Target Radar Cross Section Research Articles

Physical Optics Radar Cross Section predictions for an anti-ship cruise missile

The capability of the first strike is crucial in the modern battlefield. An important parameter is the radar signature or Radar Cross Section (RCS) of a weapon system, such as a fighter aircraft, a warship, or a missile, affecting the range at which this weapon system would be detected as a target by an enemy radar. If the attacker is detected too late, there will be minimal time for the defender to react, possibly not sufficient to counter the threat. The RCS of a weapon system is considered generally as classified information. However, it can be measured at a suitable measurement test range, if that weapon system is available. Otherwise, it can be predicted with the help of computational electromagnetics. Concerning the second approach, the following procedure was recently proposed: construction of a three-dimensional model of a target, based on available images and any relevant data, and then computation of the target RCS, with the Physical Optics approximative method. In the present approach, this procedure is applied to an anti-ship cruise missile in order to compute its RCS. Finally, the expected detection range for various naval radars is calculated.

Practical Investigation of a MIMO radar system capabilities for small drones detection

The latest progress of the multiple-input multiple-output (MIMO) radar system developed for small drones detection at Beijing Institute of Technology is presented herein. A low-cost S-band MIMO scanning radar system is designed for the detection of small drones. A practical design optimisation and implementation of a sparse array covering the whole airspace, and a target-based MIMO radar array calibration method to improve the signal-to-noise ratio of the target are proposed. An experiment in the microwave chamber was conducted to verify the designed sparse-array beam-pattern, and measurement campaigns for small drones were performed to test the system performance where the radar achieved detection and tracking of a small DJI-Phantom 4 drone at a range of up to 5 km. Target features, including micro-Doppler and radar cross-section signatures were extracted to assist target classification. The experimental results indicate that the system has promising capability in small drones detection and tracking, despite the challenges of low dwell time on targets due to the scanning nature of the system.

Dynamic RCS Modelling of Launch Vehicle Prior to Launch for Estimation of Real-time SNR

The Radar Tracking System plays a crucial role in tracking launch vehicles by providing continuous trajectory information in order to assess their performance in real-time for range safety purpose. The target Radar Cross Section (RCS) determines radar tracking efficiency and highly depends on both the target characteristics and the radar parameters. A good amount of RCS is warranted for space-based applications for easy detection and continuous tracking by the radar. It is essential to model and simulate the RCS fluctuations of the launch vehicle prior to launch for estimating the real-time received Signal to Noise Ratio (SNR) variations for its dynamic trajectory. This modelling will aid in selecting the best radar configuration to obtain a good amount of SNR in real-time and it also provides guidance for the radar operation in tracking the target. This paper analysed the RCS fluctuations of the launch vehicle for its dynamic trajectory prior to launch by software simulation and also compute the expected real time launch vehicle SNR variations.

Low-Cost, Wideband Checkerboard Metasurfaces for Monostatic RCS Reduction

This letter presents three wideband checkerboard metasurfaces (CMSs) for monostatic radar cross-section (RCS) reduction realized using low-cost FR4 material. The CMSs designed for the target RCS reduction of 10 dB using the conventional phase deviation condition of 180 ± 37°, when simulated, exhibit an overshoot in the lower frequency band and much higher reductions in the higher band. In order to maximize the bandwidth considering these variations, a constriction of 180 ± 18° in the lower frequency band and a relaxation of 180 ± 48° in the higher frequency band are made to the phase deviation condition. The three CMSs realized using these modifications offer a 10 dB RCS reduction bandwidth over the range of 94%-98%. The simulated and measured results compare favorably.

