Spherical Luneburg lens antennas: engineering characterizations including air gap effects

The performance of the spherical Luneburg lens with varying parameters such as air gaps, size, number of shells has been investigated with a previously developed full 3D code utilizing the eigenfunction expansion method. With the fixed size lens, the gain increases as the number of shells increases. However, it has been shown that the gain rapidly drops as the air gap increases with a large number of shells. Also, the side-lobe levels are shown to be higher with larger air gaps or with a fewer number of shells. The near-field patterns help understand the collimating actions of Luneburg lenses associated with various parameters.