Array Radar Research Articles

SuperDARN Radar Wind Observations of Eastward-Propagating Planetary Waves

An array of SuperDARN meteor radars at northern high latitudes was used to investigate the sources and characteristics of eastward-propagating planetary waves (EPWs) at 95 km, with a focus on wintertime. The nine radars provided the daily mean meridional winds and their anomalies over 180 degrees of longitude, and these anomalies were separated into eastward and westward waves using a fast Fourier transform (FFT) method to extract the planetary wave components of zonal wavenumbers 1 and 2. Years when a sudden stratospheric warming event with an elevated stratopause (ES-SSW) occurred during the winter were contrasted with years without such events and composited through superposed epoch analysis. The results show that EPWs are a ubiquitous—and unexpected—feature of meridional wind variability near 95 km. Present even in non-ES-SSW years, they display a regular annual cycle peaking in January or February, depending on the zonal wavenumber. In years when an ES-SSW occurred, the EPWs were highly variable but enhanced before and after the onset.

A radar array expansion design method based on modular subarray layout

Abstract This paper introduces a design method for expandable subarray structures used in phased array radar arrays. Based on the structural characteristics of modular subarray layout for large radar arrays, this paper analyzes the assembly dimension chain tolerance based on subarray expansion. One third of the allowable deviation of the radar array is used as the subarray design tolerance, and the size tolerance of each installation surface of the subarray is designed according to the design tolerance. Finally, the subarray array is assembled into any size of radar array, and the probability of the radar array assembly accuracy meeting the allowable deviation is 99.73%. For large radar arrays, adopting this design method can significantly reduce the tolerance span between the sub array and the area array, greatly reducing the difficulty of design and processing. This paper provides a fundamental design method for the expansion design of radar arrays with similar systems, which has universal applicability.

Generalized sidelobe canceller based adaptive multiple-input multiple-output radar array beamforming under scenario mismatches

It is well known that the performance of an adaptive MIMO radar array fully depends on the precise steering control and is deteriorated by even a small scenario mismatch. This paper presents an advanced generalized sidelobe canceller (AGSC) based adaptive MIMO radar array beamformer with robustness against the effect due to scenario mismatches. A new signal blocking matrix is developed for effectively blocking the desired signal when the adaptive beamforming is performed under multiple scenario mismatches. The novelty of the new signal blocking matrix is that it contains two additional matrix components in addition to the conventional blocking matrix. The first one is a matrix made up of the basis orthogonal to some appropriately designed derivative constraint vector. It avoids the possible leakage of the desired signal due to scenario mismatches. The other one is a matrix made up of the dominant eigenvectors associated with the correlation matrix of the blocked data vector at the output of the first matrix component. It is employed to preserve all of the interference signals. As a result, the whole blocking operation can delete the desired signal and save the interference signals under multiple scenario mismatches. Hence, the AGSC based adaptive MIMO radar beamformer effectively deals with the performance degradation caused by scenario mismatches without resorting to any robust optimization algorithms. Performance analysis and complexity evaluation regarding the AGSC based adaptive MIMO radar beamformer are presented. Simulation results are also provided for confirmation and comparison.

Wind and river effects on a coastal current in Chatham Sound, British Columbia

Chatham Sound is an ecologically and economically important semi-enclosed basin in the northeast Pacific which has received only limited oceanographic attention. Here we investigate the surface circulation in the southern Sound by analyzing hourly current fields obtained from a high-frequency (HF) radar array, installed there in 2017 and still in operation, as well as other hydrographic and mooring measurements that allow us to characterize subsurface features at several specific locations during 2018 and 2019, and satellite imagery processed to obtain a measure of suspended particulate matter at high spatial resolution. We find that the surface circulation is dominated by the plume of the Skeena River, which flows into the southeast corner of the Sound. On average, this plume forms a northward flowing coastal current in the eastern half of the Sound, and is turbid during the freshet. The plume width changes only marginally even though the Skeena’s flow changes seasonally by a factor of about 7. However, the depth of the plume and its salinity is dramatically different during the early summer freshet compared to values in winter. Fastest plume currents appear near the offshore edges of the plume, even though the plume depth is greatest near the coast. We show that these features are consistent with those predicted from an analytical 1-1/2 layer buoyant coastal current model. Winds can accelerate or retard the coastal current; when strong enough the flow is arrested and turbid plume water fills the southern Sound.

