In this paper, a co-located tri-polarized loop (TPL) antenna is proposed and a co-located tri-polarized dipole (TPD) antenna is also designed for multiple-input multiple-output (MIMO) performance comparison. Both antennas have satisfactory performances of impedance bandwidth and isolation. The channel measurements are conducted in a non-lossy reverberation chamber (RC), a lossy RC, a corridor and an office room. For both antennas, the measured average correlation coefficients (CCs) in the non-lossy RC are the smallest, close to 0.1, in the lossy RC are the largest, 0.3-0.5, and in the two indoor scenarios are slightly larger than that in the non-lossy RC. Except for the signal correlation, the relative path loss (RPL) should also be included to fairly compare the channel capacities. If the RPL is considered, a strong dependence of the channel capacity on the propagation properties can be seen. For both antennas, the channel capacities in the two indoor scenarios are 20%-30% smaller than that in the non-lossy RC. Interestingly, both antennas have similar condition numbers (CNs) in all the four scenarios, whose PDFs are close to that of the independent identically distributed (i.i.d) complex Gaussian channel, which reveals that both antennas can obtain nearly three independent parallel subchannels and good multiplexing performance.Index Terms-Tri-polarized loop (TPL), tri-polarized dipole (TPD), multiple-input multiple-output (MIMO), measurement.
0018-926X (c)
Abstract-The 2 × 2 multiple-input-multiple-output (MIMO) capacities of three types of colocated dual-polarized loop (DPL) antennas with different current distributions and isolations are investigated in the free space (FS) channel, the corridor with perfect electric conductor walls (PEC corridor) and the corridor with concrete walls (CON corridor), separately. Capacity results show strong dependences on both the structure and the position of the DPL antenna, in addition to the propagation conditions. For all the three propagation scenarios, the largest capacity can be reached is in the PEC corridor, employing the DPL antenna with a uniform current distribution and a high isolation. Specifically, for a 20 dB signal-to-noise ratio (SNR), the maximum dual-polarized MIMO capacity is 13.1 bps/Hz, which is 1.97 time of that obtained by the one-polarized loop. It is also noted that, the rich-multipath environment can increase the robustness of the DPL MIMO system and the difference of the MIMO capacity obtained by different antenna structures will get smaller with respect to that in the FS channel.
The channel matrix of a MIMO (multiple-input multiple-output) system composed of a virtual colocated tripolarized loop (TPL) antenna is measured in an anechoic chamber and an office room. Results show that in both scenarios, the TPL antenna can obtain a nearly 3 fold capacity increase over the one-polarized loop (OPL) antenna, and can obtain a nearly 1.5 fold capacity increase over the dual-polarized loop (DPL) antenna. Furthermore, in both scenarios, using the TPL antenna can obtain 3 nonzero eigenvalues, which indicates that three effective parallel channels can be generated. Numerical computations are also conducted by commercial software Ansoft HFSS, the simulated capacity results agree basically with the measured results.
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