Parameter Estimation and Target Detection of Phased-MIMO Radar Using Capon Estimator

Phased-Multiple Input Multiple Output (PMIMO) radar is multi-antenna radar that combines the main advantages of the phased array (PA) and the MIMO radars. The advantage of the PA radar is that it has a high directional coherent gain making it suitable for detecting distant and small radar cross-section (RCS) targets. Meanwhile, the main advantage of the MIMO radar is its high waveform diversity gain which makes it suitable for detecting multiple targets. The combination of these advantages is manifested by the use of overlapping subarrays in the transmit (Tx) array to improve the performance of parameters such as angle resolution and detection accuracy at amplitude and phase proportional to the maximum number of detectable targets. This paper derives a parameter estimation formula with Capon's adaptive estimator and evaluates it for the performance of these parameters. Likewise, derivation for expressions of detection performance such as the probability of false alarm and the probability of detection is also given. The effectiveness and validation of its performance are compared to conventional estimator for other types of radars in terms of the effect of the number of target angles, the RCS of targets, and variations in the number of subarrays at Tx of this radar. Meanwhile, the detection performance is evaluated based on the effect of Signal to Noise Ratio (SNR) and the number of subarrays at Tx. The evaluation results of the estimator show that it is superior to the conventional estimator for estimating the parameters of this radar as well as the detection performance. Having no sidelobe makes this estimator strong against the influence of interference and jamming so that it is suitable and attractive for the design of radar systems. Root mean square error (RMSE) on magnitude detection from LS and Capon estimators were 0.033 and 0.062, respectively. Meanwhile, the detection performance for this radar has the probability of false alarm above 10-4 and the probability of detection of more than 99%.

EM Modelling of Monostatic RCS for Different Complex Targets in the Near-Field Range: Experimental Evaluation for Traffic Applications

An evaluation of monostatic radar cross section (RCS) response in the near-field range was performed for several targets with different and complex topologies. The main objective was to provide and validate an efficient tool based on electromagnetic (EM) simulations to characterize a traffic scenario. Thus, a novel method based on the combination of geometrical theory of diffraction (GTD) and physical optics (PO) was used to estimate RCS, and the results were compared with the method of moments (MoM) methodology. The simulations were experimentally validated using a commercial vehicular frequency-modulated continuous wave (FMCW) radar at 24 GHz. With this simple measurement system, RCS measurements can be made using an easier and cheaper process to obtain RCS response in the near-field range, which is the most usual situation for traffic applications. A reasonable agreement between the measurements and the EM simulations was observed, validating the proposed methodology in order to efficiently characterize the RCS of targets typically found in real traffic scenarios.

A Distributed MIMO Radar With Joint Optimal Transmit and Receive Signal Combining

Multiple-input multiple-output (MIMO) radar systems are popular for their ability to mitigate the target radar cross section fluctuations and null Doppler. However, MIMO radar fundamentally suffers from a notable signal-to-noise ratio (SNR) loss compared to an ideal phased-array (PA) radar. In order to overcome this drawback, a distributed MIMO radar scheme with joint optimal transmit and receive signal combining method is proposed in this work. In view of the optimality, the proposed scheme outperforms the most popular combining methods of MIMO radar addressed in the literature. Also, the proposed scheme performs same as the ideal PA radar in case of the nonfluctuating target. In case of fluctuating targets, the proposed scheme outperforms PA radar at high SNR.

Extraction of Doppler signature of micro‐to‐macro rotations/motions using continuous wave radar‐assisted measurement system

Mechanical–structural vibration and/or rotational parts of the targets will induce micro-Doppler frequency in addition to the main Doppler components. In the today's military era, detections, measurements and decision making have to be made after the thorough analysis of main and micro-Doppler signatures of the targets to get their full profile particularly for defence applications. In addition, few of the low radar cross-section targets can be detected only by extracting and processing the micro-Doppler signatures corresponding to the rotations of their propellant rotor blades. Therefore, experimental studies to measure the micro-to-macro rotation/motion generated Doppler frequency and performing its associated measurements become significant. The authors built a C-band (5.3 GHz) continuous wave radar and used it to measure the Doppler frequency generated by micro-to-macro rotations/motions. The detection and measurement accuracy of the developed radar is assessed by series of different open-environment experimental case studies: revolution per minute measurement of rotating blades, separation of multiple rotating blades, oscillation per minute measurement of a swinging pendulum, detection of approaching/receding motion and the Doppler signature extraction of walking/jogging/cycling person. All these measurement values are validated against the standard master instrument readings and theoretical calculations. Finally, the limitations of this system and required near-future research works to enhance its performance are listed.

