| Summary: | The WiFi 6E extends the WiFi 6 operation in the 6 GHz band and features the <inline-formula> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> MIMO system. Recently, many countries have also made the lower 6 GHz band (5.925-6.425 GHz) available for the license-exempt wireless local area network, including the WiFi 6E. For such MIMO systems featuring 8 spatial streams in the lower 6 GHz band, we propose the compact <inline-formula> <tex-math notation="LaTeX">$2\times2$ </tex-math></inline-formula> dual-polarized patch (DPP) antenna array with 8 isolated ports in a small size of 40 mm <inline-formula> <tex-math notation="LaTeX">$\times40$ </tex-math></inline-formula> mm (about <inline-formula> <tex-math notation="LaTeX">$0.66\lambda ^{2}$ </tex-math></inline-formula> at 5.9 GHz) to transmit 8 uncorrelated waves for the WiFi-6E MIMO access point featuring 8 spatial streams. In addition, over the operating band, the isolation of any two ports thereof is larger than 20 dB and the maximum port isolation is larger than 30 dB. The high port isolation of the compact <inline-formula> <tex-math notation="LaTeX">$2\times2$ </tex-math></inline-formula> DPP antenna array is owing to each DPP antenna therein clad with an L-shape metal wall. We also test the fabricated compact DPP antenna array and its application in the <inline-formula> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> MIMO system in an on-campus public indoor space. The measured <inline-formula> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> MIMO system capacity reaches about 53 bps/Hz, even though the tested public indoor space is not an ideally rich multipath environment. The obtained results imply that for the maximum 160 MHz channel in the WiFi-6E, the system capacity based on using the compact DPP antenna array in the practical public indoor space can be about 8.48 Gbps (53 bps/Hz <inline-formula> <tex-math notation="LaTeX">$\times160$ </tex-math></inline-formula> MHz), which reaches 88% of the WiFi-6E’s ideal projected system capacity of 9.6 Gbps. We present in this study the proposed compact DPP antenna array and its measured <inline-formula> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> MIMO system results.
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