Phased Array Radar Research Articles

Rapid Sampling and Polarimetric Statistics of Lightning With a Phased Array Radar

AbstractPrevious studies of lightning detection by radar mostly consisted of observations with reflector‐antenna systems yielding slow volume scan times. Phased array radars offer much faster scan times that are likely to capture echoes from propagating lightning channels. Rapidly updated range‐height indicator scans were used to observe severe storms that occurred in central Oklahoma with the fully digital S‐band Horus PAR to examine echoes from lightning plasma. Numerous lightning echoes were observed during the sampling period in good spatial and temporal agreement with lightning mapping array detections of very high frequency radiation sources. Statistically, they result in increased horizontal reflectivity factor, deviations in radial velocity and spectrum width, highly variable differential reflectivity and differential phase, and decreases in correlation coefficient. Results presented also highlight the capability of phased array radars to better observe lightning compared to current radars, and aid in the study of storm electrification and lightning physics.

Doppler Circulation and Areal Contraction Rate as Detected and Measured by a Phased-Array Radar: The El Reno, Oklahoma Tornado of 31 May 2013

Abstract A single-Doppler technique is developed to utilize data acquired by a phased-array radar that derives observed circulations and areal contraction rates through analyses of circuits at constant radii around the circulation center of a powerful tornadic supercell near El Reno, Oklahoma, on 31 May 2013. Since the rapid-scan, phased-array radar measures only the component of 3-D flow in the radar viewing direction, velocity normal to the beam is set to zero to enable the calculation of circulations and areal contraction rates of circles within a surface of constant elevation angle. To obtain reliable standard measures of vortex strength, mean Doppler velocities are bilinearly interpolated to points on circles of specified radii concentric with circulation centers. The Doppler circulations around and material contractions of these circles are then calculated. Circulation is large and flow is convergent just prior to tornado formation. At its maximum size and intensity, the circulation of the tornado was very large, 9 × 105 m2 s−1 at a height of 1.5 km. As the tornado’s size increased, the divergence within it increased. During the tornado’s mature stage, areal rates of vortex core change from expansion to contraction to expansion over a period of 12 minutes. The use of rapid volumetric updates of approximately 1 min (or faster) available with PAR technology to track significant Doppler circulations and areal contraction rates may provide indications of imminent tornadogenesis and important updates of tornadoes in progress, though much future work remains to quantify any potential warning implications.

Integrated Optical Tunable Delay Line and Microwave Photonic Beamforming Chip: A Review

AbstractThe microwave photonic (MWP) beamforming chip is a crucial component for achieving the miniaturization of optically controlled phased array radar systems. It addresses the unwanted ‘beam squint’ effect of traditional electronic antenna arrays in processing wideband RF signals through optical tunable delay lines (OTDLs), which has garnered significant attention and research efforts in recent years. This review provides a comprehensive overview of the latest research progress on the classification, working principle, calibration and delay measurement methods, driving and control technologies, and system function verifications of OTDL and MWP beamforming chips. Also, discussions about the challenges that need to be addressed and the future development trends for this technology are given.

Non-Myopic Beam Scheduling for Multiple Smart-Target Tracking in Phased Array Radar Networks.

This paper addresses beam scheduling for tracking multiple smart targets in phased array radar networks, aiming to mitigate the performance degradation in previous myopic scheduling methods and enhance the tracking performance, which is measured by a discounted cost objective related to the tracking error covariance (TEC) of the targets. The scheduling problem is formulated as a restless multi-armed bandit problem, where each bandit process is associated with a target and its TEC states evolve with different transition rules for different actions, i.e., either the target is tracked or not. However, non-linear measurement functions necessitate the inclusion of dynamic state information for updating future multi-step TEC states. To compute the marginal productivity (MP) index, the unscented sampling method is employed to predict dynamic and TEC states. Consequently, an unscented sampling-based MP (US-MP) index policy is proposed for selecting targets to track at each time step, which can be applicable to large networks with a realistic number of targets. Numerical evidence presents that the bandit model with the scalar Kalman filter satisfies sufficient conditions for indexability based upon partial conservation laws and extensive simulations validate the effectiveness of the proposed US-MP policy in practical scenarios with TEC states.

