Shooting And Bouncing Ray Method Research Articles

Fast Solution of Scattering and Micro-Doppler Features from Moving Target Using a Tailored Shooting and Bouncing Ray Method

In this paper, we present a tailored shooting and bouncing ray (SBR) method for the fast solution of electromagnetic (EM) scattering from a moving target. And, the micro-Doppler features of the moving target are investigated using a time-frequency analysis technique. In our method, a dynamic spatial division technique is employed to accelerate facet information processing and ray-tracing progress of the moving target. At first, the two coordinate systems are established, which are the geodetic coordinate system (GCS) and the local coordinate system (LCS). In GCS, the target is moving with translation and rotation. The dynamic spatial division is established in LCS to store the facet information and remain relatively stationary to the target. In comparison with the traditional SBR method, this technique avoids repetitive spatial division at each moment in the GCS. Then, ray tracing is performed to find the illuminated facets in the LCS. Finally, the scattering field and the phase compensation are computed in the GCS. In numerical simulations, the verification and computation efficiency comparison are provided using our method and other solutions (MLFMM, RL-GO, and traditional SBR). Moreover, the micro-Doppler features are extracted and analyzed using the time-frequency analysis technique, which includes the precession and spin of the missile, and the rotation of the aircraft. Meanwhile, the micro-Doppler spectra of the target is also compared with the theoretical Doppler of equivalent strong scattering points, which are obtained using the instantaneous high-resolution range profile (HRRP).

A Model for Calculating Electromagnetic Scattering From Target in Evaporation Duct

In this letter, we proposed a new model to solve the scattering problem from target in evaporation duct. First, the traditional two-dimensional (2-D) subsection ray tracing (SRT) method is extended to 3-D case. Then the 3D SRT is used to obtain the propagation direction and attenuation of the transmitted electromagnetic wave from antenna. Second, shooting and bouncing rays (SBR) is used in the simulation of complex target scattering. Different from traditional SBR, the launched rays are not planed wave. A virtual transmitting plane is established to obtain the amplitude and direction of these rays in evaporation duct in front of the target. The transmitting plane in evaporation duct can be regard as the incident field of SBR method. What's more, the new model based on SBR is accelerated by CUDA and OptiX from Nvidia to deal with the tremendous number of rays. Finally, the scattering EM field and power distributions in evaporation duct environment are calculated and discussed in the last section.

An Accelerated SBR Method for RCS Prediction of Electrically Large Target

This letter proposes an improved shooting and bouncing ray (SBR) method to efficiently predict the radar cross (RCS) of electrically large targets. First, the scan line algorithm is used to convert three-dimensional (3-D) processing to the 2-D graphic display, which expedites the elimination of shadows. Then, the ray tracing process is accelerated by the ray-marching technique which greatly decreases the intersection test. The validity of the proposed method is verified by comparing the simulation results with those of the multilevel fast multipole method. The runtime performance contrast of the traditional Octree-SBR method and ours indicates that the accelerated algorithm is more computationally efficient. Therefore, the presented algorithm has an excellent performance in the RCS prediction of electrically large targets.

An Accelerated Shooting and Bouncing Ray Method Based on GPU and Virtual Ray Tube for Fast RCS Prediction

An accelerated shooting and bouncing ray (SBR) method is presented in this letter to improve the efficiency of radar cross section prediction for electrically large and complex objects. The SBR method is inefficient because it needs to trace a large number of ray tubes. Therefore, its efficiency can be improved by reducing the amount of ray tubes and increasing the speed of ray tracing. In this letter, we use rays instead of ray tubes to reduce the amount of rays that need to be traced, and construct a virtual ray tube at the ray exit position for field integration. Moreover, ray tracing and integration operations are executed on the graphics processing unit to further improve the efficiency of SBR method. Several examples are designed to prove the effectiveness of the proposed method.

Acceleration of shooting and bouncing ray method based on OptiX and normal vectors correction.