Passive techniques for target radar cross section reduction: A comprehensive review

In this article, a comprehensive review of published techniques for reducing radar cross-section (RCS) of a target in various military and industrial applications is presented. This review contains the developments in this field over the last 24 years. In this comparative review, existing RCS reduction (RCSR) methods are categorized based on the type and the shape of their structures and their electromagnetic behavior and a variety of techniques of passive cancelation for RCSR is presented including the structures formed by both conductor and dielectric such as frequency selective surface, electromagnetic band gap, artificial magnetic conductor, different types of metasurfaces, polarization rotation reflective surface, and their combinations as hybrid techniques. A section is allocated for comparison in which a comprehensive comparison is drawn based on different characteristics of the structures, that is, the number and thickness of substrate layers, complexity and cost, RCSR bandwidth and level, their efficiency for TE and TM polarization, and their pros and cons. Moreover, the standard simulation and measurement setups and different kinds of optimization algorithms such as genetic algorithm, particle swarm optimization, and so on applied for RCS are presented and described. Finally, the conclusion, recommendations for future researches, and a trend of how the topic is possibly moving forward to overcome the main challenges are presented.

Demanded Dwell Time Reduction Based on Prior RCS Fluctuation Constraint in Target Tracking

In the field of airborne radar resource management, one of the most accessible solutions to enhance the power of modern radar system is to save target tracking time as much as possible. During the target tracking process, it is effective to utilize the prior knowledge of the radar cross section (RCS) of the target to save airborne radar resource. Since the target RCS is sensitive to frequency and attitude angle, it is difficult to predict the target RCS accurately. This paper proposes an effective way to save airborne radar time resource in the target tracking process by changing radiation frequency of airborne radar to tolerate certain RCS fluctuation. Firstly, based on the tolerable fluctuation range of the target RCS, this paper designs an effective search algorithm to minimize the frequency set while maximizing the average RCS within the limited fluctuation range. Secondly, the detection probability prediction phase is renewed by taking the RCS fluctuation into account in order to reduce the radar dwell time. Finally, by using interactive multiple model Kalman filter (IMMKF) algorithm, a target tracking procedure with the minimum dwell time prediction method is proposed. Simulation results show that the proposed method is effective. As for target tracking simulation of three different trajectories, the proposed method can save at best 81.35% more dwell time than the fixed frequency method.

클러터 환경에서 펄스 도플러 레이다 추적 초기화를 위한 신호 강도를 이용하는 RANSAC 처리 기법

We propose a RANdom SAmple Consensus(RANSAC) method using signal intensity for the track initiation of small target detection. The use of a low constant false-alarm rate threshold to detect a small radar cross-section target can cause numerous false alarms. Consequently, the optimal initialization of the target can be difficult. To solve this issue, we propose a sample-splitting RANSAC (S-RANSAC) method, which compensates for the accuracy degradation due to the lack of inlier data in the RANSAC. The key idea of our approach is to split the received plot data according to signal intensity. We compared the performance of the S-RANSAC method with those of a logic-based algorithm, the Hough transform, and the RANSAC method. Consequently, the S-RANSAC method demonstrated a better track initiation performance than the other methods under the given scenario.

Stochastic Geometry for Automotive Radar Interference With RCS Characteristics

With the widespread application of millimeter-wave (mmWave) radar technology in modern vehicles, vehicle-to-vehicle radar interference becomes a significant concern in exploiting the benefits of mmWave radar. This letter studies the radar mutual interference among vehicles on a practical bi-directional multi-lane road. Particularly, the fluctuation of the target radar cross-section (RCS) is modeled by Swerling I model and Chi-square model. Closed-form expression for successful ranging probability that works as the radar ranging performance metric is obtained by applying the stochastic geometry. Compared with constant RCS model in previous literature, the proposed performance metric based on random RCS models can provide more precise and intuitive results. The simulation results show that the increasing ranging distance and intensity of vehicles lead to a sharp decrease of the successful ranging probability.

