Dynamic Radar Cross Section Research Articles

Dynamic radar cross section similarity study based on dynamic time warping

Abstract Dynamic radar cross-section (RCS) represents the radar reflectance cross-section of an aircraft at different moments during flight and is a crucial criterion for evaluating the ability of a radar to detect an aircraft. In practice, it is challenging to construct an accurate 6-DOF dynamics model for the purpose of solving its dynamic RCS. Consequently, a 3-DOF dynamics model is employed for the analysis of dynamic RCS. This paper presents a methodology for the joint simulation of the dynamic RCS under two DOF models and subsequent comparison and analysis of the resulting sequence data via the dynamic time warping algorithm. It is also concluded that the dynamic RCS values calculated using the 3-DOF dynamics model can identify the target vehicle.

Viewing electromagnetic scattering characteristics on air-brake of a stealth plane

Purpose This study aims to learn the dynamic radar cross-section (RCS) of a deflection air brake. Design/methodology/approach The aircraft model with delta wing, V-shaped tail and blended wing body is designed, and high-precision unstructured grid technology is used to deal with the surface of air brake and fuselage. The calculation method based on multiple tracking and dynamic scattering is presented to calculate RCS. Findings The fuselage has a low scattering level, and the opening air brake will bring obvious dynamic RCS effects to itself and the whole machine. The average indicator of air brake RCS can be lower than –0.6 dBm2 under the tail azimuth, while that of forward and lateral direction is lower. The mean RCS of fuselage is obviously higher than that of air brake, while the deflected air brake and its cabin can still provide strong scattering sources at some azimuths. When the air brake is opening, the change amplitude of the aircraft forward RCS can exceed 19.81 dBm2. Practical implications This research has practical significance for the dynamic electromagnetic scattering analysis and stealth design of the air brake. Originality/value The calculation method for aircraft RCS considering air brake dynamic deflection has been established.

Dynamic Electromagnetic Scattering Simulation of Tilt-Rotor Aircraft in Multiple Modes.

To study the electromagnetic scattering of tilt-rotor aircraft during multi-mode continuous flight, a dynamic simulation approach is presented. A time-varying mesh method is established to characterize the dynamic rotation and tilting of tilt-rotor aircraft. Shooting and bouncing rays and the uniform theory of diffraction are used to calculate the multi-mode radar cross-section (RCS). And the scattering mechanisms of tilt-rotor aircraft are investigated by extracting the micro-Doppler and inverse synthetic aperture radar images. The results show that the dynamic RCS of tilt-rotor aircraft in helicopter and airplane mode exhibits obvious periodicity, and the transition mode leads to a strong specular reflection on the rotor's upper surface, which increases the RCS with a maximum increase of about 36 dB. The maximum micro-Doppler shift has functional relationships with flight time, tilt speed, and wave incident direction. By analyzing the change patterns of maximum shift, the real-time flight state and mode can be identified. There are some significant scattering sources on the body of tilt-rotor aircraft that are distributed in a planar or point-like manner, and the importance of different scattering sources varies in different flight modes. The pre-studies on the key scattering areas can provide effective help for the stealth design of the target.

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.

Modeling and Dynamic Radar Cross-Section Estimation of Chaff Clouds for Real-Time Simulation

Chaff is a passive jammer widely used to disrupt radar or radio-frequency sensors. A mass of chaff fibers dispersed in the air is commonly referred to as a chaff cloud. It is nearly impossible to numerically simulate in real-time the enormous amount of chaff fibers composing the chaff cloud. In this paper, we model the behavior of numerically estimated chaff clouds as probability density functions (PDFs) and apply approximation techniques to estimate the radar cross-section (RCS) of the chaff cloud in real time. To model the aerodynamics of the chaff cloud, we represented the combination of PDFs as functions of time and wind speed. The applied approximation techniques—vector radiative transfer and generalized equivalent conductor method—showed a computation time that cannot be achieved by low-frequency methods such as the method of moments or finite-difference time-domain. Moreover, the dynamic RCS results of the approximation techniques showed a similar trend to those of other studies simulating similar situations. The proposed scheme is effective for real-time chaff cloud simulation, and the modeled dynamics and estimated dynamic RCSs can be a standard baseline for developing new analysis methods for chaff clouds. In the future, the proposed scheme will extend to more chaff fibers and more diverse environmental parameters.

