Caustic Analysis of Reflected Rays from a Spherical Reflector Antenna

Now, 5G mobile system is developing to increase user capacity and reduce connection latency. At radio wave technology, new challenges such as millimeter wave (28GHz), small cell size and multi beam base station are introduced. At millimeter wave, where antenna size becomes small size of almost 30cm, a reflector antenna becomes promising. In order to use a reflector antenna for multi beam application, a spherical reflector is suitable. However, a spherical reflector has a problem of distributed caustics. In designing antenna, to clarify caustic positions is important. In this paper, the caustic position equation is derived. Accuracy of the equation is ensured by comparing with MATLAB simulation results. Finally, useful data for dual spherical reflector designing is obtained.