The present paper deals with a new efficient shooting and bouncing ray (SBR) method based on OptiX and normal vectors correction. The basic idea is to make full use of the computing resources of the RTX series graphics cards. For ray tracing, the algorithm uses OptiX to invoke the built-in RT Cores of hardware. Thus, a fast intersection test can be implemented. To reduce the error of ray tracing caused by the facetted surface characterizing the curved surface, the direction of the reflected ray is corrected by normal vectors correction. Additionally, multiple GPU cores are invoked to accelerate the calculation of far-field integration of millions of ray tubes, which can improve the efficiency of the algorithm while reducing the data transmission time of heterogeneous devices. Simulation results show that the ray path after normal vectors correction is consistent with the theoretical results, and the algorithm can predict the RCS of arbitrary facetted geometries, which is 60 times faster than the SBR method based on kd-tree.

An Improved Ray-Tracing Algorithm for SBR-Based EM Scattering Computation of Electrically Large Targets

We put forward an improved ray-tracing algorithm to obtain a fast prediction of the radar cross section (RCS) for electrically large complex targets using the shooting and bouncing ray (SBR) method. Our algorithm employs a rope-based kd-tree data structure together with the neighbor-facet-tree based backward ray-tracing technique. The proposed algorithm shows excellent performance in the evaluation of scattering properties of the electrically large targets at high frequency. To assess and validate the proposed method, we compute the RCS of electrically small targets and of a realistic aircraft model and compare results with those of the traditional SBR method and multilevel fast multipole method. The agreement of the results together with the runtime performance demonstrate the accuracy and efficiency of our method.

A Space-Mapping-Based Optimal EM Design of RCS Reduction for Electrically Large Targets

An efficient electromagnetic (EM) optimization technique for radar cross section (RCS) reduction is proposed to achieve stealth. At first, two optimization models, namely coarse and fine models, are constructed to describe the scattering problem. More specifically, the coarse model of shooting and bouncing ray (SBR) method provides worse accuracy results than the fine model of the method of moment (MoM). However, less computational resources are needed for the coarse model when compared with the fine model. Then the SBR method is implemented into the Hummingbird optimization algorithm to obtain the solution of the coarse model. Third, the solution of the coarse model is verified for the fine model by using the MoM. Noted that the impedance boundary condition is applied to accelerate the calculation. At last, the trust region aggressive space-mapping (TRASM) algorithm is used to find the optimal solution between the SBR and MoM methods. By building the mapping relationship between these two models, the optimization efficiency can be significantly improved with high accuracy. Numerical results are given to demonstrate that the proposed optimization technique can be used as a fast tool for the cloaking design of RCS reduction. It is found that the RCS can be reduced largely by using the proposed optimization technique.

Advancing Accuracy of Shooting and Bouncing Rays Method for Ray-Tracing Propagation Modeling Based on Novel Approaches to Ray Cone Angle Calculation

We propose and evaluate several improvements to the accuracy of the shooting and bouncing ray (SBR) method for ray-tracing (RT) electromagnetic modeling. We propose per-ray cone angle calculation, with the maximum separation angle between rays calculated for every individual ray, based on a set of local neighbors rather than a single global maximum. This allows the smallest theoretical error of the SBR method, adaptive ray spawning procedures, and a unique analysis of the effect of ray cone sizes on the accuracy of the method. For the conventional uniform angular distribution of rays, a less general and versatile but more expeditious approach, we derive an analytical expression for the optimal choice of cone angle to again maximize the overall accuracy of the SBR computation. Both approaches are derived using icosahedral ray spawning geometry and adjacent ray sets, which are also used for our double counted rays identification and removal technique that avoids complicated ray path searches. The results demonstrate that the advanced shooting and bouncing RT method--using both proposed ray cone generation approaches--can perform wireless propagation modeling of tunnel environments with the same accuracy as image theory RT, a dramatically less efficient but traditionally considerably more accurate solver.

Study on Composite Electromagnetic Scattering Characteristics of Low-Altitude Target Above Valley Composite Rough Surface Using Hybrid SBR-EEC Method

The composite electromagnetic (EM) scattering characteristics of low-altitude target above valley composite rough surface are studied. The composite rough surface modeling theory is adopted to simulate the natural cavity structure of valley environment. Aiming at efficiently and accurately calculate the composite EM scattering from low-altitude target above valley environment, a hybrid method combining shooting and bouncing ray (SBR) technique and equivalent edge currents (EEC) method is proposed, in which SBR method based on the ray-density normalization (RDN) is applied to consider the multiple interactions between target and environment, and EEC method meliorates target's edge diffraction. Numerical examples illustrate the efficiency and validation of proposed hybrid method. Finally, based on the hybrid SBR-EEC method, the EM scattering characteristics of low-altitude target above valley environment are further investigated to show scattering mechanisms of this composite model and provide some useful conclusions through physical phenomena.

