Design of Compact Rotman Lens Using Truncated Ports With Energy Distribution Slots

A compact Rotman lens is presented in this paper. The compact Rotman lens consists of a lens body and truncated ports with the energy distribution slots. By truncating the long triangular transitions of the traditional Rotman lens, the lengths of lens ports are reduced effectively. However, the impedance discontinuity problem is caused by truncating the triangular transition. To solve this problem, the energy distribution slots are designed between the feed lines and the truncated lens body apertures. The energy distribution slot is evolved from the 1-2 power divider, which creates a transition process for the wave energy propagating from the feed lines and realizes good impedance match between the lens body and the feed lines. To validate the proposed design, a 4x7 Rotman lens has been designed and prototyped at 10 GHz. The Rotman lens exhibits a scanning range of +/- 33 degrees, 27% bandwidth for VSWR < 2, and the isolation between beam ports better than 17.2 dB within the operation bandwidth. Basing on the advantages of compact size, low cost, easy processing, and wide bandwidth, the proposed compact Rotman lens may have wide applications in the multi-beam antenna systems.