Digital modelling method of coal-mine roadway based on millimeter-wave radar array

The roadway space of coal mine is narrow, and the illumination is low and uneven. Dynamic mining is accompanied by dust and water mist. The accuracy and reliability of roadway data collected by vision and laser sensors are poor. Based on this, a digital modeling method of coal mine roadway based on millimeter-wave radar array is proposed. Firstly, aiming at the problem of complex environmental interference, combined with the characteristics of small amount of single frame data of millimeter-wave point cloud, a multi-layer filtering noise reduction processing and dynamic subgraph registration method of millimeter-wave point cloud is proposed to filter out interference points and realize single radar point cloud registration. Secondly, aiming at the problem that a single millimeter-wave radar cannot scan the complete roadway information at one time, combined with the characteristics of small elevation field of view of millimeter-wave radar, a millimeter-wave radar array acquisition system is built, and an improved iterative closest point (ICP) registration algorithm based on point cloud features is established to construct the roadway point cloud fusion model. Finally, aiming at the problem of uneven and sparse point cloud after array fusion, a Poisson surface reconstruction method based on point cloud density weighted interpolation is proposed to refine the roadway structure and realize the accurate reconstruction of digital roadway model. The experimental results show that the digital modeling method of millimeter-wave radar array can accurately obtain the information of roadway surrounding rock, the density of roadway point cloud is increased by 22.4%, and the average absolute error percentage of the width and height of the reconstructed roadway model is only 0.82% and 0.72%, which provides a new research method for the reconstruction of underground roadway and an important basis for the digital modeling method of coal mine roadway.

A Method to Enhance the Calibration Performance of Passive Radar Arrays in DTMB Signal Environment

A Method to Enhance the Calibration Performance of Passive Radar Arrays in DTMB Signal Environment

Research on a Near-Field Millimeter Wave Imaging Algorithm and System Based on Multiple-Input Multiple-Output Sparse Sampling

In order to reduce the hardware cost and data acquisition time in near-field scenarios, such as airport security imaging systems, this paper discusses the layout of a multiple-input multiple-output (MIMO) radar array. In view of the existing multi-input multiple-output imaging algorithm, the reconstructed image artifacts and aliasing problems caused by sparse sampling are discussed. In this paper, a multi-station radar array and a corresponding sparse MIMO imaging algorithm based on combined sparse sub-channels are proposed. By studying the wave–number spectrum of backscattered MIMO synthetic aperture radar (SAR) data, the nonlinear relationship between the wave number spectrum and reconstructed image is established. By selecting a complex gain vector, multiple channels are coherently combined effectively, thus eliminating aliasing and artifacts in the reconstructed image. At the same time, the algorithm can be used for the MIMO–SAR configuration of arbitrarily distributed transmitting and receiving arrays. A new multi-station millimeter wave imaging system is designed by using a frequency-modulated continuous wave (FMCW) chip and sliding rail platform as a planar SAR. The combination of the hardware system provides reconfiguration, convenience and economy for the combination of millimeter wave imaging systems in multiple scenes.

Continuous Respiratory Rate Estimation Approach Based on Phase Features Using Array Radar in Home Sleeping Monitoring

Continuous Respiratory Rate Estimation Approach Based on Phase Features Using Array Radar in Home Sleeping Monitoring

Low SLL Control of Two-Way Pattern in Shared Circular Planar Radar Arrays

Low SLL Control of Two-Way Pattern in Shared Circular Planar Radar Arrays

Mutual coupling effects in 2×2 antenna array for ground penetrating radar on multilayered soil

<span>Caral stands as the Americas’ oldest city, boasting a heritage spanning 5,000 years. Over time, various natural forces have woven a complex geological stratum. To gain a deeper understanding of the Caral civilization, non-intrusive exploration methodologies like ground penetrating radar (GPR) are beginning to be used. This method safeguards the integrity of ancient subterranean remains. A GPR system is in development, tailored to the <br /> [200-500] MHz range, employing a 2×2 antenna array with dual polarization. These features enhance resolution without compromising penetration depth. However, using multiple antennas within complex, multi-layered environments introduce impedance band constraints and exacerbates antenna coupling issues. This study assesses the coupling of two antenna candidates: the Vivaldi with defected ground structures (DGS) and the log periodic dipole array (LPDA). The scattering parameters show that the LPDA antenna performed better considering measured and simulated data. Cross-polarization exhibited a broader bandwidth in the LPDA antenna, evident in both simulated and measured data. Additionally, a comprehensive comparison of GPR simulations for each antenna type within an 11-level multilayer medium, with different electromagnetic properties, further highlights LPDA. This antenna boasts a 209 MHz bandwidth and a coupling better than -23 dB for the cross-polarization configuration, firmly showing its best performance.</span>

Robust SR-STAP algorithms in partly calibrated arrays for airborne radar

Sparse recovery based space-time processing (SR-STAP) techniques are capable of achieving satisfactory clutter suppression and target detection performance, even with limited training samples. The majority of existing approaches are developed under the assumption of ideal uniform linear arrays, where no imperfections are present. In this study, we consider the robust STAP problem in the context of airborne partly calibrated array (PCA) composed of several well calibrated subarrays with unknown inter-subarray gain-phase and displacement errors. Initially, the space-time signal for airborne STAP radar based on PCAs is modeled. Subsequently, the authors propose two robust SR-STAP algorithms, considering both grid-based and gridless methods, leveraging the block-sparsity and low rank structural characteristics inherent in the signal model. Extensive numerical experiments have shown the significant performance benefits including small sample applicability and resilience to inter-subarray gain-phase and displacement errors.