Dynamic sequential radar cross section properties of airborne corner reflector in array

AbstractWith the spread of airborne corner reflector (ACR) in the field of shipborne equipment, radar guided anti‐ship missile is facing new challenges. In order to achieve the mastery of the jamming principle of this apparatus, the paper studied its motion properties and sequential Radar Cross Section (RCS) properties. Firstly, the motion model of the ACR was obtained under certain constraints, by deriving the centroid dynamics equation and rotation dynamics equation according to the theoretical mechanics. Then, the dynamic sequential RCS model of ACR array was established by combining the motion model with the modified geometric optics method and coherent synthesis method. Through the simulation and analysis of the motion model, it was found that the flight process of the ACR can be divided into two stages: fast falling and steady falling. In the fast falling stage, the variables of the ACR system change rapidly, while the ACR rotates slowly and falls smoothly in the steady falling stage. From simulation of dynamic sequential RCS model, the results showed that the obvious depolarisation effect is occur in the fast falling stage. Further statistical analysis showed that, the omnidirectivity of single ACR is well from the dynamic perspective, meanwhile array placement can effectively enhance RCS amplitude and improve the probability density distribution.

A Dynamic RCS and Noise Prediction and Reduction Method of Coaxial Tilt-Rotor Aircraft Based on Phase Modulation.

For tilt-rotor aircraft with coaxial rotors (coaxial rotor aircraft), reduction of radar cross section as well as acoustic noise can be essential for stealth design, and the rotation of the coaxial rotors can have an influence on noise and dynamic radar cross section (RCS) characteristics. In this paper, an approach to the prediction of both the sound pressure level (SPL) of noise and the dynamic RCS of coaxial-tilt aircraft is carried out, based on the theories of the FW-H equation, the physics optics method (PO) and the physical theory of diffraction (PTD) method. In order to deal with the rotating parts (mainly including coaxial rotors), a generated rotation matrix (GRM) is raised, aiming at giving a universal formula for the time-domain grid coordinate transformation of all kinds of rotation parts with arbitrary rotation centers and rotation axis directions. Moreover, a compass-scissors model (CSM) reflecting the phase characteristics of coaxial rotors is established, and a method of noise reduction and RCS reduction based on the phase modulation method is put forward in this paper. The simulation results show that with proper CSM parameter combinations, the reduction of noise SPL can reach approximately 3~15 dB and the reduction of dynamic RCS can reach 1.6 dBsm at most. The dynamic RCS and noise prediction and reduction method can be meaningful for the radar-acoustic stealth design of coaxial tilt-rotor aircrafts.

Utilizing Dynamic Scattering for Learning Radar Cross-Section of a Flapping-Wing Aircraft

To study the radar cross-section (RCS) of a flapping-wing aircraft, a method of flapping-wing dynamic scattering is presented. The aircraft has two rigid wings and a fuselage similar to a bird’s body, where the plane shape of the wing is U-type. The aircraft model is established and the pitching and flapping actions of the wing are simulated. The electromagnetic scattering characteristics of aircraft under two flight modes, different radar wave frequencies and observation angles are investigated. The results show that in the given gliding mode, the fuselage provides the main contribution to the lateral peak value. For the given forward azimuth range in the flapping mode, increasing the azimuth can reduce the mean and peak of the aircraft dynamic RCS curve, while increasing the elevation angle will increase the peak and mean of the aircraft dynamic RCS curve. In the flapping mode, the mean RCS of the aircraft in the lateral backward azimuth is significantly lower than that in the lateral forward azimuth. For the given tail azimuth range, the increase of azimuth will increase the mean and peak level of aircraft dynamic RCS curve. The presented method is effective to study the dynamic RCS characteristics of the flapping-wing aircraft.

