In this paper, we introduce a four-port self-isolated UWB MIMO antenna for diversity applications. First, we have developed a basic radiating element of the proposed antenna in four stages of design, where patches of geometrically different shapes were added at each stage to arrive at the final radiator form. The antenna was designed on an FR-4 substrate with a compact size of 28 × 28 × 1.6 mm3. A tapered microstrip feeding was employed to enhance the antenna’s impedance matching. An orthogonal arrangement of the four radiators was adopted to mitigate the mutual coupling between them, avoiding the use of a separate isolation structure. A prototype was built and measured with a close agreement between the experimental and simulated results. The MIMO antenna performed well in the entire frequency spectrum of 3.1–10.6 GHz, with an isolation better than 20 dB. The measured envelope correlation coefficient (ECC) was less than 0.001, the diversity gain (DG) was greater than 0.99 dB, and the total active reflection coefficient (TARC) was less than −10 dB. The performance of the proposed antenna design was compared with existing designs. The comparison showed that the proposed quad-element UWB MIMO array is compact, has good isolation and diversity performance compared to existing designs, and is well-suited for wireless diversity applications.

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A compact, four-element planar MIMO (Multiple Input, Multiple Output) antenna that operates in an ultra-wideband is presented for diversity application. The orthogonal position of the unit cells replicates the single antenna thrice, thereby decreasing mutual coupling. A UWB MIMO antenna measuring 35 × 35 × 1.6 mm3 is built using a microstrip line (50 Ω impedance) on an FR4 substrate having a thickness of 1.6 mm. The ground plane and radiator of this antenna are adjusted in several ways to bring it within its operating constraints between the frequencies of 3.1 GHz and 10.6 GHz. This technique makes the antenna small and covers the entire ultra-wideband (UWB) frequency range. The NI USRP was used to test the proposed MIMO antenna to determine its real-time performance. Based on the computed results, we conclude that this proposed antenna has outstanding characteristics in terms of performance and is suitable for wireless ultra-wideband indoor communication and diversity utilization with a small size.