A spectral domain ray tracing method for quasi-optical devices modelling

The spectral theory of diffraction (STD) is well known for its ability to deal with complex fields (creeping waves, shadow limit fields, caustics fields) and their transformations through multiple diffractions. We present a fully numerical and 3-D implementation of this method. This implementation is based on a ray-tracing representation of plane waves propagation and it takes advantage of the simplicity of the plane waves transformation formulas at dielectric or conducting interfaces. The geometrical optics ray-tracing part of the procedure is quite similar to what is done in the shooting and bouncing rays (SBR) method, which has been applied to scattering calculations. However, the final evaluation of the field is performed through a spectral domain integration in our spectral domain ray tracing (SRT) method, instead of a physical optics integration in the SBR method. We give an outline of the principles of the method, and present the application of the method to substrate-lens antenna analysis. Simulated results obtained through this method are compared to results obtained through a more classical physical optics analysis, and to measured far-field radiation patterns of the antenna.