Joint Azimuth Research Articles

Wideband radar echo cancellation based on joint azimuth interrupted-sampling and frequency modulation

Wideband radar echo cancellation based on joint azimuth interrupted-sampling and frequency modulation

Joint Azimuth, Elevation and Delay Estimation for Single Base Station Localization in 3D IIoT

Integrated sensing and communication (ISAC) in the Industrial Internet of Things (IIoT) presents unique challenges in terms of localization techniques. While three-dimensional (3D) environments offer extra challenges to enhanced accuracy and realism, research in this area remains limited. To bridge this gap, we propose a novel localization technique assisted by a single base station (BS) in 3D IIoT scenarios. Our approach employs the MUltiple SIgnal Classification (MUSIC) algorithm to jointly estimate the angle of arrival (AoA) in azimuth and elevation, as well as the time of arrival (ToA). Compared to conventional multi-BS-assisted or MUSIC-based algorithms, our technique offers flexibility, easy implementation, and low computational cost. To improve performance, we integrate the Taylor-series into the iterative process after a MUSIC-based joint azimuth, elevation angle and delay estimation (JAEDE), resulting in a significant 99% reduction in computational complexity compared to a two-step MUSIC-based approach utilizing coarse-fine grid searching. Through numerical simulations, we compare our algorithm with three other MUSIC-based joint or separate estimation approaches, demonstrating its superior performance in azimuth angle of arrival (AoAz), elevation angle of arrival (AoAe), TOA, and overall location estimation across varying signal-to-noise ratio (SNR) conditions.

Beamspace Joint Azimuth, Elevation, and Delay Estimation for Large-Scale MIMO-OFDM System

Beamspace Joint Azimuth, Elevation, and Delay Estimation for Large-Scale MIMO-OFDM System

Fusion-based high-quality polarization 3D reconstruction

The fusion of shape from polarization (SFP) and depth sensors is an effective method for high-quality 3D reconstruction. However, accurate registration of images from different sensors is a difficult problem. In this paper, we propose a 3D reconstruction method based on the fusion of SFP and polarization-modulated ranging (PMR) for the first time, where only a single image sensor is utilized to acquire both polarized images and depth data. Therefore, the challenging image registration problem can be avoided. This method is based on the following observation: SFP can retrieve inaccurate objects’ 3D shapes with fine textures, whereas PMR can provide coarse but accurate absolute depths, resulting in a good necessity of fusing these two modalities. To this end, we propose two fusion models: a joint azimuth estimation model to obtain a fused azimuth angle with π−ambiguity corrected, and a joint zenith estimation model to estimate an accurate fused zenith angle. Finally, the reconstructed depth is integrated from the fused azimuth and zenith angles, which can provide accurate absolute depth with fine textures. Extensive experiments have been conducted to verify the efficiency of the proposed method over other state-of-the-art methods besides its robustness to the targets with different kinds of features, demonstrating its broad application prospects in 3D reconstruction.

Joint Estimation of Azimuth and Distance for Far-Field Multi Targets Based on Graph Signal Processing

Target position estimation is one of the important research directions in array signal processing. In recent years, the research of target azimuth estimation based on graph signal processing (GSP) has sprung up, which provides new ideas for the Direction of Arrival (DoA) application. In this article, by extending GSP-based DOA to joint azimuth and distance estimation and constructing a fully connected graph signal model, a multi-target joint azimuth and distance estimation method based on GSP is proposed. Firstly, the fully connection graph model is established related to the phase information of a linear array. For the fully connection graph, the Fourier transform method is used to solve the estimated response function, and the one-dimensional estimation of azimuth and distance is completed, respectively. Finally, the azimuth and distance estimation information are combined, and the false points in the merging process are removed by using CLEAN algorithm to complete the two-dimensional estimation of targets. The simulation results show that the proposed method has a smaller mean square error than the Multiple Signal Classification (MUSIC) algorithm in azimuth estimation under the condition of a low signal-to-noise ratio and more accurate response values than the MUSIC algorithm in distance estimation under any signal-to-noise ratio in multi-target estimation.

