Realistic source modeling and tolerance analysis of a luneburg lens antenna

This paper presents an accurate method for optimization of the lens-feed horn antenna based on realistic source modeling, the standard spherical wave expansion (SWE), and the genetic algorithm (GA). The realistic source modeling is achieved by calculation of the equivalent electric and magnetic currents at the horn aperture using CST MWS and then expanding the field in the SWE. Excellent agreement was achieved between the radiation patterns calculated using the SWE method and CST MWS for both a conical horn and the lens-horn antenna. Further, the effect of tolerances of dielectric permittivities on the gain and sidelobe levels was examined. It was shown that the variation of dielectric permittivities within the range of ±3% may significantly reduce the gain. The highest gain loss is obtained if the variation of the dielectric permittivities for the inner layers and outer layers have opposite signs (i.e. +/-). The gain loss may be compensated for by adjusting the feed location, however the sidelobe levels become higher than for the optimized lens. For applications requiring low sidelobe levels higher accuracy of dielectric permittivities may be necessary.