Online Calibration for Networked Radar Tracking of UAS

The need for effective tracking mechanisms of small unmanned aircraft systems (sUAS) has become crucial as their use has increased in populated areas. This paper presents a practical tracking solution for sUAS using a network of phased array radars. Achieving optimal system performance while tracking the sUAS requires extrinsic calibration of the individual radar systems to a common frame of reference. We propose a straightforward calibration solution based upon the orthogonal Procrustes formulation that uses radar measurements from ground-mounted radar associated with real-time-kinematic global positioning system (RTK-GPS) data. Two variations of the calibration are provided: a batch processing method, and an online method for real-time adjustments. This paper provides a practical analysis of the advantages and disadvantages associated with both calibration methods. This assessment of the calibration methods, along with an evaluation of the radar network’s sUAS tracking ability, is validated by simulation studies and hardware tests. The hardware experiments especially provide valuable insights into the practical implications of the proposed tracking solution.

A review of research on optical true time delay technology

Light controlled phased array has the advantages of fast response speed, compact system, diverse functions, and flexible control, and has been widely applied in many scientific and technological fields. Optical true delay technology (OTTD) is the most direct technical means to achieve phase delay of optical carrier signals, and it is also the most basic technical means to implement optical controlled beamforming systems. In order to fully understand the optical true delay technology, this article first elaborates on the principle of phased array antennas and the reasons for beam strabismus, and analyzes the impact of true delay on the performance of phased array radar. Then, the basic principle, technological progress, and related applications of optical true delay are introduced. Taking four common structures of optical true delay lines as examples,which are micro-ring resonant cavity array, grating ture time delay line, multi-path switchable optical ture time delay line（OTTDL）, and wavelength selective optical delay line, their performance in delay accuracy, adjustable delay range, and frequency bandwidth are compared. Finally, the current problems and future development trends of optical controlled beamforming technology were summarized.

Evaluation of a double-lens dielectric radome using a microstrip patch antenna for electromagnetic applications

The advancement of increasingly powerful antennas has increased the complexity of radome electromagnetic (EM) design and analysis. The antenna systems are protected from environmental influences by radomes, which are dielectric and electromagnetically transparent structures. Because the presence of the radome affects the performance parameters of the antenna, such as the radiation pattern, reflected power, and side lobe level, its design should not be done independently of the antenna analysis. The great majority of ground-based hemispherical radomes are used for satellite communication antennas, commercial and military radars, telemetry systems, and other uses. Patch antennas, reflector antennas, phased array radars, and other antenna systems are used in these applications. The operational effectiveness of a radome architecture for housing multiple patch antenna systems is proposed and evaluated. The proposed line of work includes antenna-radome interaction analyses, electromagnetic designs for radome walls, and radiation patterns for reflector antennas. COMSOL Multiphysics was used to develop the EM radome and examine the antenna-radome interaction. The findings of a comprehensive analysis into the differences in radiation patterns produced by patch antennas with and without radomes are presented in this article. At a frequency of 1.62 GHz, a plot and investigation of the far-field gain of the microstrip patch antenna with and without radome were done. The radome is estimated to add 0.09 dBi to the gain boost experienced by the microstrip patch antenna.Abbreviations: EM, Electromagnetic; DSF, Dielectric space frame radome; IFR, Induced field ratio; RF, Radio frequency; VSWR, Voltage standing wave ratio; FEM, Finite element method; SRR, Split ring resonator; CATR, Compact antenna test range; DUT, Device being tested; LHM, Left-handed metamaterials; PML, Perfectly matched layer; PTFE, Polytetrafluoroethylene.

Topology-optimized terahertz real-time reconfigurable multifunctional liquid-crystal-coding metasurface

In this paper, a reflective terahertz reconfigurable multifunctional coding metasurface based on topology optimization using liquid crystal (LC) is presented. First, the LC metasurface unit is topologically optimized using the NSGA-II multi-objective optimization algorithm. By applying the bias voltage to dynamically adjust the dielectric constant of the LC, the metasurface unit is capable of 2-bit coding at the frequency of 0.67 THz. Then, based on the designed metasurface unit, the array arrangements of the coding metasurface are reversely designed, which makes the metasurface realize flexible control and dynamic switching between beam assignment and vortex beam generation. The results show that for the beam assignment, the single-beam and multi-beam control can be realized with the reflected electromagnetic waves at continuous arbitrary angles in the range of elevation angle of 40° and azimuth angle of 360°. Moreover, the elevation angle and azimuth angle of each beam in the multi-beam can be controlled independently. Using the Fourier convolution addition operation, the control range of the single-beam elevation angle can be expanded. For the vortex beam, the single vortex beam and the multi-vortex beam can be generated in the range of elevation angle of 40° and azimuth angle of 360° with topological charges l=±1, ±2, ±3 at arbitrary angles. This provides flexibility and diversity in the generation of vortex beams. Therefore, the proposed terahertz LC metasurface can realize flexible control of reconfigurable functions and has certain application prospects in terahertz communication, phased array radar, and vortex radar.