RCS Estimation of Drone Motion Using Mesh-Element Rotation in MoM and Micro-Doppler Signatures

For an automatic recognition system, a huge number of micro-Doppler signature images is required to train a classifier. However, in general, measurements are only possible for hovering drones, so the dynamic radar cross section (RCS) of a drone with various motions is estimated through EM simulation and converted into a micro-Doppler signature image. In this work, we use far-field approximation and mesh-element rotation in the method of moments to quickly estimate the dynamic RCS of a drone in various motions. First, 3-D meshes and the impedance matrix of a single propeller are generated only once. Instead of rotating the propeller, the position information of the mesh elements is rotated without recreating 3-D meshes or the impedance matrix. Next, using the mirror-image symmetric characteristics of drone propellers and the far-field approximation, the dynamic RCS of multiple propellers is synthesized from that of a single propeller. Finally, the dynamic RCS was estimated at 3 and 9 GHz and converted to micro-Doppler signatures, spectrogram, and cadence-velocity diagram (CVD). As a result, it was more accurate to estimate the dynamic RCS at 9 GHz, and it was easier to obtain the rotation frequency at 3 GHz in the CVD.

Influence of stealth aircraft dynamic RCS peak on radar detection probability

For modern stealth aircraft, it is important to analyze the influence of Radar Cross Section (RCS) peak exposure on penetration for guiding stealth design and penetration trajectory planning, which needs to reflect the RCS statistical uncertainty and the RCS difference with the change of incident angle. Based on the RCS characteristics of typical stealth aircraft, this paper established a simplified RCS dynamic fluctuation statistical model with the parameters log mean and log standard deviation. According to the detection probability algorithm in radar signal processing field, this paper built the algorithm of radar detection probability based on the RCS dynamic fluctuation statistical model. The analysis of examples concluded that the key to successful penetration is to shorten the RCS peak exposure time, which can be reduced by decreasing the RCS peak width or increasing velocity. Based on the conclusion, this paper proposed the method of turning maneuvering to reduce RCS peak exposure time dramatically.

Dynamic RCS Reduction Performances of Antenna Array with Coding Metasurface

On the basis of combining the two concepts of digital coding metasurface and metasurface antenna, low radar cross-section (RCS) coding metasurface antenna array with dynamic scattering performances is presented in this paper. Extending scattering factor theory to coding metasurface antenna, by controlling the states of PIN diodes randomly, the scattering performances of coding metasurface antenna array can be tuned dynamically without degrading its radiation property. Based on phase cancellation principle, a 8 × 8 antenna array was finally simulated and fabricated. By comparing several different layouts, taking checkerboard layout, new chessboard layout, and “0101” square ring nested layout as examples, both monostatic and bistatic RCS of the antenna mentioned above can be reduced 10 dB or more in the frequency range of 9–10.5 GHz under the illumination of x-polarized incident wave. The measured data are consistent with the simulation data, which proves the effectiveness of the proposed method.

Numerical investigations on radar cross-section of helicopter rotor with varying blade pitch

A calculation method is presented to study the radar cross-section (RCS) of the rotating rotor at different blade pitches. Based on blade pitch control, grid matrix transformation, and instantaneous RCS calculations, the electromagnetic scattering characteristics of the blade, rotor, and helicopter are obtained by the presented method. The pitch angle of each blade of the main rotor is regulated in fixed control mode, linear control mode and smooth control mode. The surface scattering characteristics of the blade in the fixed mode, the RCS of the blade and the rotor in the linear mode, and the effects of different control modes on the RCS of the rotor and helicopter are investigated. When the azimuth is 80°, the pitch of blade 1 is 9.6° in linear mode, and the RCS of some facets near the leading edge is reduced to −65 dBm2 under the given observation conditions. In the fixed control mode, the minimum period of the rotor RCS is equal to the basic passage time of the blade, while in linear control mode and smooth control mode, the minimum period of the rotor RCS is increased. Compared with the fixed control mode, the linear control mode can reduce the RCS peak of the helicopter at the given moment, and the smooth control mode is beneficial to reduce the RCS average of the rotor and helicopter at the given azimuth. The presented method is effective to analyze the dynamic RCS of the rotor and helicopter under different blade pitches, and has important engineering value for the stealth design of helicopter rotors.

