Implementation and MIMO Performance Assessment of Two Quad-Polarized Antennas

In this letter, two compact, colocated, low-coupled, quad-polarized (QP) antennas are proposed based on two dual-mode radiation bodies to achieve compactness and high isolation. The first antenna obtains four polarizations by orthogonally placing two dual-mode loops; the second antenna includes a dual-mode loop and a miniaturized dual-polarized patch based on fractal structures inside the loop. To investigate the performance of QP multiple-input–multiple-output (MIMO) systems, channel parameters including correlation coefficients, degree of power balance, and channel capacities are analyzed based on the measured data. Results show that, high channel capacities can be achieved both in a realistic office room and a rich scattered reverberation chamber, which are very close to that of the 4 × 4 independently identically distributed (i.i.d.) Rayleigh channel. It is revealed that both correlation coefficient and degree of received power balance have strong influence on the performance of a MIMO system, which are related to the radiation properties of the antenna and the polarimetric characteristics of the propagation environment.