Compact Pattern-Reconfigurable Monopole Antenna Using Parasitic Strips

A monopole antenna array with pairs of switchable parasitic strips is proposed to realize eight beams for azimuth omnidirectional coverage. The proposed antenna consists of one active monopole and four pairs of parasitic elements. Each pair of parasitic elements is formed by two switchable parasitic strips. By switching p-i-n diodes, a pair of parasitic strips can be used as a director or a reflector. By introducing a shorter parasitic strip between the monopole and the longer strip, the radiation impedance of the monopole is increased when the monopole and the reflector/director are closely positioned. As a result, the diameter of the whole antenna array is only 0.1λ0, where λ0is the operating wavelength in free space. For demonstration, the antenna is designed to realize eight beams in the azimuth plane with a 45°-angle interval at 1.575 GHz for global positioning service with the peak gain of all the beams larger than 7 dBi at the elevation angle of 60°.