Radar Cross Section Fluctuation Research Articles

RCS Modeling and Validation of Full Scale Launch Vehicle for its Real Time Dynamic Trajectory

Radar Cross Section (RCS) plays a significant role in detecting and tracking the space-based objects such as launch vehicles, missiles, aircrafts etc. In space applications, Radar systems are used to track and provide real-time trajectory information of the satellite launch vehicles after the lift off from the launch pad for range safety purpose. RCS is a critical key parameter that determines tracking performance of the Radar and it is highly dependent on both Radar operating parameters and the target characteristics. For space-based applications, a good quantity of RCS is required for quick detection by the Radar for continuous tracking. In order to choose the best Radar tracking configuration for real time tracking of the launch vehicle, it is required to model and simulate the launch vehicle’s RCS fluctuations prior to launch in order to predict the real time Signal to Noise Ratio (SNR) for its complete dynamic trajectory. This modeling and simulation methodology will help to choose the optimum Radar configuration for obtaining a good quantity SNR in the real-time launch. This study also provides good guidance to Radar operators for the effective Radar operation during real time space object tracking. This paper demonstrates, the real-time RCS fluctuations of a typical ISRO launch vehicle through simulation for its dynamic trajectory using physical optics based EM software prior to launch. Furthermore, the simulation results are validated with real time monostatic Radar tracking data, which showed good agreement.

Joint Power and Bandwidth Allocation with RCS Fluctuation Characteristic for Space Target Tracking

Reasonable allocation of space-based radar resources is a crucial aspect of improving the accuracy of space multi-target tracking and enhancing spatial awareness. The conventional resource allocation algorithm fails to exploit the high dynamic radar cross-section (RCS) characteristics, resulting in poor tracking robustness, tracking divergence, or even loss of tracking. However, the RCS of space targets fluctuates considerably in actual tracking scenarios, which cannot be disregarded for space target tracking tasks. To address this issue, we propose an adaptive allocation method that considers the dynamic RCS fluctuation characteristic for space-based radar tracking assignments. The proposed method exploits the predictable orbital information of space target to calculate the real-time observation angle of radar, and then obtains the multi-target dynamic RCS through the target RCS dataset. By combining the obtained RCS sequence, radar power, and bandwidth, an optimal model for radar tracking accuracy is established based on the multi-target posterior Cramér–Rao lower bound (PCRLB) to evaluate the tracking performance. By resolving the aforementioned multivariance optimization problem, we eventually acquire the results of power and bandwidth pre-allocation for tracking multiple space targets. Simulation results validate that, compared with the traditional methods, the proposed joint dynamic RCS power and bandwidth allocation (JRPBA) method can achieve superior tracking accuracy and minimize instances of missed tracking.

An Extended Robust Chance-Constrained Power Allocation Scheme for Multiple Target Localization of Digital Array Radar in Strong Clutter Environments

The traditional power allocation method for multi-target localization adopts the Robust Chance Constrained Power Allocation Scheme (RCC-PA), which does not consider the strong clutter characteristics in the current radar detection environment. However, how to reasonably allocate the power required for the radar to locate the target in the strong clutter is a fundamental challenge for improving the combat capability of the radar. Since Simultaneous Multi-beam Digital Array Radar (SM-DAR) can provide high-resolution information on targets in strong clutter, this paper extends the RCC-PA scheme to strong clutter and introduce an extended target model suitable for high-resolution SM-DAR. At the same time, the Gamma distribution is used to reflect the statistical characteristics of the Radar Cross Section (RCS) so that the extended RCC-PA scheme (ERCC-PA) can be suitable for all the scatterers whose RCS belong to Gamma distribution families. In the ERCC-PA scheme, the Strong Clutter Information Reduction Factor (SCIRF) of the extended target is first derived. Then, a Gamma Chance-constraint Programming Model (Γ-CCP model) is constructed to optimize the power allocation for locating multiple extended targets in strong clutter. The extended dichotomy method for power allocation is also given. Theoretical analysis shows that the power of multi-target localization in strong clutter can still be reasonably allocated under the target with multi-measurement characteristics. In addition, the power distribution of multi-target localization in the strong clutter is negatively correlated with the shape parameter of the Gamma distribution. Specifically, the larger the shape parameter characterizes the larger individual strong scatterer, resulting in the SM-DAR requiring less positioning power. The experimental results verify the theoretical analysis and show that the ERCC-PA scheme can improve the utilization of power compared with the benchmark and has the advantage of robustness to the fluctuation of the target RCS.

