Design of multi-beam antenna based on Rotman lens

A planar Rotman lens antenna that generates multiple beams is presented over a wide angular range. The proposed multi-beam antenna consists of a Rotman lens and a ten-element printed Yagi antenna array. By properly comparing optical aberrations, expressing as the normalized path length errors l, the suitable ratio of on-axis to off-axis focal length (g=G/F) is acquired so as to minimize phase errors for the array elements. Ten dummy ports are employed to reduce the performance deterioration caused by energy reflection. A prototype with seven input ports was fabricated and measured, covering a wide scanning angle of 60 degrees (-30 degrees, 30 degrees). The measured beam patterns show that the seven beam gains are distributed from 11.9 to 13.6 dBi under operating of 8.15 GHz. Both the simulated and measured results are used to verify the design approach.