Compact Design of a 4-Port MIMO Antenna-Diplexer Leveraging HMSIW Cavities

A novel 4-port MIMO self-diplexing antenna design is presented, utilizing half-mode substrate integrated waveguide (HMSIW) technology. This antenna operates at 4.9 GHz for WLAN and 5.8 GHz for ISM communications, achieving approximately 30 dB isolation. The half-mode topology reduces the antenna size by 50% while retaining the TE110 mode characteristics. To increase bandwidth, a rectangular slot is added in each cavity, splitting the mode into odd-TE110 and even-TE110. Careful optimization of antenna parameters and the perpendicular arrangement of radiating elements ensure effective self-diplexing. A prototype is manufactured, with experimental results confirming simulations. The antenna shows peak gains of 5.2 dBi at the lower frequency and 5.9 dBi at the upper frequency, with efficiencies exceeding 94% in both bands. All MIMO-diversity parameters also met satisfactory levels.