Collocated Electric and Magnetic Dipoles With Extremely Low Correlation as a Reference Antenna for Polarization Diversity MIMO Applications

In this letter, a magnetic dipole (M-dipole) and an electric dipole (E-dipole) are designed to form a collocated polarization-diversity-based dual-antenna system. The M-dipole is a modified shielded loop with multiple feed, and the E-dipole is a traditional λ/2 dipole. Measured results show that both radiators have ideal impedance matching and port isolation and identical omnidirectional pattern with perfect orthogonal polarization at 860 MHz. The upper bound of the envelope correlation coefficient ρ_emax, with the measured antenna efficiency taken into account, is only 0.018, and it is the lowest value when compared to some previous publications. Excellent effective diversity gain and channel capacity are also achieved at the operating frequency. The proposed dual-antenna system can mainly be used as a reference antenna for evaluating the performance of future collocated polarization-diversity-based multiple-input-multiple-output (MIMO) antennas.