The shooting and bouncing rays (SBR) method in
computational electromagnetics
Computational electromagnetics (CEM), computational electrodynamics or electromagnetic modeling is the process of modeling the interaction of electromagnetic fields with physical objects and the environment.
It typically involves using computer ...
was first developed for computation of
radar cross section
Radar cross-section (RCS), also called radar signature, is a measure of how detectable an object is by radar. A larger RCS indicates that an object is more easily detected.
An object reflects a limited amount of radar energy back to the source. ...
(RCS). Since then, the method has been generalized to be used also for installed antenna performance. The SBR method is an approximate method applied to high frequencies. The method can be implemented for
GPU computing
General-purpose computing on graphics processing units (GPGPU, or less often GPGP) is the use of a graphics processing unit (GPU), which typically handles computation only for computer graphics, to perform computation in applications traditiona ...
, which makes the computation very efficient.
Theory
The first step in the SBR method is to use
geometrical optics
Geometrical optics, or ray optics, is a model of optics that describes light propagation in terms of '' rays''. The ray in geometrical optics is an abstraction useful for approximating the paths along which light propagates under certain circumsta ...
(GO,
ray-tracing) for computing equivalent currents, either on metallic structures or on an exit aperture. The scattered field is thereafter computed by integrating these currents using
physical optics (PO), by the
Kirchhoff's diffraction formula Kirchhoff's diffraction formula (also Fresnel–Kirchhoff diffraction formula)
can be used to model the propagation of light in a wide range of configurations, either analytically or using numerical modelling. It gives an expression for the wave ...
. The current
on a perfect electrical conductor (PEC) is related to the incident magnetic field
by
. This approximation
holds best for short wavelengths, and it assumes that the radius of curvature of the scatterer is large compared to the wavelength.
Extending SBR for edge diffraction
Since the approximation described above assumes that the radius of curvature is large compared to the wavelength, the
diffraction from edges needs to be handled separately. The SBR method can be extended with physical theory of diffraction (PTD) in order to include edge diffraction in the model.
Implementation in commercial software
The SBR method is implemented in the following commercial codes:
* Altair Feko (method there known as RL-GO - Ray Launching Geometrical Optics)
* CST Microwave Studio, Asymptotic Solver
* Ansys HFSS SBR+, previously Delcross Savant
* XGTD
See also
*
Computational electromagnetics
Computational electromagnetics (CEM), computational electrodynamics or electromagnetic modeling is the process of modeling the interaction of electromagnetic fields with physical objects and the environment.
It typically involves using computer ...
References
{{reflist
Geometrical optics
Antennas (radio)