FRACTAL GEOMETRY-BASED RESOURCE ALLOCATION FOR MIMO RADAR

The netted Collocated Multiple-Input Multiple-Output (C-MIMO) radar systems have attracted widespread attention due to their high resolution and excellent target detection capabilities. The self-similarity and spatial filling properties of fractal geometry enable antenna layouts to function effectively across multiple scales and frequency bands, which helps improve the overall performance and resource utilization of systems. In this paper, a radar array element model based on the Fudgeflake fractal is used to establish a target localization performance model directly related to power bandwidth allocation. Based on the model, a three-step solving strategy was designed with the Sequence Quadratic Program (SQP) algorithm as the foundation to achieve optimized allocation of power and bandwidth while maximizing overall performance. Experimental results demonstrate that under this algorithm, the use of power bandwidth resources is optimized through fractal geometry-based design.

Beamforming for Unmanned Aerial Vehicle Swarm-based Distributed Radar Array: Theoretical Analysis and Engineering Demonstration

Beamforming for Unmanned Aerial Vehicle Swarm-based Distributed Radar Array: Theoretical Analysis and Engineering Demonstration

Antenna Pattern Calibration Method for Phased Array of High-Frequency Surface Wave Radar Based on First-Order Sea Clutter

The problem of accurate source localization has been an area of focus in high-frequency surface wave radar (HFSWR) applications. However, antenna pattern distortion (APD) decreases the direction-of-arrival (DOA) estimation performance of the multiple signal classification (MUSIC) algorithm. Up to now, limited studies have been conducted on the calibration of antenna pattern distortion for phased arrays in HFSWR. In this paper, we first analyze the effect of APD on the performance of the MUSIC algorithm through estimation of accuracy and angular resolution. We demonstrate that using the actual pattern (or say APD) can improve DOA estimation performance. Based on this proposition, we propose a novel iterative calibration method that employs the first-order sea clutter data and can jointly estimate DOA and APD in an iterative way. To obtain available calibration points, we introduce the extraction methods of the first-order sea clutter spectrum and single-DOA spectrum points. Meanwhile, in each iteration, the Beamspace MUSIC algorithm and artificial hummingbird algorithm (AHA) are utilized to estimate the DOA and APD, respectively. Numerical results reveal a good coincidence between the actual pattern and the estimated APD. We also apply this method to process the experimental data of HFSWR. We obtain the APD vector of the real phased array and improve the direction-finding performance of several real ship targets using this vector. Both numerical and experimental results prove the correctness of our proposed calibration method.

A 223–276-GHz Cascadable FMCW Transceiver in 130-nm SiGe BiCMOS for Scalable MIMO Radar Arrays

This article reports a 223–276-GHz monostatic frequency-modulated continuous-wave (FMCW) radar transceiver (TRX) chip. The TRX is suitable for building massive multiple-input multiple-output (MIMO) radar arrays in the daisy-chain topology because of its cascadable feature based on the injection-locking feedthrough technique. The TRX is based on 18 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> frequency multiplication chain that can be fed by either an external signal generator (SG) or its internal voltage-controlled oscillator (VCO). The modulation bandwidth (BW) is about 53 GHz when the internal VCO is activated, resulting in a range resolution of better than 3 mm. The peak output power is 3.1 dBm at 240 GHz with a 3-dB BW of 41 GHz. Its receiver (RX) channel is based on the in-phase/quadrature architecture enabling complex signal sampling. The minimum single-sideband (SSB) noise figure (NF) is 18.7 dB at 255 GHz, and the average value is 20.7 dB. The TRX chip includes an on-chip antenna coupled with a silicon lens, offering a peak effective isotropic radiated power (EIRP) of 27 dBm at 240 GHz. The TRX consumes a dc current of 234 and 270.1 mA from a single supply voltage of 3.3 V for external and internal VCO operations, respectively. The chip occupies a total area of 2.7 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (2.16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 1.26 mm).