Operational Phased Array Radar Network for Natural Hazard Monitoring and Warnings in Urban Environments over the Greater Bay Area, China

Abstract The continuous development of modern Doppler weather radars has substantially augmented our capacity to monitor severe convective storms and gain insights into their dynamic and microphysical structures. Although conventional parabolic antenna-based S-band operational radars are valuable, they exhibit limitations such as low scanning speed and reduced information acquisition in the low atmosphere region, particularly at far ranges from the radar, leading to suboptimal observations of fast-evolving storms. To address these limitations, a dense X-band polarimetric phased array radar (PAR) network, consisting of more than 50 radars, has been strategically constructed and deployed in the Greater Bay Area in South China, which is currently the largest PAR network worldwide. The PARs exhibit satisfactory performance in hydrometeor classification, hail identification, and quantitative precipitation estimation, demonstrating reliable polarimetric data quality. The paper also presents compelling evidence demonstrating the effectiveness of the PAR network in detecting the tornado vortex and capturing fine horizontal and vertical structures of convective storms when compared to nearby S-band operational radars. In addition, the assimilation of supplemental PAR data using the ensemble Kalman filter has yielded discernible vortex circulation fields for tornadic storms, enabling effective prediction of tornadogenesis, which is unattainable solely by assimilating S-band operational radar data. As the PAR network is put into operational use, significant advancements are anticipated in understanding and monitoring severe weather systems in South China.

M2CS: A microwave measurement and control system for large-scale superconducting quantum processors

Abstract As superconducting quantum computing continues to advance at an unprecedented pace, there is a compelling demand for the innovation of specialized electronic instruments that act as crucial conduits between quantum processors and host computers. Here, we introduce a microwave measurement and control system (M2CS) dedicated to large-scale superconducting quantum processors. M2CS features a compact modular design that balances overall performance, scalability and flexibility. Electronic tests of M2CS show key metrics comparable to commercial instruments. Benchmark tests on transmon superconducting qubits further show qubit coherence and gate fidelities comparable to state-of-the-art results, confirming M2CS’s capability to meet the stringent requirements of quantum experiments running on intermediate-scale quantum processors. The compact and scalable nature of our design holds the potential to support over 1000 qubits after upgrade in stability and integration. The M2CS architecture may also be adopted to a wider range of scenarios, including other quantum computing platforms such as trapped ions and silicon quantum dots, as well as more traditional applications like microwave kinetic inductance detectors and phased array radar systems.

Design and On-Orbit Performance of Ku-Band Phased-Array Synthetic-Aperture Radar Payload System

The current emphasis in the advancement of space-based synthetic-aperture radar (SAR) is on lightweight payloads under 100 kg with resolutions surpassing 1 m. This focus is directed toward meeting the launch criteria for multiple satellites on a single rocket and cutting costs. This article discusses the creation and progress of a Ku-band SAR payload for the Taijing-4(03) satellite, launched on 23 January 2024 and accompanied by four other satellites. The SAR payload design was customized to meet the demands of a micro-nano satellite platform, resulting in a lightweight, flat design weighing less than 80 kg, seamlessly integrated with the plate-shaped satellite platform. The article also introduces a beam optimization strategy for the phased array SAR antenna, significantly boosting the SAR system’s performance. The SAR payload provides various operating modes like slide-spot, strip, Scan 1, Scan 2, and others, with a maximum achievable resolution exceeding 1 m. Extensive in-orbit testing of the payload produced numerous high-quality SAR images with potential uses in emergency disaster mitigation, safeguarding ecosystems, monitoring forests, managing crops, tracking sea ice, and more.