Y-type quadrotor radar cross-section analysis

PurposeThe purpose of his paper is to study the radar stealth performance of a Y-type quadrotor with coaxial rotors and parallel rotors.Design/methodology/approachThis Y-type quadrotor is designed as an aerodynamic layout with parallel twin rotors at the front and coaxial twin rotors at the rear. The multi-rotor scattering (MRS) method based on multi-rotor dynamic simulation (MRDS) and electromagnetic scattering module (ESM) is presented. MRDS is used to simulate the complex rotation of parallel rotors and coaxial rotors. ESM is used to calculate the instantaneous radar cross-section (RCS) of the quadrotor.FindingsFor a single rotor, the minimum period of the RCS curve at a given azimuth is equal to the basic passage time of the blade, where increasing the speed can shorten this minimum period. When the elevation angle increases, the forward RCS fluctuation of the quadrotor increases, while the average RCS decreases. The change of the roll angle will affect both the mean and the maximum difference of the RCS–time curve at the given lateral azimuth. The increase of the pitch angle will enhance the dynamic amplitude of the RCS–time curve under the forward azimuth.Practical implicationsThe research in this article can provide reference for the stealth design of the Y-type quadcopter in the future.Originality/valueThe originality is the establishment of the MRS method. This method could provide value for dealing with the electromagnetic scattering problem of coaxial rotors and parallel rotors.

RCS Measurement and Characteristic Analysis of a Sea Surface Small Target with a Shore-Based UHF-Band Radar

Effectiveness verification of weapon equipment and the selection of stealth material are inseparable from target radar cross-section (RCS) measurement. For RCS characteristic analysis of sea surface small targets, a fishing vessel was measured using a shore-based ultra-high-frequency (UHF) band radar. In this article, a full program of RCS measurement and characteristic analysis is presented, and three strategies are adopted to guarantee its high precision. For this, a scheme was designed for RCS dynamic measurement, along with the construction of a two-stage median filter to improve target positioning precision, and an RCS estimation procedure with sea clutter removal is elaborated upon, which increases RCS accuracy. Note that the test range satisfies the far-field criterion, and the multipath effect is modified by external calibration in our data. The measurement results reveal that the RCS level of the sea surface small target is sensitive to the aspect angle and wave height at a low grazing angle, but the RCS fluctuation characteristic is not. Therefore, the aspect angle and wave condition must be considered for sea surface small target detection, classification, or identification.

A Coherent Integration Segment Searching Based GRT-GRFT Hybrid Integration Method for Arbitrary Fluctuating Target

Long-time integration is an effective method for improving the signal–to–noise ratio (SNR) of an echo. However, if the target radar cross-section (RCS) fluctuates over the long integration time, the traditional coherent integration and noncoherent integration methods will produce significant performance losses, making it impossible to achieve a favorable integration performance at low SNRs. This study proposes a new hybrid integration method based on the generalized Radon–Fourier transform (GRFT) and generalized Radon transform (GRT) for targets with which echoes are partially coherent. First, a coherent integration is performed with GRFT within the optimal coherent processing segment using optimal coherent processing segmented matching. Then, the GRT is used for noncoherent integration between the coherent processing sections, and the target motion parameters are obtained through a global search. Compared with the GRFT, GRT, and moving target detection (MTD)-GRT methods, the proposed method applies to targets with arbitrary RCS fluctuations, arbitrary cross-range cells, and cross-Doppler cells, and offers the best detection performance. Finally, both simulation results and measured data processing results demonstrate the effectiveness of the algorithm.

Correlated Noncoherent Radar Detection for Gamma- Fluctuating Targets in Compound Clutter

This work studies the problem of radar detection of correlated gamma-fluctuating targets in the presence of clutter described by compound models with correlated speckle. If the correlation is not accounted for in a radar model, the required signal-to-interference ratio for a given probability of detection will be incorrect, resulting in over-estimated performance. Although more generally applicable, the is focus on airborne maritime radar systems. Hence K-distributed sea clutter is used as the main example. Detection via square-law non-coherent pulse integration is formulated in a way that accommodates arbitrary partial correlation for both target radar cross-section (RCS) and clutter speckle. The obstacle to including this degree of generality in previous work was the fact that Swerling's original characterization of the standard RCS fluctuation classes as gamma distributions for the power is not sufficient for the inclusion of both correlation sources (i.e.target and clutter speckle) for gamma-fluctuating targets. An extension of the model is required at the quadrature component (i.e. voltage) level, as phase relationships can no longer be neglected. This is addressed in the present work, which not only postulates an extended model, but also demonstrates how to efficiently compute it, with and without a number of simplifying approximation schemes within the framework of the saddle-point technique.

