A novel multiple‐input–multiple‐output fractal antenna was proposed in this study. The proposed antenna consisted of two symmetrical radiating elements placed on opposite sides to achieve spatial diversity with a highly compact size (8 × 8 × 0.8 mm3). Each radiating element is configured by a process of three iterations, and an additional semi‐crescent structure scaled down in each iteration placed in a cascade arrangement. This arrangement generated circularly polarised radiation with an axial ratio bandwidth of (2.2–3.2) GHz, which was about 24% of the entire operational range of (0.1–4.3) GHz that can be used for many wireless communications such as long‐term evolution, radio‐frequency identification, wireless fidelity, and worldwide interoperability for microwave access applications. The envelope correlation coefficient, mutual coupling, circular polarisation (CP), and current distribution were studied and analysed to improve the design process. Compared to other related antennas, the proposed antenna can improve many radiation characteristics such as diversity (left‐hand CP) and (right‐hand CP), wide axial ratio bandwidth, and acceptable gain in a small antenna size.

To design a slot antenna intended to work at four bandwidth frequency groups, which meet the specifications of (DO,1xRTT-3G), (WiMAX-IEEE802.11e), (WiMAX-IEEE802.16m) and (Wi-Fi.802.11b,g, & n) communications. The slot in the proposed antenna taken the form of the character (Q) that was feed by step impedance micro strip line design open mouth ended. The surface current distribution at resonant frequencies and the effect of varying the dimensions of the parameters on impedance bandwidth had been studied carefully in this research to enhance the performance of resonant frequency.

In this study, an Amer fractal slot antenna is proposed as a multiple input, multiple output (MIMO) antenna with four ports. The antenna is excited by CPW (coplanar waveguide) to control the leakage of electromagnetic energy, which leads to a high match between the antenna and input impedance, thus achieving dual operating bands of 1.5-19.2 GHz and 25-37.2 GHz for port 1, dual operating bands of 1.4-19 GHz and 20-35.5 GHz for port 2, a wide operating band of 1.4-29 GHz for port 3, and dual operating bands of 1.6-21 GHz and 22-37 GHz for port 4. Therefore, the proposed antenna meets all the market needs of wireless communication technologies such as 3G, Long Term Evolution (LTE, 2.6 GHz /3.5 GHz), Wireless Local Area Network (WLAN, 2.4 GHz/5 GHz), Worldwide Interoperability for Microwave Access (WiMAX, 2.5 GHz/3.5 GHz/5 GHz), Industrial, Scientific and Medical (ISM, 2.4 GHz/ 5 GHz), and 5G (5-6 GHz and 27-28 GHz). The proposed antenna can be used as dual opposite ports for the frequency range 1.5-15 GHz and as four-element MIMO arrays for frequencies of 15-30 GHz. The MIMO fractal antenna has circular polarization characteristics with axial ratio bandwidths (ARBWs) of 4.7-5.8 GHz for port 1, 2.5-2.6 GHz and 5.4-6.5 GHz for the port 2, 4-5.9 GHz for port 3, and 5.5-10 GHz for port 4. Due to its compact size (33 mm × 33 mm × 0.8 mm), low profile, and acceptable values of gain and efficiency, the proposed antenna is suitable for many portable wireless communication devices.

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