Three-Dimensional InISAR Imaging of Maneuvering Targets With Joint Motion Compensation and Azimuth Scaling Under Single Baseline Configuration

Three-Dimensional InISAR Imaging of Maneuvering Targets With Joint Motion Compensation and Azimuth Scaling Under Single Baseline Configuration

Transform Domain: Design of Closed-Form Joint 2-D DOA Estimation Based on QR Decomposition

As an alternative to existing methods, we design a transform-domain algorithm to avoid the computational cost of a two-dimensional (2-D) spectral peak search when addressing the problem of joint azimuth and elevation directions-of-arrival (DOAs) estimation via an L-shaped array. Motivated by the linear prediction property of the signal cross-covariance matrix, the 2-D DOA estimation problem is equivalently converted into a 2-D frequency estimation problem. With the QR decomposition technique, the closed-form solutions in the transform domain with respect to the azimuth and elevation angles are successively estimated using the weighted least squared method as the solver, and it is shown that the proposed scheme achieves automatically pairing while permitting fast implementation. Simulations are presented to verify the effectiveness of the proposed method by comparison with several 2-D DOA estimators as well as the Cramer–Rao lower bound.

Joint Azimuth, Elevation, and Delay Estimation for 3-D Indoor Localization

Accurate localization in harsh indoor environments has long been a challenging problem due to the presence of multipath. Since joint direction-of-arrival (DOA) and time delay (TD) estimation has the capability to separate the line-of-sight signal from multipath signals in the TD space, it has recently become a key technique for accurate indoor localization in next-generation WiFi and 5G networks. This paper addresses the problem of joint azimuth, elevation, and TD estimation of multiple reflections of a known signal. First, we propose an efficient approximate maximum likelihood algorithm for this problem, which updates the DOA and TD parameters alternatingly. This algorithm applies to arbitrarily distributed (planar or 3-D) arrays. Then, we present the closed-form Cramer–Rao bound for joint DOA and TD estimation, based on which we provide further analysis to show the benefit of joint DOA and TD estimation over DOA-only estimation. Although the benefit of joint estimation has been empirically shown long ago, our analysis is the first theoretical proof of it. Finally, simulation results have been provided to demonstrate the theoretical finding and the effectiveness of the new algorithm. Matlab code for the new algorithm is available at https://github.com/FWen/JADE.git .

Joint Estimation of Azimuth and Elevation via Manifold Separation for Arbitrary Array Structures

Direction-of-arrival estimation is a ubiquitous task in array processing. The conventional MUltiple SIgnal Classification (MUSIC) method is often computationally expensive, particularly in the application of joint azimuth and elevation estimation. In this paper, we propose an efficient way to compute the two-dimentional (2D) spatial spectrum. By using the manifold separation technique, we find that the 2-D null-spectrum has the form of discrete Fourier transform (DFT). Moreover, the coefficients of the DFT form can be truncated and computed in parallel. Then by exploiting the fact that the nonzero coefficients are concentrated only at the top-left corner, we present a partial 2-D DFT to compute the 2-D spatial spectrum, which can reduce the latency significantly. In order to improve the estimation performance, we formulate an iterative multidimensional-subspace-fitting estimator in which we apply the first-order Taylor expansion to expand the projection operator. At each iteration, the estimation errors can be computed by solving a set of linear equations. Numerical results demonstrate that the proposed estimator offers better estimation performance compared with the classical 2-D MUSIC.

Estimation 2-D angle of arrival with a cross-correlation matrix

A new approach to high-resolution estimation of two-dimensional direction-of-arrival of multiple far-field narrowband signals for an L-shaped array is presented in this article. By making full use of the L-shaped array geometry and the cross-correlation matrix, the proposed method only needs one-dimensional estimation for joint azimuth and elevation angle estimation. The azimuth and elevation angles estimated by the proposed method can pair automatically. The effectiveness of the proposed method is verified through computer simulations, and it is shown that the proposed method performs well in the situation of low SNR and small angular separation.

