A planar sector antenna for indoor high-speed wireless communication terminals

Wide-band digital indoor communication systems, such as wireless LANs and wireless ATMs, are being developed in the quasi-millimeter and millimeter wave frequency bands. In such high-speed systems, the degradation of transmission quality by multipath fading is a significant problem. Since wireless communication users operate their terminals without knowing the direction of the other station, the antennas should cover all directions with narrow beams. In addition, the antenna gains should be equalized in all directions. A sector antenna consists of narrow beams radially oriented and the beams are electrically switched to select the best signal. Therefore, its hardware is not complex and control is fairly simple. This paper shows a new methodology for realizing planar sector antennas. The sector antenna uses two kinds of beams formed by two kinds of antennas: planar 4-beam subarrays and planar single-beam subarrays. In order to equalize the antenna gains in all sectors, the beam shapes are carefully designed to offset the movement experienced by portable terminals. The 4-beam subarray is a multi-beam antenna integrated with a planar Butler matrix feeding circuit. The design method of the subarray and an evaluation of its characteristics in the 19 GHz band are discussed.