Enhanced isolation of MIMO cavity antenna using substrate integrated waveguide technology

In this paper, a cavity-backed semi-circular antenna with rectangular slot for MIMO (multiple-input multiple-output) systems is presented. The proposed MIMO antenna comprises two rectangular slots etched on the ground plane and excited by two microstrip transmission lines. The substrate integrated waveguide (SIW) is integrated to enhance the isolation between the two antenna elements. The obtained results show that the antenna operates around 5.8 GHz with an impedance bandwidth between 5.65 and 5.9 GHz, with S-11 <= -10 dB, which is suitable for WLAN (wireless local area networking) applications. The fractional bandwidth of the reference MIMO antenna is 4.13%, while for the SIW MIMO case attains 4.31%. Moreover, the integration of SIW resonators leads to an enhancement of the isolation from 17.7 dB (reference antenna) to 30 dB. The achieved gain is about 5.6 dBi at the resonance frequency 5.8 GHz. The envelope correlation coefficient (ECC) is lower than 7 x 10(-5) across the operating bandwidth. The simulated results are in good agreement with the experimental ones. The fabricated antenna exhibits very acceptable radiation performances compared to the conventional one.