LAUSR

A novel and high-performance four-element ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is proposed in the paper. The proposed antenna is designed by using a novel integration technology of the symmetric layout, orthogonal structure, four-directional staircase-shaped decoupling, and multi-slit and multi-slot techniques. The mutual couplings among the antenna elements are significantly reduced by introducing the symmetric orthogonal and separated four-directional staircase-shaped structure. Furthermore, the antenna size is effectively miniaturized, and its impedance bandwidth is broadened by using a two-sided symmetric layout, partial and defected ground structure, the decoupling structure, and multi-slot and multi-slit techniques. Therefore, the antenna has the low-profile structure and a small dimension of 39mm $\times 39$ mm $\times 1.6$ mm. Moreover, the proposed antenna achieves triple band-notched characteristics by embedding different type slots and slits on the square radiating elements, default ground structure, and the decoupling structure, respectively. As a result, the antenna obtains the wider bandwidth of 2.30–13.75 GHz with the notched bands of 3.25–3.75 GHz, 5.08–5.90 GHz, and 7.06–7.95 GHz. The three notched bands are good in agreement with the existing interference bands of WiMAX (3.3–3.7 GHz), WLAN (5.15–5.875 GHz), and ${X}$ -band (7.1–7.9 GHz), respectively. In addition, the proposed antenna also has a lower mutual coupling (<−22dB), lower envelop correlation coefficient (ECC<0.02, except for the three notched bands), high multiplexing efficiency ( $\eta _{\mathrm {mux}}> -3.0$ dB), stable gain, and quasi-omnidirectional radiation patterns at the entire impedance bandwidth. Therefore, a good tradeoff of the performance is obtained for the proposed antenna. The proposed antenna can be a good candidate for UWB-MIMO wireless communication applications, and especially for portable UWB-MIMO systems.