Compact Two Elements MIMO Antenna: Isolation and Gain Enhancement by Using FSS for Ultra-wideband Applications

This work presents a two-element compact multiple-input multiple-output (MIMO) antenna for ultra wideband (UWB) applications. The antenna is fabricated on FR4 substrate with compact size of 20 × 28 ×1.6 mm ³ (0.26λ ₀ ×0.37λ ₀ ×0.022λ ₀ , where λ ₀ the free space wavelength at 4.2 GHz). Two tree-shaped radiators are used for implementing the MIMO antenna. The modified ground structure is used between two antennas to enhance the isolation. A pair of additional rectangular ground stubs are employed to further enhance the isolation and the impedance bandwidth as well. The gain and isolation of the MIMO antenna are further enhanced by incorporating a polarization insensitive angularly stable frequency selective surface (FSS) structure. The proposed model acquires an impedance bandwidth of 3.6 – 10.6 GHz with the accomplishment of isolation more than 20 dB and peak gain of 9.85 dBi. The MIMO ability of the antenna integrated with FSS is demonstrated in terms of standard envelop correlation coefficient (ECC), diversity gain (DG), TARC and time domain analysis. The measured ECC and DG are <0.005 and > 9.87dBi with the phase response executing the linear variation. All the characteristics values confirm that the proposed MIMO antenna is fit to be implemented as a good candidate for UWB applications.