Design of Wideband Pattern Diversity Antenna for Mobile Communications

Abstract

A wideband four-port diversity antenna that is capable of exciting four different linear polarizations is presented. The antenna consists of four magneto-electric dipoles arranged in a ring configuration. These dipoles are supported by a cross-shaped feed over a modified ground plane. Three 180°hybirds are used to combine the signals from the four magneto-electric dipoles to produce two orthogonal broadside modes and one conical mode with horizontal polarization. A cross-shaped feed loaded below the four magneto-electric dipoles which are supported by four shorting-pins can radiate a conical beam with vertical polarization. The performance of the proposed antenna is studied numerically and experimentally. The prototype antenna is fabricated and tested successfully. It can achieve about 30% overlapped bandwidth with the centre frequency of 2.2GHz. The isolation between any two ports is greater than 17dB. The two orthogonal broadside modes exhibit about 10 dBi average gain. For the two orthogonal conical modes, an average gain of 6 dBi and 8dBi can be achieved. Measured radiation patterns of the four degenerate modes are stable within the operating band.