Periodic Octagon Split Ring Slot Defected Ground Structure for MIMO Microstrip Antenna

In this work, a periodic octagon split ring slot defected ground structure for MIMO (Multiple Input Multiple Output) microstrip antenna is proposed. The prototype of MIMO microstrip antenna consists of four similar rectangular microstrip antenna elements with a partition of λ/4 distance. The antennas are printed on a 1.6mm thick FR-4 substrate with an overall dimension of 62.8 X 60 mm2. To improve the antenna parameters, the proposed MIMO microstrip antenna elements are etched with narrow rectangular edge slit and ground plane defected with periodic octagon split ring slot defected ground structure (POSRSDGS). The proposed MIMO microstrip antenna resonates at dual frequency points, i.e., 4.1GHz, 5.9GHz with a bandwidth of 88MHz and 454MHz along with minimum return loss of −22.7dB and −19.02dB, respectively. The envelope correlation coefficient (ECC) is lower than the acceptable limit across the dual operating bands. Mutual coupling coefficient (MCC) at dual resonating frequency points are −36.21dB and −42.93dB, respectively. The simulated and fabricated results are found in good agreement and ideal for wireless communication applications.