform circular array (UCA) in this paper. Firstly, the fourth-order cumulant of UCA is considered to construct a new propagator, resulting in the elimination of a priori knowledge of the number of signals. Secondly, the UCA is transformed by beamspace transformation, reducing the time computational complexity of the algorithm since the two-dimensional grid search and singular value decomposition are avoided. And finally a low-rank recovery algorithm is adopted to improve the accuracy regarding the limited snapshots scenario. The numerical simulations validate the superiority of the proposed method. [ABSTRACT FROM AUTHOR]