Comparison of SBR and MLFMM techniques for the computation of RCS of a fighter aircraft

In this work, an extensive correlation between two commonly used radar cross-section (RCS) computation techniques, i.e. shooting and bouncing rays (SBR) and multilevel fast multipole method (MLFMM), is performed. Numerical results are compared with the measured data, obtained from an anechoic chamber, for a 1:8 scaled down model of a fighter aircraft. It is ascertained that the SBR method, notwithstanding its numerical simplicity, can provide qualitatively similar and reasonably accurate RCS results for an object of varying complexity.

A high precision shooting and bouncing rays method without mesh for scattering calculation of complex target

AbstractTo extend the application of shooting and bouncing rays (SBR) method in the penetration structure and further improve the calculation accuracy, an improved mesh free SBR method that completely implements ray‐tracing and electromagnetic computing in 3‐D geometrical modeling software is proposed. The basic idea is to combine the non‐uniform rational b‐splines (NURBS) surface modeling function and open application programming interface (Open API) to implement the process of mesh free ray tracing, which greatly improve calculation accuracy and efficiency of SBR. Based on this, the improved SBR method can yield a superior performance for scattering analysis of complex targets, especially at the problem where reflected and transmitted waves exist simultaneously in a target. The numerical results demonstrate that the improved SBR is highly effective in computing scattering fields of complex targets.

An Accelerated SBR for EM Scattering From the Electrically Large Complex Objects

In this study, an accelerated shooting and bouncing ray (SBR) method was proposed to improve the computational efficiency of electromagnetic (EM) scattering from the electrically large complex objects. Initially, an open graphics library was employed to speed up the shadow faces removal. Then, the neighbor search technique was utilized to accelerate the ray tracing process, which was different from traditional SBR based on the traversal algorithms of Octree. The validation of the proposed method was verified by comparing the simulation results with those of the FEKO multilevel fast multipole method. Moreover, the EM scattering from two electrically large complex ship models was analyzed, and a desirable acceleration ratio was achieved. Therefore, the accelerated SBR method yields a superior performance for scattering analysis of electrically large complex targets, especially at high frequency.

SBR Method for Near-Field Scattering of an Electrically Large Complex Target Illuminated by Dipole Sources

An accurate and efficient physical-optics (PO) near-field integral representation is proposed and introduced into shooting and bouncing ray (SBR) to evaluate the electric and magnetic near-fields scattered from electrically large complex objects illuminated by dipole sources. The PO near-field integral expressions can be reduced to closed-form expressions by applying locally expanded phase approximations and surface partitioning. By introducing the proposed PO near-field integral expressions, SBR can be used to solve near-field scattering problems from electrically large complex objects. Simple and complex numerical examples are presented to demonstrate the efficiency and accuracy of the proposed method.

The Algorithms for the Ray Tracing Based on the Analytical Solutions

We consider the problems of ray tracing faced when calculating the parameters electromagnetic field in ray approximation. The Shooting and Bouncing Rays (SBR) model is characterized briefly and the disadvantages of its software implementations are specified. The alternative model for ray tracing at flat obstructions is presented using the analytical solutions obtained by means of analytic geometry. The introduced model allows us to avoid the redundant computations that the SBR method requires and, therefore, we can reduce time needed for the tracing tasks solution. The new algorithms for ray tracing after reflection and diffraction are stated and the possibility of their software support studied.

An Improved Backward SBR-PO/PTD Hybrid Method for the Backward Scattering Prediction of an Electrically Large Target

An improved hybrid method of backward shooting and bouncing ray (SBR) physical optics (PO)/physical theory of diffraction (PTD) is proposed to investigate the backward scattering from a three-dimensional electrically large target. The basic idea is to combine the forward-ray-tracing technique to accelerate the original backward-ray-tracing one. The proposed method significantly reduces the computational complexity while ensuring the same computational accuracy with the traditional backward SBR method. The accuracy and performance of our method are validated and evaluated by comparison with the exact computational electromagnetic method (FEKO-MLFMM) and experimental data for electrically small targets. The last case for the warship model illustrates that our method can enable good speedup for electrically large complex objects.

