Collocated MIMO travelling wave SIW slot array antennas for millimetre waves

A novel four-element collocated travelling wave substrate integrated waveguide (SIW) multiple-input multiple-output (MIMO) antenna covering millimetre wave (mm-wave) bands (28–32 GHz) is presented. The antenna exhibits a matching bandwidth of more than 4 GHz and a measured gain of 15 dBi. The MIMO antenna elements are collocated, thus significantly reducing the size of the proposed design. To spatially isolate the beams (obtain lower correlation coefficient) of the MIMO antenna elements, the beams are oriented in different directions. The slots within each SIW array are designed to provide tilted beams, thus eliminating the need for a beam switching network. Four distinct beams are formed towards ±10° and ±30°. The dimension of the four-element MIMO SIW design is 68 × 30.68 × 0.5 mm3. The proposed antenna has a high gain, compact size, simpler feeding and enhanced MIMO capability compared to other SIW antennas proposed in the literature.