12-Element SIW MIMO Antenna With an Integrated Self-Triplexing System for Advanced Wireless Services

This article introduces a novel 12-element MIMO antenna with an integrated self-triplexing system using a substrate-integrated waveguide for advanced wireless communication services. This antenna comprises 12-stepped shaped radiators within a SIW square cavity, each with an individual 50 inset-fed line to excite its corresponding radiator. 12-radiators are arranged into three groups with different radiator sizes to achieve self-triplexing operation. Each group contains four identical radiating elements to function as a MIMO antenna system. The proposed integrated MIMO antenna triplexer operates at three distinct frequencies: 4.49 GHz, 6 GHz, and 6.72 GHz, respectively. The antenna is fabricated on a single-layer substrate to validate its performance. The mutual coupling among any radiator is maintained at less than -22.5 dB within the -10 dB impedance bandwidth (IBW). The gain of the proposed antenna is 4.11 dBi, 4.93 dBi, and 6.20 dBi at the respective frequencies. The proposed antenna has an envelope correlation coefficient (ECC) of less than 0.03 at 4.49 GHz, 0.002 at 6 GHz, and 6.72 GHz, with a diversity gain of more than 9.99 dB across all bands. This antenna eliminates the need for additional signal-separation circuits in multi-band MIMO systems due to its inherent band-separation capability.