Offset planar MIMO antenna for omnidirectional radiation patterns

Abstract

An offset quad element multi-band planar MIMO antenna with omnidirectional radiation patterns is proposed for nonline of site (NLOS) communication on low-cost FR-4 dielectric substrate for 4G and future technologies. A 1 × 2 power divider arm results in dual beam and enhances diversity parameters and omnidirectional radiation patterns. Moreover, the MIMO antenna limits the proximity/coupling effects using a T-shaped isolator and achieves more than 12.4 dB of isolation between the radiating ports. The proposed design covers WLAN/WiMAX bands with gain and radiation efficiency of more than 2.6 dBi and 71%, respectively, in 2:1 VSWR bands of bandwidths 16.39% (2.24-2.64 GHz) and 7.88% (3.41-3.69 GHz). The −10 dB impedance bandwidth is more than 280 MHz in each band. An ECC level of ≤ 0.01 has been achieved in the whole band.