A Survey of Phase Shifters for Microwave Phased Array Systems

ABSTRACTPhased Array Systems (PASs) are extensively used in radar and telecommunication systems for diverse applications, including military surveillance and wireless broadband communication. Besides, they are becoming increasingly indispensable in modern applications such as multi‐function phased array radars for weather monitoring and aircraft tracking or high‐throughput satellite systems, which aim to provide fast broadband connectivity in remote areas. Despite the numerous advantages of phased array systems with RF phase shift, including high signal‐to‐noise and signal‐to‐interference ratios, as well as low complexity, they present a few limitations, including high cost and large chip areas. The cost and size of PASs are mainly dependent on the RF phase shifters, which are essential to their operation. This article describes the different types of phase shifters (mechanical, ferromagnetic/magnetic, electromechanical, and electronic). It compares their performance metrics, highlighting that electronic phase shifters are the most common type used in modern PASs. In this regard, a comparative study of different subcategories of electronic phase shifters, such as the switched‐type, reflective‐type, loaded‐transmission line, and vector‐sum phase shifters, are explored along with their advantages, drawbacks and state‐of‐art techniques used to address their limitations. Therefore, this article may serve as a reference for research milestones on RF phase shifters.

Observation of Electrical Alignment Signatures in an Isolated Thunderstorm by Dual‐Polarized Phased Array Weather Radar and the Relationship With Intracloud Lightning Flash Rate

AbstractThe electrical alignment signatures of ice crystals in the middle and upper parts of a thunderstorm have a physical connection with the strong electric fields within the cloud. By taking advantage of the high spatio‐temporal resolution of an X‐band dual‐polarized multiparameter phased array radar, this paper employs negative KDP signatures to investigate the variation of electric fields in an isolated thunderstorm within its evolution, and the relationship between the negative KDP signatures and intracloud (IC) lightning activity. The results show that the radar‐inferred strong electric fields distributed in a region of about 8.5–10 km during the developing stage, then extended from about 10 km to the cloud top during the mature stage, with an increasing IC lightning flash rate before the end of the mature stage. Subsequently, the electric fields weakened associated with a large amount of IC lightning discharges. The qualitative analysis results indicate that the evolution of the radar‐inferred electric fields associated with the upper charge regions is consistent with the electrification process in the isolated thunderstorm, inferred by the IC lighting activity. In addition, there is a tendency for the increased IC lightning rate as the decrease in average composite KDP in the middle and upper layers of the thunderstorm, with a time lag of about 5.5 min between the minimum average composite KDP and the peak IC lightning rate, while a good correlation between the negative KDP volume and the IC lightning flash rate at a lag of approximately 9 min.

Real-Time Dwell Scheduling Based on a Unified Pulse Interleaving Framework for Phased Array Radar

Real-Time Dwell Scheduling Based on a Unified Pulse Interleaving Framework for Phased Array Radar

CUSTR- A VHF phased array radar for observation of atmospheric dynamics and ionospheric plasma irregularities

A VHF phased array radar for atmospheric dynamics observation is installed at the University of Calcutta, Kolkata. The Calcutta University Stratosphere-Troposphere Radar (CUSTR) operates at 53 MHz with 475 three sub-element Yagi-Uda antenna array. The CUSTR system is a high-power fully active phased array system with a dedicated 2 kW solid-state Transmit-Receiver Module (TRM) attached to each antenna, providing a total peak power of 950 kW with 47.5 kW average power at 5% maximum duty ratio. The system provides electronic beam steering capability to steer the beam 360° in azimuth direction with a maximum off-zenith angle of 40°. The array is configured with 25 sub-arrays and operates either in a combined mode in Doppler Beam Swinging or in Spaced Antenna mode using a multi-channel digital receiver system. The TRM has been designed to provide a very short pulse of 0.5 µs and a long pulse of 128 µs. The system description along with the initial scientific observations such as atmospheric boundary layer, troposphere-lower stratosphere wind measurements along with preliminary wind validation, mesosphere echoes and ionosphere irregularities are presented.

Application of Instance Segmentation to Identifying Insect Concentrations in Data from an Entomological Radar

Entomological radar is one of the most effective tools for monitoring insect migration, capable of detecting migratory insects concentrated in layers and facilitating the analysis of insect migration behavior. However, traditional entomological radar, with its low resolution, can only provide a rough observation of layer concentrations. The advent of High-Resolution Phased Array Radar (HPAR) has transformed this situation. With its high range resolution and high data update rate, HPAR can generate detailed concentration spatiotemporal distribution heatmaps. This technology facilitates the detection of changes in insect concentrations across different time periods and altitudes, thereby enabling the observation of large-scale take-off, landing, and layering phenomena. However, the lack of effective techniques for extracting insect concentration data of different phenomena from these heatmaps significantly limits detailed analyses of insect migration patterns. This paper is the first to apply instance segmentation technology to the extraction of insect data, proposing a method for segmenting and extracting insect concentration data from spatiotemporal distribution heatmaps at different phenomena. To address the characteristics of concentrations in spatiotemporal distributions, we developed the Heatmap Feature Fusion Network (HFF-Net). In HFF-Net, we incorporate the Global Context (GC) module to enhance feature extraction of concentration distributions, utilize the Atrous Spatial Pyramid Pooling with Depthwise Separable Convolution (SASPP) module to extend the receptive field for understanding various spatiotemporal distributions of concentrations, and refine segmentation masks with the Deformable Convolution Mask Fusion (DCMF) module to enhance segmentation detail. Experimental results show that our proposed network can effectively segment concentrations of different phenomena from heatmaps, providing technical support for detailed and systematic studies of insect migration behavior.

