Optimization of Three-Dimensional Multi-Shell Dielectric Lens Antennas to Radiate Multiple Shaped Beams for Cellular Radio Coverage

In this paper, a multi-shell spherical dielectric lens antenna is synthesized to radiate multi-beams with optimum shaped patterns for radio coverage at millimeter wave (mmW) frequencies. In particular, the design considers the composing characteristics of discrete multi-shell Luneburg lens antenna as an initial structure, and synthesizes its permittivity and sizes of dielectric shells to produce relatively shaped main beam patterns rather than conventional pencil-shapes. It targets to minimize inter-beam overlapping transition regions with slowly varying power density in the coverage boundary, and therefore reduce the ping-pong effect of inter-sector handovers to potentially minimize the inter-cell interferences arising from the over-large gain of pencil beam when the user equipment (UE) is at near the sector boundary far-off the beam peak. After the synthesis, the antenna is implemented at 38 GHz with both numerical simulation and measurement results shown to validate the concept. Successfully validation on the feasibility of beam synthesis in comparison to that of Luneburg lens antennas has been achieved. Discrepancy in fabrication to potentially result in slight radiation degradation is also discussed.