Radar cross-section reduction by tunable low-pressure gas discharge plasma

In this experimental research, the effect of tunable low-pressure gas discharge plasma was examined on radar cross-section (RCS) reduction. A quintet array of plasma tubes (PAr = 10 torr, PHg ≈ 2–6 × 10−3 torr, Rin = 18 mm) next to each other was used to reduce the RCS of a planar metallic target. Plasma columns were optimized to have minimum axial and temporal inhomogeneity. The plasma electron density, plasma frequency, and collision frequency of the plasma tubes were measured by fast time-resolved microwave interferometry with simultaneous measurement of current and voltage. The influence of the discharge current (Irms = 50–1500 mA) as a regulator of the plasma parameters was investigated. RCS reduction changes were observed by tuning plasma parameters at a frequency range of 2–18 GHz for the normal and oblique incidence of TE and TM polarizations. The assembled plasma tubes depicted broadband RCS reduction (<−10 dB) in TM polarization for a 300 mA discharge current (42.5% total bandwidth) and in TE polarization for a 1400 mA discharge current (34% total bandwidth) for normal incidence. It was shown that the measurement is in good agreement with the simulation. It was concluded that by performing bistatic measurements, the plasma cylinders behave as a wave absorber and scattering object in the TE and TM polarizations, respectively.

MIMO Radar With Array Manifold Extenders

This article is concerned with the problem of multitarget parameter estimation in arrayed multiple-input multiple-output (MIMO) radar. In particular, the radar operates in the presence of moving targets, where the parameters of interests to be estimated for each target are the relative delay, Doppler frequency, direction-of-arrival (DOA) and complex path coefficients (or target's radar cross section). Using the novel concept of “array manifold extender,” the dimensionality of the observation space increases from $N$ to $N\mathcal {N}_{\mathrm{ext}}$ , making the radar more powerful than conventional MIMO radar systems by handling more complex targets and estimating their parameters with increased accuracy. Two “manifold extenders” are proposed in this article in conjunction with a novel spatiotemporal subspace-type framework for estimating the target parameters. The performance of proposed framework is examined using computer simulation studies.

Joint Adaptive Sampling Interval and Power Allocation for Maneuvering Target Tracking in a Multiple Opportunistic Array Radar System.

In this paper, a joint adaptive sampling interval and power allocation (JASIPA) scheme based on chance-constraint programming (CCP) is proposed for maneuvering target tracking (MTT) in a multiple opportunistic array radar (OAR) system. In order to conveniently predict the maneuvering target state of the next sampling instant, the best-fitting Gaussian (BFG) approximation is introduced and used to replace the multimodal prior target probability density function (PDF) at each time step. Since the mean and covariance of the BFG approximation can be computed by a recursive formula, we can utilize an existing Riccati-like recursion to accomplish effective resource allocation. The prior Cramér-Rao lower boundary (prior CRLB-like) is compared with the upper boundary of the desired tracking error range to determine the adaptive sampling interval, and the Bayesian CRLB-like (BCRLB-like) gives a criterion used for measuring power allocation. In addition, considering the randomness of target radar cross section (RCS), we adopt the CCP to package the deterministic resource management model, which minimizes the total transmitted power by effective resource allocation. Lastly, the stochastic simulation is embedded into a genetic algorithm (GA) to produce a hybrid intelligent optimization algorithm (HIOA) to solve the CCP optimization problem. Simulation results show that the global performance of the radar system can be improved effectively by the resource allocation scheme.

