Abstract-In this paper, an antenna-mode-switch technique is proposed to reduce the array size for the DOA (direction-of-arrival) estimation. Conventional DOA estimation requires many elements of antenna array to achieve high resolution, and then suffers from large array size. To improve such disadvantages, this paper proposes an antenna-mode-switch technique to reduce the required number of array elements. Our results show that the required number of array elements will be greatly reduced by using the proposed technique. Furthermore, a bow-tie antenna design for implementing the proposed antennamode-switch technique is also proposed. The results prove that highresolution and accurate properties of such a practical antenna design is very close to those of the ideal antenna mode.