Z-folding aircraft electromagnetic scattering analysis based on hybrid grid matrix transformation

To study the electromagnetic scattering characteristics of a morphing aircraft with Z-folding wings, a method of hybrid grid matrix transformation (HGMT) is presented. The radar cross-section (RCS) of the aircraft in the four Z-folding modes is calculated and analyzed. When considering the deflection of the outer wing separately, the RCS of the wing under the head and side azimuth shows obvious dynamic characteristics, while the peak and fluctuation range are quite different. When the mid wing and the outer wing are deflected upwards together, the RCS of the aircraft under the positive side direction could be significantly reduced. When the mid wing deflects upward and the outer wing remains level, the peak of the side RCS of the aircraft is slightly reduced. When the mid wing deflects upwards and the outer wing deflects downwards, this peak indicator is further reduced, while the local fluctuation of the side RCS of the aircraft is increased. The HGMT method is effective to study the electromagnetic scattering characteristics of the Z-folding aircraft.

Следящая фильтрация показаний радиолокационной станции при обнаружении БПЛА

Unsanctioned intrusion of unmanned aerial vehicle (UAV) on the territory of the guarded object is primarily detected by specialized radio surveillance systems. The results obtained by radio surveillance systems are used for aiming of UAV visual identification and radio jamming systems. In this work, the problems of UAV detection and tracking of the target trajectory are considered. The known tracking filter systems for radio surveillance application were analyzed and a specialized matrix tracking filter system was proposed, which uses in its algorithm a dynamically changing energy potential of the radio surveillance system. The developed tracking filter system efficiency is evaluated using methods of matrix calculation, mathematical modeling, and probability theory. It has been established that the developed tracking filter system lets the radio surveillance equipment most effectively initiate trajectories of UAV, set its movement window, consider radio surveillance equipment characteristics, and approximate the trajectory of UAV at times of missed detections connected to radar cross-section fluctuations of moving targets. A high efficiency of the developed system has been achieved by decreasing the inaccuracy of the target position prediction two times in comparison with the known tracking filter systems. The obtained results allow easy scaling of the developed tracking filter system for its application as a part of any radio surveillance system.

PDF-ED-based adaptive waveform optimization for small slow target detection in strong clutter

This paper addresses the problem of small slow target detection in a strong clutter. By exploiting the characteristics of radar cross section fluctuation, the complex Gaussian procedure is utilized to model the matching filter output, introduce the Euclidean distance between the probability density functions (PDF-ED) to represent the resolvability of different hypotheses, and propose an adaptive waveform optimization algorithm that maximizes the PDF-ED between different hypotheses. Compared to the traditional ED between hypotheses, which only takes the mean value of the probability density into consideration, the PDF-ED metric considers the shape of the PDF curve and specifies the essential difference between two hypotheses in terms of information geometry. In this way, the proposed algorithm enhances the target and suppresses the clutter by reducing the side lobes at specified delay-Doppler units, resulting in the improvement of detection performance. The numerical experiments validate the effectiveness of the algorithm.

Multiple extended stealth target tracking from image observation based on non‐linear sub‐random matrices approach

The detection and tracking of extended stealth targets (ESTs) is a challenging task in radar technology, especially if from image observations because of the fluctuations of radar cross section. To overcome this challenge, multi-Bernoulli (MB) filter can be used to extract the extended target (ET) states in efficient and reliable manner. Recently, the MB-filter-based random matrices model (RMM) approach has been proposed for ellipsoidal ET tracking with additional state variables. However, RMM-MB filter is demonstrated with known detection profile, which is unsuitable for EST tracking. Thus, a joint detection and tracking of multiple ESTs based on track-before-detect (TBD) approach, which is an efficient way to track low-observable ESTs, is proposed. In EST-RMM-TBD scenarios, although the extension ellipsoid is efficient, it may not be accurate because of some missing useful information, such as size, shape, and orientation. To address this, a EST-sub-RMM-TBD composed of sub-ellipses is introduced, each representing an RMM. Based on such models, a sub-RMM-MB-TBD filter is used to estimate the kinematic states and extensions of sub-objects for each EST. Furthermore, a sequential Monte Carlo (SMC) implementation to estimate non-linear kinematic EST state is applied. The results indicate that the proposed SMC-sub-RMM-MB-TBD filter has more accurate cardinality estimation and smaller optimal sub-pattern assignment errors than the recent extended tracking filters.

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.

X-Band Radar Cross-Section of Tandem Helicopter Based on Dynamic Analysis Approach.

