Two novel colocated dual-polarized antennas with extremely low mutual coupling for polarization diversity MIMO applications

This paper presents two novel colocated cross-polarized multiple-input-multiple-output (MIMO) antennas. One consists of two modified printed loop (MM) antennas with ideal impedance matching and port isolation, which can provide a wide bandwidth of 750 MHz. The simulated isolation between the two loops was -30 dB or less within 2.25-3.0 GHz. The other one is composed of an electric dipole and a magnetic dipole (EM), and ideal port isolation (better than -60 dB) is achieved within the entire band of 1.5-3.5 GHz. Computation results show that in the free space channel, a nearly twofold capacity gain can be obtained over the one-polarized single-input-single-output (SISO) system for both of the two dual-polarized antennas. The capacity gain obtained by the MM antennas is 1.975 and by the EM antennas its 1.995, for the communication distance larger than 0.1 m. In the ground reflected channel, the maximum capacity gain close to 2 can also be obtained for both of the two dual-polarized MIMO antennas, however, the capacity gains fluctuate with the communication distance. We get the conclusion that the characteristics of the multipolarized MIMO system is not only influenced by the antenna properties, but also influenced strongly by the propagation characteristics of the channel.