Radiation patterns from substrate-lens antennas: a method of analysis for THz application

This paper summarizes a spectral domain ray tracing (SRT) method for modeling substrate-lens antennas radiation patterns. An original rigorous and 3-D combination of Plane Wave Spectrum (PWS) decomposition of fields and Geometrical Optics is performed and implemented to model quasi-optical devices and in particular substrate-lens based antennas. Basic advantages of this method are: 1- Internal reflections inside the lens are taken into account, 2The lens surface can be either in the near field or in the far field of the antenna, and 3- The method can be applied to model a given structure for a very wide frequency range. It is shown that results converge as the number of internal reflections is increased. The simulation results are compared with Physical Optics (PO) results in the case where the lens surface is in the far-field of the antenna (the only acceptable case for the PO analysis).