Gain-Enhanced Ka-Band MIMO Antennas Based on the SIW Corrugated Technique

A novel single-layer substrate integrated waveguide (SIW) corrugated technique, consisting of an SIW slot and two SIW grooves, is proposed in this letter, based on which two high-gain and low-mutual-coupling Ka-band multiple-input-multiple-output (MIMO) antennas are demonstrated. The mechanism of gain enhancement of basic element is elaborated first before the analyses of the MIMO antennas. The simulated and measured results show that the elements of MIMO 1 and 2 antennas have an average 1.6 GHz (5.8%) bandwidth from around 26.8 to 28.4 GHz, and the gains can be up to 9.5 and 11 dB, respectively, with approximately 3 and 4.5 dB gain enhancement compared to those without SIW grooves. More than 20 dB high isolations between the elements can be achieved for both MIMO antennas. Subsequently, the study of envelope correlation coefficients exhibits their good MIMO performance.