Joint Azimuth and Elevation Angle Estimation Using Incomplete Data Generated by a Faculty Antenna Array

Joint Azimuth and Elevation Angle Estimation Using Incomplete Data Generated by a Faculty Antenna Array

A Comment on “Joint elevation and Azimuth direction finding using L-shaped array”

A recent method proposed by J. Liang and D. Liu in “Joint elevation and Azimuth direction finding using L-shaped array,” IEEE Trans. Antennas Propag. vol. 58, no. 6, pp. 2136-2141, Jun., 2010, has a constraint that it cannot resolve the sources which share the same joint electric angle: θ = Φ - γ. This comment proposes a solution to this constraint and validates the concept through a simulation example.

FAST 2-D DOA AND POLARIZATION ESTIMATION USING ARBITRARY CONFORMAL ANTENNA ARRAY

A fast and simple parameter estimation algorithm, joint azimuth angles, elevation angles and polarization parameters of incident sources for an arbitrary conformal array is proposed. Based on 2-D Discrete Fourier Transform (2-D DFT), the computational complexity can be reduced signiflcantly compared with traditional 2- D space-search MUSIC or polynomial rooting (search-free) methods. The antenna elements can be mounted on arbitrary curved surfaces or platforms. Conformal array characteristics, such as directional radiation patterns of the elements and polarization are taken into consideration. Numerical simulations based on real-world conformal arrays are provided to demonstrate the performance of the proposed method.

Orocline timing through joint analysis: Insights from the Ibero-Armorican Arc

The timing and kinematics of oroclinal bending in the core of the Ibero-Armorican Arc (IAA) has recently been constrained using paleomagnetic data from the Cantabrian Zone in northern Iberia. This study analyzes the joint-patterns present in rock units deposited pre-, syn- and post-oroclinal bending. Systematic changes in the orientations of tensional joint-sets in superimposed stratigraphic units are interpreted to record the progressive stages of oroclinal bending in the core of the IAA. Time constrains for joint set development are constrained by the known ages of the bounding unconformities that limit the studied stratigraphic units. Joint azimuth variability in the pre-orocline rocks (Neoproterozoic to pre-Upper Carboniferous) is comparable to the present arc curvature of the orocline (about 180°); the joints in the syn-orocline rocks (Upper Pennsylvanian or Stephanian, 304 to 299 Ma) show a lower azimuthal variability that is comparable to about 50–70% of the total curvature seen in pre-orocline rocks. Finally, post-orocline rocks (Permian) contain joints that have uniform azimuths for each set across the entirety of the present-day arc. Together these spatially and temporally distinct joint sets suggest that rotations in the Cantabrian Zone took place in the Upper Pennsylvanian during a ca. 10 Ma time period, which agrees well with previous paleomagnetic arguments. The data also provides supporting evidence for oroclinal bending by rotation around vertical axes of an initially linear, or nearly linear, orogenic belt. And finally, these data highlight the potential power in using tectonic joint sets for constraining thrust belt kinematics in curved orogenic systems when unconformity bounded stratigraphic sequences are present that are coeval with orocline development.

Numerical Analysis on Failure Mechanism of Intermittent Joints

The mechanical characteristics of jointed rocks are mainly controlled by geometrical features of intermittent joints. The failure mechanism and shear behavior of discontinuous joints are simulated by series of direct shear tests using the particle flow code (PFC2D). The effects of joint persistence, separation and azimuth angle on the failure strength of jointed rock are studied in detail. The results shows that peak shear strength can be considered as a function of the geometrical parameters, which is in a reasonable accordance with other experimental results. Meanwhile, as for failure mechanism, joint separation and azimuth angle are especially discussed, and specific damage patterns are presented as well.

