A variable tilted fan beam antenna for indoor base stations

In business cordless telephone and wireless LAN systems, a base station antenna is installed indoors. Conventional dipole or sleeve antennas are commonly used as the base station antennas. These antennas have the maximum radiation in a direction normal to the antenna axis. Accordingly, when the antennas are installed in an upper area of the wall or near the ceiling vertically, as is usually the case, the radio waves radiated toward most mobile terminals are off the maximum radiation angle. Furthermore, the antennas have an omnidirectional radiation pattern, and thus offer equal field intensities in all directions both toward the wall and into the room. Therefore, it is desirable for the base station antenna to have a beam tilted downward with a fan beam pattern on the horizontal plane. This paper proposes a new structural antenna to satisfy those requirements. Arranging two skew and off-center parasitic elements around a sleeve antenna, the antenna provides a variable downward beam tilt capability up to 22/spl deg/ while maintaining a uniform fan beam radiation pattern over 180/spl deg/ coverage.<>