The Effect of Turbulence on Dynamic Radar Cross Section of Chaff Clouds

Objective: This research reports the effect of turbulence on the dynamic Radar Cross Section (RCS) of chaff cloud. In the era of modern warfare technologies, most efficacious electronic countermeasure employed by the armed forces of various major powers is the Chaff. Chaff is based on the expulsion of numerous electrical dipoles of different length to cover the broad spectrum of radar frequency. This mechanism helps in deceiving the enemy missile by producing the required RCS. RCS of chaff cloud is a dynamic entity and rely on several aerodynamic factors. Methodology: Effects of turbulence on dynamic RCS are studied using Ansys Fluent for aerodynamic blooming simulation and Ansys HFSS for simulation of RCS of the bloomed chaff cloud. Findings: The subject of the paper corresponds to the significant effect of turbulence on the expeditious blooming of chaff cloud. The RCS of turbulent flow was higher by 1.5dBsm to 2.5dBsm for 50msec. The turbulence effect has reduced the blooming time of chaff filaments in the range of 25msec - 50msec. Novelty: Turbulence plays important role in faster blooming of chaff cloud and achieving minimum threshold RCS required for deception of RF seeker missiles. Keywords: Chaff; RCS; Turbulence; Modelling and Simulation

Analysis of Settling and RCS Response of Copper Coated Carbon and its Comparison with Aluminium Fibres

Background/Objectives: The present research focuses on comparative studies of two different type of chaff fibres for their effectiveness as electronics counter measure. Chaffs are electronic counter measures used in creating false radar signature to deceive tracking radar systems. Many types of chaff payloads are there in use, but the major one is aluminium fibres. These chaffs are designed to cover radar frequency range from 2-18 GHz. However, in future, tracking radars will operate in higher frequency range and will have improved algorithms to mitigate chaff noise of certain Radar Cross Section (RCS) threshold. Methods: The researcher used two different chaff fibres and their corresponding RCS are measured in anechoic chamber for their comparative study. Findings: It is observed that the RCS of the copper coated carbon (CuC) fiber is nearly equal to that of aluminium fiber but due their thinner diameter packing density of chaff fibres within a specified chaff cartridge volume has increased thus resulting in more number of dipole per chaff payload. Larger number of dipoles will help in improving dynamic RCS of chaff payload as it is directly proportional to the number of dipoles. Moreover, the terminal velocity of copper coated carbon fibres is lesser than that of aluminium fibres has improved the persistent time for CuCfiberwhich is a desirable parameter for the effective performance of chaff payload. Novelty: In order to increase dynamic RCS threshold one needs to increase chaff fiber density and chaff cloud suspension time. Both these can be achieved by the development of innovative thin CuCchaff fibres. In this paper, RCS of light weight and thin copper coated carbon chaff fibres were studied in comparison with traditional aluminium fibres and their advantages over aluminium fibres are reported. Keywords: Backscattered RCS; electrically conducting fiber; anechoic chamber; chaff; Settling Time

Dynamic RCS Estimation according to Drone Movement Using the MoM and Far-Field Approximation

Micro-Doppler signatures from the rotating propellers of a drone can be utilized to distinguish the drone from clutter or airborne organisms with similar radar cross section (RCS) levels, such as birds and bats. To obtain the micro-Doppler signatures of a drone, calculation or measurement of the electric field scattered from the rotating propellers is essential. In this paper, using the relative angle concept and far-field approximation, we propose a way to rapidly estimate the dynamic RCS of a drone with several propellers according to its movement. In addition, based on the fact that the shape of the propeller does not change even if it rotates, we construct an impedance matrix only once and apply the matrix to the method of moments instead of the iterative process of calculating the impedance matrix and inverse matrix for each rotation angle of the propeller. Finally, by using the Fourier transform of the results from the proposed method, the rotation frequencies of the propellers according to the movement of the drone can be obtained.

Effect of dual aircraft formation spacing on target position tracking on measurement conversion by monopulse radar

Aimed at the current problem of insufficient analysis of the influence of the diversified formation of dual aircraft on monopulse radar position tracking, the dual aircraft echo equivalent two point source jamming model is built. We designed the dual aircraft formation penetration movement scenario and three different formation spacings of 150, 250, and 350 m and extracted the dynamic radar cross section sequences of dual aircraft under different formation spacings. We established the dual aircraft formation equivalent scenario and calculated the dynamic signal-to-noise ratio and distance measurement accuracy of the radar received echo signals with different formation spacings. We fully considered the randomness characteristics of the phase difference of the actual dual aircraft echo and built the random angle error model of dual aircraft echo equivalent jamming. The distribution and random numerical characteristics of the random angular error are simulated and analyzed, and we combined the radar measurement conversion target position tracking algorithm to analyze the influence of different formation spacings on the monopulse radar tracking target position and position tracking accuracy. The simulation results show that a formation spacing of 350 m produces a greater randomness of angular error for dual targets, resulting in a greater dispersion of radar measurement traces, and the final average position mean square error is 132.8 m, which improves the position error by 15.6% compared with 150 m spacing.