PARALLEL SHOOTING AND BOUNCING RAY METHOD ON GPU CLUSTERS FOR ANALYSIS OF ELECTROMAGNETIC SCATTERING

This paper proposes an e-cient parallel shooting and bouncing ray (SBR) method on the graphics processing unit (GPU) cluster for solving the electromagnetic scattering problems. At each incident direction, the parallel SBR method partitions the virtual aperture into sub-apertures, and distributes the computational process of each sub-aperture over GPU nodes. As ray tubes in the virtual aperture do not have the same computational time, the parallel e-ciency highly depends on how to partition the virtual aperture. This paper addresses this issue by a dynamic partitioning scheme according to the computational time at the previous angle, which can achieve excellent load balance. Numerical examples are presented to demonstrate the accuracy, high parallel e-ciency, good scalability and versatility of the proposed method.

Novel usage of binary tree in SBR algorithm for efficient indoor propagation analysis

This letter proposes new usage of the binary tree constructed by fundamental GO ray components in shooting and bouncing rays (SBR) for indoor propagation analysis. The node number of the binary tree is here considered as an important parameter. A couple of small size arrays that can store the passing ray information of both the node number and the position of the pixel considered, and the corresponding ray classification algorithm are newly introduced, not to double-count the same ray with slightly different bouncing angle. Consequently, we realize the big reduction of the computer memory resources consumed for the ray classification especially for wide area analysis, keeping the high accuracy of the SBR method.

Adaptive Aperture Partition in Shooting and Bouncing Ray Method

The shooting and bouncing ray (SBR) method may give rise to a divergence problem when ray tubes intersect discontinuous parts of the target, such as the boundary, and this affects the accuracy to some extent. This paper proposes an adaptive aperture partition algorithm to solve this problem. The proposed algorithm adaptively splits the virtual aperture into continuous irregular beams instead of discrete uniform ray tubes according to the geometry of the target during the recursive beam tracing. These beams form a beam tree, the level of which represents the number of reflections. Geometric optics is applied to the representative propagation path of each leaf beam to obtain the exit field, and then physical optics is used to evaluate each leaf beam's scattered field. The proposed algorithm could generate the convergent solution of the SBR method when the ray-tube size tends toward infinitesimal. Additionally, this paper describes the beam-triangle intersection in detail and utilizes the kd-tree to accelerate the beam-target intersection. Numerical experiments demonstrate that adaptive aperture partition can greatly improve the accuracy of the SBR method, and the computational efficiency can be also significantly enhanced in several applications, such as the RCS prediction in the THz band.

An improvement for the acceleration technique based on monostatic bistatic equivalence for shooting and bouncing ray method

An efficient algorithm is present for improving the acceleration technique of the monostatic radar cross section (RCS) prediction based on monostatic bistatic equivalence principle for the shooting and bouncing ray (SBR) method. Using the monostatic bistatic principle, the time consumed by the monostatic RCS simulation can be greatly reduced since the ray tracing procedure of the SBR method is avoided for a lot of incident angles. However, the result of the monostatic RCS using the monostatic bistatic equivalence get worse in the case of multiple bounces in ray tracing. To remedy this disadvantage, parts of rays are chosen with a sophisticated algorithm to be traced in order to correct the phase and location of the ray tubes. Numerical results demonstrate that the present algorithm is efficient for the SBR method in analysis of electrical large objects. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1178–1183, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25892

A hybrid SBR/MoM technique for analysis of scattering from small protrusions on a large conducting body

A hybrid technique combining the shooting-and-bouncing-ray (SBR) method and the method-of-moments (MoM) is presented for analyzing scattering by large conducting bodies having small protrusions. In this technique, the MoM with an approximate Green's function is used to characterize the small protrusions, yielding an admittance matrix, which, when multiplied with the incident field on the protrusions, yields the currents induced on the protrusions. The incident field in the presence of the large bodies is calculated using the SBR method. The field radiated by the currents on the protrusions is also calculated using the SBR method with the aid of reciprocity. Furthermore, an iterative approach is developed, which can reduce the error introduced by the use of the approximate Green's function, Numerical results are given to demonstrate the accuracy and capability of the hybrid technique.