Multibeam antenna having auxiliary antenna elements

摘要

A multibeam antenna for forming multiple beams includes an antenna array and a Butler-matrix feeder circuit. The antenna array is composed of 2n main antenna elements and a group of 2n or less auxiliary antenna elements placed at either one or both sides of the main antenna elements. Antenna power is supplied to the antenna array from the Butler-matrix feeder circuit and is distributed to all the antenna elements with higher power to the elements located in the middle of the array and lower power to the elements located at sides of the array. Phase of the power supplied to the main antenna elements is shifted by 180-degree, and the phase-shifted power is distributed to predetermined auxiliary antenna elements. Thus, sidelobes associated with antenna beams are reduced and the beam directivity is improved.