A Four-Port MIMO Antenna Using Concentric Square-Ring Patches Loaded With CSRR for High Isolation

A novel four-port multiple-input-multiple-output (MIMO) antenna system is designed using concentric square-ring patch antennas. All four ports are made to resonate at 2.4 GHz ISM band with an overall system dimension of 60×60×1.6 mm
³
. This design uses complementary split-ring resonator (CSRR) loaded on its ground plane for enhanced isolation of - 22 dB between patch antenna elements. CSRR reduces mutual coupling by about 6.5 dB. The antenna operates with a 2:1 VSWR bandwidth of 75 MHz centered at 2.45 GHz. This collocated antenna system satisfies MIMO diversity performance with low envelope correlation between its waveforms. The effectiveness of concentric rings in MIMO design along with proposed isolation enhancement technique is validated using measurements from a prototype.