In order to study the radar signature of a tandem helicopter in the X-band, a dynamic analysis approach (DAA) is presented to determine its radar cross-section (RCS) under different influence factors. The basic passage time, rotation speed, observation angle, rotor disk inclination, fuselage attitude angle and Doppler feature are studied and discussed in detail. The results show that the dynamic characteristics of the rotor RCS will bring significant changes to the peak and average values of the helicopter RCS. Within a given observation angle range, a larger elevation angle is undesirable for helicopter stealth. The inclination of the rotor disc will affect the many small peaks and local fluctuations of the helicopter RCS. The positively increased attitude angle will have an undesirable effect on the average RCS and dynamic characteristics of the helicopter. The DAA is feasible and effective for studying the radar cross-section of a tandem helicopter.

Mixing Ratio Optimization of Chaff Elements for Wideband Jamming Using PSO

Chaff cloud is widely used in target covering. It contains huge numbers of chaff elements. An optimization method is presented in this letter for determining the mixing ratio of the chaff elements for wideband jamming. The electromagnetic scattering is calculated first for single chaff element with different lengths using the method of moments. Then, the superposition method is adopted to obtain the radar cross section (RCS) of the chaff cloud based on the scattering results of the chaff elements. Finally, the particle swarm optimization algorithm is used to determine the mixing ratio of the chaff elements to minimize RCS fluctuations within the jamming frequency band. Simulations show that the optimized chaff cloud can achieve good jamming performance over a wide frequency range.

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.

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.

Research on Ship Target Radar Scatttering Characteric Measurement in Sea Battlefield

Study on electromagnetic scattering related to ship target in the sea battlefield environment is always an important topic in radar seeker detection.。Dynamic measurement of radar cross section (RCS) of surface ship in outfield is an important means to obtain change in surface ship navigating and measurement environment and so on, the fluctuation of RCS is random and irregular. The statistic analysis for measurement RCS data in outfield of a certain ship is very important. In this paper, based on the airborne radar belong to Science and Technology on Electromagnetic Scattering Lab, the method of ship target measurement, It obtains the statistical distribution rule of ship’s RCS fluctuation. Compared the measured data with the numerical results, the similarity measure result shows a good agree. It shows that the measurement method is valid.

Assessment of monostatic broadband reflection characteristics of calibration trihedral corner reflectors with an allowance unorthogonal of their edges

The paper considers results of researches of influence of unorthogonal of edges of the trihedral corner reflectors (TCR) with triangular edges on changes of the maximum and median values of the radar cross section (RCS) within the central lobe of back scattering diagram (BSD) in wide frequency band. Fluctuations of RCS on frequency in radio frequency range are considered. Expressions for assessment of maximum deviation of results of calculation of RCS within the central lobe of BSD TCR with triangular edges caused by unorthogonal of their edges are presented. The received estimates of mean square deviation of the analyzed values for RCS TCR in working frequency band give the chance to compare the calculated values of RCS within the central lobe of BSD with results of electrodynamic modeling by method MoM taking into account reclining of their edges. These results can be used for the benefit of phonotarget information support of space means of arms and also when carrying out tests of samples of space arms. The provided scientific result gives the chance of assessment of RCS TCR RCS within the central lobe of BSD in wide frequency band with a margin error smaller, than at direct measurements of RCS.

전투기 레이다 측정 특성을 고려한 추적정확도 분석

This study analyzes the tracking accuracy(tracking errors) of fighter radar. Measurement error, detection failure, and radar cross section(RCS) fluctuation in radar measurements degrade the measurement quality and hence affect the tracking accuracy. Therefore, these radar measurement characteristics need to be considered when analyzing the tracking accuracy. In this paper, a method for analyzing the tracking accuracy is proposed; this method considers the detection error, detection probability, and RCS fluctuation. Results from experiments conducted with the proposed method show that the detection probability and RCS fluctuation affect tracking accuracy.

Robust Chance Constrained Power Allocation Scheme for Multiple Target Localization in Colocated MIMO Radar System

Taking into account the probabilistic uncertainty on the target radar cross section (RCS) parameter, a robust chance constrained power allocation (RCC-PA) scheme is presented for multiple target localization in colocated multiple-input multiple-output radar system. Such a system adopts a multibeam working mode, in which multiple simultaneous transmit beams are synthesized to illuminate multiple targets independently. We formulate the RCC-PA problem into a chance constrained programming model, where the total power consumption of the multiple beams is minimized to meet a specified multitarget localization accuracy requirement with high probability. Various target RCS fluctuation models have been discussed with different forms of probability distributions. We analytically show that the chance constrained programming problem for each RCS fluctuation model can equivalently be formulated as a deterministic convex optimization problem. Then, by formulating the Karush-Kuhn-Tuckers conditions, we transform the convex optimization problem into a nonlinear equation solving problem, and then solve it by using the bisection method. Simulation results show that our RCC-PA scheme can enhance the power utilization efficiency, and is more robust than the existing deterministic PA schemes.