A single semicircle shape Complementary Split Ring Resonator (CSRR) is designed to enhance isolation by suppressing mutual coupling between MIMO antennas. Furthermore high level of mutual coupling by introducing circular slot in-between patch antennas on the substrate which creates additional coupling path between the patch antennas also opposes the some leakage signals coming back from the opposite coupling path after CSRR is etched from ground plane. The proposed patch antenna dimensions are chosen as 37.26 x 28.13 mm for operating at 2.51 GHz frequency, and the low-cost dielectric material, FR-4 (εr = 4.4), is chosen as the dielectric substrate with 1.6 mm height. The S parameters of proposed antenna prototype are characterized by using VNA. The measured return loss (S11) and isolation (S21) are -23.13 dB & -56.8 dB respectively. The results show that by introducing semicircle CSRR and circular slot, the structure provides a 33.2 dB improvement in mutual coupling for MIMO antenna. Hence, the proposed structure provides a better isolation between two antennas without affecting antenna performance.
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