Developing an innovative bimodal model to characterize the dynamic radar cross section of aircrafts

The distribution of aircraft dynamic radar cross section (RCS) varies at different course short-cuts and heights and can behave as a bimodal shape. Classical models, such as the Weibull distribution, the chi-square distribution, and lognormal distribution, fit poorly with bimodal RCS distributions and are unable to accurately describe the statistical characteristics of aircraft dynamic RCS. In order to overcome the shortcoming of the classical models, we propose an exponential polynomial distribution model as the probability density function for studying the RCS statistical characteristics. The model parameters were acquired through the linear least-square method. Based on the RCS statistical data, the proposed distribution model was validated through simulation experiments. We calculated the fitting error between the new model and the RCS statistical distribution and determined the optimal exponential polynomial distribution model. We then computed the coefficients of the determination to evaluate the proposed model. The Kolmogorov–Smirnov test showed that the proposed approach yielded smaller values compared to conventional distribution models. For all the analyzed cases, the exponential polynomial model can fit very well against the RCS distribution data with bimodal shape, and the fitting effect is significantly better than the results of the three classical models. The advantages of the proposed model are further demonstrated by comparing it with the Gaussian mixture distribution model from fitting error, determination coefficient, goodness-of-fit, mean error and variance error. The results suggest that the exponential polynomial distribution model provides a more effective alternative in describing the fluctuation characteristics of aircraft dynamic RCS at the different course short-cuts and heights. Given the advantages exhibited by the exponential polynomial distribution model in this study, the methodology and findings in this study can be used to improve in early warning detection of radar targets and as a theoretical basis to enhance the overall performance of radars. 2009 Elsevier Ltd. All rights reserved.

Keen Investigation of the Electromagnetic Scattering Characteristics of Tiltrotor Aircraft Based on Dynamic Calculation Method

To study the radar characteristics of the tiltrotor aircraft when considering rotor rotation and tilting actions, a dynamic calculation method (DCM) based on physical optics and physical theory of diffraction is presented. The results show that the radar cross section of a single rotor is dynamic and periodic when it rotates, while increasing the rotation speed can shorten this period. At a fixed tilt angle, the overall radar cross section of the cabin plus rotor still exhibits various dynamic characteristics at different azimuths when considering the rotation of the rotor. Increasing the tilt angle can better improve the electromagnetic scattering level of the rotor, but this easily makes the cabin and the outer end of the wing become a new source of strong scattering. In the heading direction, the dynamic radar cross section of the aircraft under a larger azimuth angle is lower when the cabin tilts from horizontal to vertical position. The presented DCM is feasible and effective to obtain the electromagnetic scattering characteristics of tiltrotor aircraft.

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.

Impact of cooperative jamming of dual stealth aircraft formation on detection performance of monopulse radar

To effectively test the detection performance of the monopulse radar under cooperative jamming of dual stealth aircraft formation, a blinking jamming model based on the interval of time-varying dual-aircraft formation is established for the first time in this study. By geometric modeling of the blinking jamming mode of the dual-aircraft formation, the authors solved the equivalent time-varying dynamic radar cross section of the penetration operation of the dual-aircraft formation; then, by taking the signal-to-interference ratio of the aircraft fuselage target echo in the actual formation as a parametric variable, we derived the equations for instantaneous detection distance, instantaneous detection probability, and cumulative detection probability of the monopulse radar in the formation projectile, and these equations were applicable to calculation under the actual jamming mode of dual-aircraft formation. Through simulation, the authors concluded for the first time that as the supersonic endurance speed increased, releasing jamming could reduce the radar detection probability considerably by more than 60%, while releasing projectiles could increase the formation’s risk of being detected by the radar by 30.37%. Thus, to effectively reduce the stability of the radar’s detection and tracking performance, the jamming power of the dual stealth aircraft formation should be no smaller than 0.5 kW and the signal gain of the formation should be no less than 20 dB.