Joint Azimuth and Elevation Direction Finding Using Cumulant

Two-dimensional (2-D) directions-of-arrival (DOA) estimation is a key problem in array signal processing fields. To save hardware costs and avoid multidimensional search, Liu proposed an ESPRIT-like algorithm using cumulant. However, this algorithm still have non neglible drawbacks: (1) suffering losses of the array aperture and resultant fewer sources to be processed from an array of given sensor number; (2) having an estimation failure problem when elevation angles are between 70deg and 90deg in typical mobile communication; and (3) requiring pairing parameters. To overcome these problems, this paper develops a new cumulant-based algorithm. The main contributions of this paper are three-fold: (1) designing a special volume array to avoid the estimation failure problem; (2) constructing three cumulant matrices using the fourth-order cumulants of some properly chosen array outputs to increase the array aperture; and (3) forming a parallel factor (PARAFAC) model of cumulant matrices in the cumulant domain to avoid pairing parameters. Simulation results are presented to validate the performance of the proposed method.

Detailed characterisation of an indoor MIMO channel in the double directional spatial domain

The spatial domain characteristics of an indoor multiple-input multiple-output (MIMO) communication system are examined in detail. Using a high-resolution algorithm, the authors were able to effectively estimate multipath parameters on the joint azimuth of arrival/azimuth of departure (AoA/AoD) domain. The analysis showed dense clustering phenomena at the vast majority of considered locations and a strong correlation between the azimuth spreads of the two angular domains with the presence of line-of-sight (Los) specular components or when the distance between the transmitter (Tx) and the receiver (Rx) is low. The authors also noticed higher azimuth dispersions, compared with those reported in the literature, which can be attributed to low antenna heights and local scattering interactions in the vicinity of both the transmit and receive arrays. Finally, the impact of the spatial global parameters on the ergodic MIMO capacity was tested revealing a direct relation between them.

Joint azimuth, elevation, and time of arrival estimation of diffuse sources

In this paper, we estimate the azimuth, the elevation, and the time of arrival of diffuse sources using the covariance matching estimator (COMET) algorithm. Previous works dealt with azimuth estimation of diffuse sources or azimuth and time of arrival estimation of point sources. However, in realistic situations, a tridimensional diffuse source localization is needed, which is the main objective of this paper. We show that the dimensionality of the COMET algorithm can be reduced by separating the estimation of the different source powers and the noise variance from that of the remaining parameters, namely the azimuth, the elevation, the time of arrival, and the corresponding angular and temporal spreads. As COMET still involves a multidimensional nonlinear optimization, we choose, in this purpose, the alternating projection algorithm to alleviate the corresponding complexity. The multiple signal classification (MUSIC) algorithm is processed to initialize the so-resulted algorithm. Simulations of the proposed algorithm are carried in different contexts and compared to the Cramer-Rao Bound, MUSIC algorithm, and dispersed signal parametric estimation simulation results.

Azimuth and elevation estimation for noncircular signals

A novel 2D direction-finding algorithm for noncircular signals using two parallel linear arrays, called the extended rank reduction (ERARE) algorithm, is presented. The method needs only 1D search for joint azimuth and elevation estimation. The azimuth and elevation angles estimated by ERARE are paired automatically.

Numerical study of shear behavior of intermittent rock joints with different geometrical parameters

The purpose of this paper is to investigate shear behavior of rock specimens containing several intermittent joints with different geometrical parameters. Through three series of direct shear tests based on rock failure process analysis (RFPA 2D) code, the whole shear failure process is visually observed and the failure patterns in reasonable accordance with other experimental results are obtained. In general, the failure pattern is mostly influenced by the geometrical parameters of rock joints while shear strength is closely related to the failure pattern and its failure mechanism. It is observed that the propagation of wing cracks depends on the joint separation and the joint azimuth angle, and the connection of wing cracks dominates the eventual failure pattern and determines the peak shear load of the rock specimens. The results also show that macro shear fracture is due to the mesoscopic tensile damage of a large number of elements. This numerical study has made a more reasonable theoretical explanation for the shear mechanism of jointed rock due to the inner damages that are difficult to observe in an experimental testing.