Abstract
In this paper, a novel super-wideband multiple-input multiple-output (SWB-MIMO) antenna system with high isolation has been proposed, each antenna element consisting of a spade-shaped radiation patch, a defected ground structure (DGS) as well as a windmill-shaped decoupling structure. The elliptical slot etched on the radiation patch and the rectangular DGS are jointly utilized to make better the radiation performance and impedance bandwidth. Both of four-element and eight-element SWB-MIMO antenna systems are simulated and analyzed, respectively. A prototype of the four-element SWB-MIMO antenna system with total dimensions of 58 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times58$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 1$ </tex-math></inline-formula> mm was fabricated to verify the concept of design using an FR4 material substrate. Measurement and simulation results indicate that the proposed SWB-MIMO antenna system can work in the frequency band ranging from 2.9 to 40 GHz with a mutual coupling of lower than–17 dB. Also, excellent performance has been achieved with a low envelop correlation coefficient (ECC) of lower than 0.04, high multiplexing efficiency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta _{\mathrm {mux}}$ </tex-math></inline-formula> ) of more than–3.0 dB, stable gain of up to 13.5 dBi as well as quasi-omnidirectional radiation properties. This design provides an important guideline for obtaining a super-wide MIMO antenna.
Highlights
With the rapid development of the high-frequency and microwave communication technology such as the fifthgeneration (5G) wireless networks and the internet of things (IoT), the need for high channel capacity and reliability is dramatically increasing for smart city, smart home wearable devices, and other applications
The four-element and eight-element SWB-Multiple-input multiple-output (MIMO) antenna systems are analyzed, respectively, and the results show excellent characteristics of SWB and high isolation
The results demonstrate that the isolations of eight-element SWB-MIMO antenna system perform well and are all lower than –19 dB, satisfying the requirements of MIMO antenna systems
Summary
With the rapid development of the high-frequency and microwave communication technology such as the fifthgeneration (5G) wireless networks and the internet of things (IoT), the need for high channel capacity and reliability is dramatically increasing for smart city, smart home wearable devices, and other applications. Since a multi-stepped impedance transformer exhibits wideband characteristics, it is a good candidate for achieving high isolation in UWB-MIMO antenna systems [14] As seen, this structure improves the coupling level between antenna elements in the high frequency band, and the isolation level achieves less than –15 dB in the whole frequency band.
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