Compact 4-Port MIMO Antenna-Diplexer Utilizing Slotted-HMSIW Technology

A new design for a 4-port multiple input multiple output (MIMO) self-diplexing antenna is introduced, utilizing half-mode substrate integrated waveguide (SIW) technology. This antenna operates simultaneously at 4.9 GHz for WLAN and 5.8 GHz for ISM band communications, maintaining an isolation of approximately 30 dB. By employing the half-mode topology, the antenna size is reduced by 50% while preserving the dominant mode TE110 characteristics. To enhance bandwidth, a rectangular slot is etched at the centre of each cavity, splitting the dominant mode into odd-TE110 and even-TE110 modes. Through careful optimization of antenna parameters and the perpendicular placement of radiating elements for different frequencies, the design ensures self-diplexing property. To validate the design, a prototype of the antenna is manufactured, and experimental results are verified with simulations. The proposed antenna demonstrates a peak gain of 5.2 dBi in the lower-frequency band and 5.9 dBi in the upper-frequency band, with a high efficiency exceeding 94% in both of the frequency bands. Additionally, all MIMO-diversity parameters were found to be within satisfactory limits.