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This article presents a dual-band closed-slot multiple-input multiple-output (MIMO) antenna for terminal wireless applications. By simply inserting additional slots between the closely spaced parallel-arranged radiation slots, the signal impedances of common mode (CM) and differential mode (DM) can achieve similar status, and the strong mutual coupling effect is then eliminated. The proposed slot antenna pair shows good isolation of better than 20 dB across the desired Wi-Fi bands. In addition to the one-wavelength slot antenna, flexible extension to a more compact half-wavelength slot pair is given for future industrial design (ID), which provides further validation of the method. We fabricate the $4\times4$ MIMO antenna system constituted by two sets of one-wavelength closed-slot pairs. The experimental results show that the proposed MIMO antenna can offer isolation of better than 18 dB, an envelope correlation coefficient (ECC) of lower than 0.1 between all ports, and a wide −3 dB efficiency bandwidths across the desired bands. The results confirm that the proposed antenna is a viable candidate for Wi-Fi communications inside routers. [ABSTRACT FROM AUTHOR]

This article proposes a novel design of the dual-band antenna pair. Starting from the single-band antenna pair composed of T-shaped monopole and T-shaped slot that are intersected with each other, orthogonal T-monopole and odd-symmetrical slot modes are excited. By adding symmetrical low-pass high-stop filters into the horizontal stub of the T-monopole and high-pass low-stop filters into the gap of the T-slot, an extra mode is introduced for each antenna, producing dual-band operation. Impedance bandwidths and radiation efficiencies of both bands can be adjusted flexibly using the filters. A detailed design guideline is given. The dual-band antenna pair operating at partial N78 (p-N78, 3.4~3.6 GHz) and partial N79 (p-N79, 4.8~4.9 GHz) is with a footprint of $15\times 6$ mm2. The measured results show that the average efficiencies are both −3.4 dB at p-N78/p-N79 for the odd-symmetrical slot and −2.8 dB/−3.7 dB at p-N78/p-N79 for the T-monopole, isolations are better than −16.8 dB at p-N78 and −11.8 dB at p-N79, and ECCs are lower than 0.1 at p-N78 and 0.2 at p-N79. The proposed dual-band antenna pair exhibits great potential to be applied in the fifth-generation (5G) multiple-input multiple-output (MIMO) terminal. [ABSTRACT FROM AUTHOR]