Planar Multibeam Array Antenna with Rotman Lens Beamformer for 5 GHz Band Wireless Applications

A planar multi-beam array with a co-planar Rotman lens beamformer is introduced for wireless applications. The array consists of 8 linear series-fed subarrays with proximity-coupled patch elements. The Rotman lens feeds the subarrays through coupling slots. To reduce beam squinting, the subarrays are fed from the center. The coupling slot feeds each arm of a subarray 180° out of phase. To compensate out-of phase feeding, two feeding arms of each subarray are designed in the opposite direction. Also, cross-polar radiation is reduced significantly. In order to reduce the size of radiating patches to fit within array cell size, they are formed by four sub-patches with indentions and are fed by microstrip line from feed layer with two matching sections to improve the bandwidth. Measured results of the array structure in terms of the S-parameter of beam ports and radiation patterns are presented.