Design of Compact 4 x 4 UWB-MIMO Antenna with WLAN Band Rejection

A compact 4 x 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm x 60 mm), printed on a FR4_ epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than -10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36-6.34GHz while the values of all isolation coefficients are below -15 dB and the correlation coefficient of MIMO antenna is less than -28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context.