Multibeam plane array using modified Butler matrix circuits

An antenna array with multibeam is proposed with modified Butler phase shift network. The array is made up with four omni-direction antennas. Its pattern can be controlled by changing feeding port. It can completely cover horizontal surface. Direction resolution is 90 degree, and can be improved to 45 degree if distribution network is used. This kind of array can be used for base station or in approximate estimation of DOA.