A 4-Port Diversity Antenna With High Isolation for Mobile Communications

A novel wideband four-port diversity antenna that is capable of exciting four different radiation patterns is presented. The antenna consists of four magnetoelectric dipoles arranged in a ring configuration above a ground plane and a vertical electric monopole at the center of the ground plane. A matching network is used to combine the signals from the four magnetoelectric dipoles to produce two orthogonal broadside modes and one conical mode with horizontal polarization. The electric monopole is used to generate a conical beam with vertical polarization in electric feed. The performance of the antenna is studied computationally. A prototype operated at around 2.4 GHz was constructed and tested. Experimentally, the antenna exhibits about 22.2% overlapped bandwidth of the four ports. The two orthogonal broadside modes have about 11 dBi average gain. Whereas for the two orthogonal conical modes, an average gain of 6 dBi is achieved. The measured radiation patterns of the four degenerate modes are stable within the operating band. The measured isolations between different ports are generally less than -26 dB within the overlapped bandwidth. The measured radiating efficiencies of the four modes are all over 80% within the operating band.