A Novel two-dimensional DOA Estimation Algorithm for Low Elevation Targets

This paper proposes a fast Two-Dimensional DOA Estimation algorithm for low-elevation targets of Very High Frequency (VHF) Array Radar using an estimation method based on the Alternating Direction Method of Multipliers (ADMM). The method firstly utilizes the uncoupling characteristics of azimuth and pitch angle under a uniform planar array, to convert the two-dimensional angle estimation problem into two one-dimensional DOA estimation problems. The target information is extracted by digital beamforming in the azimuth and elevation dimensions. Finally, the Alternating Direction Method of Multipliers is used for estimation of the azimuth and pitch angle. This method avoids the two-dimensional joint estimation, which is complex in the calculation, the complexity is greatly reduced, and the operation process does not require Eigenvalue decomposition, further improving the operation efficiency.

RadarSense: Accurate Recognition of Mid-air Hand Gestures with Radar Sensing and Few Training Examples

Microwave radars bring many benefits to mid-air gesture sensing due to their large field of view and independence from environmental conditions, such as ambient light and occlusion. However, radar signals are highly dimensional and usually require complex deep learning approaches. To understand this landscape, we report results from a systematic literature review of ( N =118) scientific papers on radar sensing, unveiling a large variety of radar technology of different operating frequencies and bandwidths and antenna configurations but also various gesture recognition techniques. Although highly accurate, these techniques require a large amount of training data that depend on the type of radar. Therefore, the training results cannot be easily transferred to other radars. To address this aspect, we introduce a new gesture recognition pipeline that implements advanced full-wave electromagnetic modeling and inversion to retrieve physical characteristics of gestures that are radar independent, i.e., independent of the source, antennas, and radar-hand interactions. Inversion of radar signals further reduces the size of the dataset by several orders of magnitude, while preserving the essential information. This approach is compatible with conventional gesture recognizers, such as those based on template matching, which only need a few training examples to deliver high recognition accuracy rates. To evaluate our gesture recognition pipeline, we conducted user-dependent and user-independent evaluations on a dataset of 16 gesture types collected with the Walabot, a low-cost off-the-shelf array radar. We contrast these results with those obtained for the same gesture types collected with an ultra-wideband radar made of a vector network analyzer with a single horn antenna and with a computer vision sensor, respectively. Based on our findings, we suggest some design implications to support future development in radar-based gesture recognition.

Structural Enhancement and Thermal Deformation Analysis of Antenna Arrays in Vehicle-Mounted Phased Array Radar: A Heat Dissipation Perspective

Structural Enhancement and Thermal Deformation Analysis of Antenna Arrays in Vehicle-Mounted Phased Array Radar: A Heat Dissipation Perspective

Generalised two‐level nested multiple‐input multiple‐output radar direction of arrival estimation with high degrees of freedom and low mutual coupling

AbstractTo address the problems of traditional two‐level nested arrays (TTNA) with low degrees of freedom and high mutual coupling, a generalised two‐level nested MIMO radar array with high degrees of freedom and low mutual coupling for the direction of arrival (DOA) estimation is proposed. First, two coprime expansion factors are introduced in the TTNA to mitigate mutual coupling among array elements and enhance its degrees of freedom. Secondly, the range of consecutive lags and the total number of virtual array elements are derived in closed form under the structures of ‘sum–difference co‐array’. Finally, utilising the atomic norm minimisation theory, the authors address the issue of discrete holes caused by different coprime expansion factors through filling in virtual arrays at discontinuities. Furthermore, a convex optimisation model to recover equivalent received signals from these filled virtual arrays is established, which is combined with a multiple signal classification algorithm for DOA estimation. Simulation results validate the rationality of the array structure and demonstrate the effectiveness of the algorithm.

Reducing the Sidelobes in Doppler-Range Beam Pattern and Controlling the Frequency Channel in SIAR

Synthetic impulse and aperture radar (SIAR) is a multi-input multi-output orthogonal multicarrier frequency radar, kind of frequency diverse array (FDA). This radar has omnidirectional emission in the transmitter and each receiver or receiving array can form a beam. The 4D matched filter of this radar’s circular arrays can reveal the range, elevation angle, azimuth angle, and Doppler. The existence of a high sidelobe in the range-Doppler is one of the significant challenges of this radar, and pulse-to-pulse frequency code non-agile (PPFCNA) and pulse-to-pulse frequency code agile (PPFCA) are often used to reduce it. Weighting is one of the available methods for reducing sidelobes in array radars, but weighting in the matched filter is more effective in SIAR radars due to their ability to transmit signals with different and orthogonal frequencies. This paper proposes the use of amplitude weighting in the submatched filter, which is made possible by increasing the degree of freedom in the SIAR process. In this method, each receiver’s signal is independently processed and weighted with a submatched filter. Then, a synthetic pulse is formed by combining the data from multiple channels. The output of the simulation with weighting in the matched filter for the PPFCNA indicates an 8.7908 dB reduction in sidelobes, while the output for the PPFCA indicates a 3.3779 dB reduction in sidelobes.