Compact six-sector antenna using three intersecting dual-beam microstrip Yagi-Uda arrays with common director

This paper presents a novel compact planar six-sector antenna suitable for wireless terminals. Our new design yields low-profile and extremely compact multisector antennas because it allows microstrip Yagi-Uda array antennas to share director elements. Two microstrip Yagi-Uda array antennas are combined to form a unit linear array that has a feed element at each end: only one of them is excited at any one time and the other is terminated. A numerical analysis shows that applying a resistive load to the feed port of the terminated element is effective in improving the front-to-back ratio. We investigated the radiation pattern of a six-sector antenna, which uses three intersecting unit linear arrays, and identified the optimum termination condition. From the results of measurements at 5 GHz, we verified the basic properties of our antenna. It achieved high gain of at least 10 dBi, even though undesired radiation was suppressed. A rudiution puttern suitable for a six-sector antenna could be obtained even with & substrate having a diameter of 1.83 wavelengths, i.e., an area 75% smaller than that of an ordinary antenna with six individual single-beam microstrip Yagi-Uda arrays in & radial configuration. We also fabricated an antenna for the 25-GHz band and found that it has potential for high antenna performance, such as antenna gain of over 10 dBi even in the quasi-millimeter bond.