A four element, planar, compact UWB MIMO antenna with WLAN band rejection capabilities

A planar, compact UWB MIMO antenna with four elements that accomplish band rejection from 4.91 to 6.41 GHz is presented. Rejection is accomplished using an L-C stub connected to the ground plane. The length of the stub is changed to reject the band starting from 2.5 GHz to above 8.8 GHz. The perpendicular placement of the elements enables polarization diversity and attains high isolation. Elements 3 and 4 are 180 degrees mirrored transforms of elements 1 and 2 on the opposite corners of the substrate. The antenna measures 50 x 50 mm(2) only with all four elements placed. The simulated results are validated by measurements of a fabricated prototype. The design attains the targeted specifications over the entire bandwidth of 2 to 12 GHz with a reflection coefficient better than -10 dB (except the rejected band), isolation more than 17 dB, low envelope correlation, low gain variation and strong rejection of the signals in the WLAN band. The small size and reduced complexity to obtain WLAN rejection makes the proposed design very useful for diversity applications and portable handheld devices with MIMO antennas as designed by panorama antenna.