Asymmetric Ground Rotman Lens for Multilayer Packages

An asymmetric ground Rotman lens is presented in this letter. A new design of a Rotman lens is proposed to accommodate a whole beamforming system by providing separate ground layers for antennas and circuits. The lens has three dielectric layers and four metallic layers. The prototype of the lens consists of seven array ports, five beam ports, and six dummy ports. The measured return losses show that all the beam ports are matched to better than 12 dB in the band of interest from 23 to 25 GHz. The radiation patterns were measured in a near field measurement system. It shows that the beam directions are -25^°, -13.6^°, 0.2 ^°, 12.4 ^°, and 24.5 ^°, respectively and the beam widths are 14 ^°, 13.8 ^°, 13 ^°, 13.4 ^°, and 14.1 ^°, respectively. These results are in good agreement with the simulation. Thus, it is verified that the asymmetric ground lens is one of the best solutions for a compact beamforming system.