Intelligent decision-making algorithm for airborne phased array radar search tasks based on a hierarchical strategy framework

To address the guided search task of airborne phased array radar in the scenarios of large airspace with widespread distribution of cluster targets in Beyond Visual Range (BVR) air combat, a hierarchical strategy framework based on deep reinforcement learning is proposed to guide different stages of search tasks. Firstly, an airspace set-covering model and a radar parameter optimization model for the guided search task of cluster targets are established. Secondly, the hierarchical strategy framework including upper-level and lower-level strategies is constructed based on the above models. Finally, the happo-rgs algorithm is proposed for feature extraction from Markov continuous observation sequences, to enhance the training effectiveness and improve the algorithm convergence speed. Simulation results show that the trained agent can make precise autonomous decisions rapidly based on airspace-target covering situation and target guidance information which significantly improves the radar search performance in the forementioned scenarios compared to traditional algorithms.

An Algorithm to Retrieve Range Ocean Current Speed under Tropical Cyclone Conditions from Sentinel-1 Synthetic Aperture Radar Measurements Based on XGBoost

In this study, a novel algorithm to retrieve the current speed along the range direction under extreme sea states is developed from C-band synthetic aperture radar imagery. To this aim, a Sentinel-1 (S-1) dual-polarized synthetic aperture radar (SAR) dataset consisting of 2300 images is collected during 200 tropical cyclones (TCs). The dataset is complemented with collocated wave simulations from the Wavewatch-III (WW3) model and reanalysis currents from the HYbrid Coordinate Ocean Model (HYCOM). The corresponding TC winds are officially released by IFRMER, while the Stokes drift following the wave propagation direction is estimated from the waves simulated by WW3. In this study, first the dependence of wind, Stokes drift, and range current on the Doppler centroid anomaly is investigated, and then the extreme gradient boosting (XGBoost) machine learning model is trained on 87% of the S-1 dataset for range current retrieval purposes. The rest of the dataset is used for testing the retrieval algorithm, showing a root mean square error (RMSE) and a correlation coefficient (r) of 0.11 m/s and 0.97, respectively, with the HYCOM outputs. A validation against measurements collected from two high-frequency (HF) phased-array radars is also performed, resulting in an RMSE and r of 0.12 m/s and 0.75, respectively. Those validation results are better than the 0.22 m/s RMSE and 0.28 r achieved by the empirical CDOP model. Hence, the experimental results confirm the soundness of the XGBoost, exhibiting a certain improvement over the empirical model.

Joint Node Selection and Power Allocation in Phased Array Radar Network With LPI Property and Spectral Compatibility for Multitarget Tracking

Joint Node Selection and Power Allocation in Phased Array Radar Network With LPI Property and Spectral Compatibility for Multitarget Tracking

A Single Layer Low Axial Ratio Circularly Polarized Planar Wide-Angle Scanning Phased Array

This paper proposes a circularly polarized planar wide-angle scanning phased array radar. The structure of the proposed array element is a windmill-type patch with an octagon-shaped series power divider. The proposed array exhibits a low axial ratio because the element has a wide 3-dB axial ratio beamwidth and the array topology uses the sequential rotation technique. Test results show that the proposed 8 × 8 uniform planar array can realize two-dimensional circularly polarized scanning from −60° to +60° in the working band of 3.43–3.48 GHz. The coverage gains of θ = ±60° are about 3 dB lower than the gain when the main beam points at θ = 0°. Moreover, in the scanning mentioned above airspace, the scanning beam axial ratio is below 0.5 dB in the xz-plane (φ = 0°) and yz-plane (φ = 90°) and below 1.4 dB in the D-plane (φ = 45°). Another notable feature is the single-layer structure, and its profile is only 0.08λ0 at the center wavelength. This good low- axial ratio and low-profile characteristics make the proposed array potentially applicable to low-orbit satellite communications.