Edge Element Calculation of Radar Cross Section of Small Maritime Targets with Respect to Height of Radar Antenna

Edge Element Calculation of Radar Cross Section of Small Maritime Targets with Respect to Height of Radar Antenna

Metasurface-Based Method for Broadband RCS Reduction of Dihedral Corner Reflectors With Multiple Bounces

A broadband technique to reduce the radar cross section (RCS) of complex targets is presented. In such targets, multiple-bounce mechanism dominates their RCS. The proposed technique demonstrates that by treating the multiple-bounce mechanism as a cascaded phenomenon, the problem then simplifies to identifying and implementing a set of orthogonal functions. Robust guidelines for avoiding grating lobes are provided using array theory. The 90° dihedral corner is used to verify the proposed technique. Measurements are reported for a fabricated prototype with artificial magnetic conductor (AMC) technology where a 70% RCS-reduction bandwidth is observed. To generalize the method, a 45° dihedral corner, with quadruple-bounce mechanism, is considered. Generalized guidelines are summarized and applied to reduce the RCS of complex targets using the proposed method.

A Complete Automatic Target Recognition System of Low Altitude, Small RCS and Slow Speed (LSS) Targets Based on Multi-Dimensional Feature Fusion.

Low altitude, small radar cross-section (RCS), and slow speed (LSS) targets, for example small unmanned aerial vehicles (UAVs), have become increasingly significant. In this paper, we propose a new automatic target recognition (ATR) system and a complete ATR chain based on multi-dimensional features and multi-layer classifier system using L-band holographic staring radar. We consider all steps of the processing required to make a classification decision out of the raw radar data, mainly including preprocessing for the raw measured Doppler data including regularization and main frequency alignment, selection, and extraction of effective features in three dimensions of RCS, micro-Doppler, and motion, and multi-layer classifier system design. We design creatively a multi-layer classifier system based on directed acyclic graph. Helicopters, small fixed-wing, and rotary-wing UAVs, as well as birds are considered for classification, and the measured data collected by L-band radar demonstrates the effectiveness of the proposed complete ATR classification system. The results show that the ATR classification system based on multi-dimensional features and k-nearest neighbors (KNN) classifier is the best, compared with support vector machine (SVM) and back propagation (BP) neural networks, providing the capability of correct classification with a probability of around 97.62%.

Altitude ambiguity suppression method based on dual‐frequency interfering and multi‐frequency averaging for sparse baseline TomoSAR

Tomography SAR (TomoSAR) imaging can achieve three-dimensional (3D) imaging, which is significant for urban 3D mapping. When the baseline of TomoSAR is sparse, the scattering centres of several different altitudes in the same resolution unit are aliased together, which affects the accuracy of TomoSAR imaging. To solve this problem, an altitude ambiguity suppression method based on dual-frequency interfering and multi-frequency averaging is proposed. Firstly, dual-frequency interfering is used to obtain the radar cross-section (RCS) of targets and the sum of the results of the cross interference between targets and ambiguities in different positions. Then multi-frequency averaging is used to suppress the power of the cross-interference, and finally the RCS of target is accurately obtained. Simulation results verify the effectiveness of the proposed method.

RCS Historical Data Screening Method Based on Spatial Observation Geometric Relationship

Selecting accurate Radar Cross Section (RCS) sequence historical data has an important impact on RCS-based spatial target attitude anomaly detection. RCS is related to factors such as satellite shape size, attitude and radar observation angle, and is a sensitive function of observation angle variation. In this paper, the influence of spatial observation geometric relationship on spatial target RCS sequence is analysed. Aiming at the orbital regression characteristics unique to spatial targets, a spatial target RCS historical data screening method based on dynamic time programming (DTW) distance is proposed. According to the relationship between the azimuth and the elevation angles of the radar line of sight, the orbit data with similar spatial geometry is found from the historical data. The orbital data of the system. This method can reduce the impact of Earth’s rotation on data observation and establish a more efficient database. The variational mode decomposition (VMD) of RCS is carried out, and the fractal box dimension of each component is extracted as the data feature, and the BP neural network is used as the classifier for the anomaly detection. The simulation results prove that compared with the traditional historical data collection method, this method can improve the attitude detection rate of space targets and has better robustness.