Circular Polarized MIMO Antenna with Plus shaped Defected Ground Structure for ISM range spectrum Application

This proposed work proposes an incredibly isolated circularly polarized (CP) multiple-input-multiple-output (MIMO) antenna designed for the 5.8 GHz Industrial, Scientific, and Medical (ISM) band. The antenna features four circular patch elements arranged orthogonally to ensure enhanced isolation and efficient performance. Circular polarization is achieved through precise microstrip patch geometry, while a plus-shaped defected ground structure (DGS) significantly improves isolation and axial ratio bandwidth (ARBW). The design leverages an FR-4 epoxy substrate with a permittivity of 4.3 and achieves outstanding performance metrics. At the resonance frequency, the axial ratio is as low as 0.44, and the reflection coefficient is better than -30.30 dB. Critical MIMO parameters include an extremely low envelope correlation coefficient (ECC) of ≤.000017, diversity gain (DG) of ≥ 10 dB, isolation exceeding −33.16 dB, and a total active reflection coefficient (TARC) below −35 dB. The channel capacity loss (CCL) is maintained under 0.04 bits/sec/Hz, and the mean effective gain (MEG) is approximately −3.01 dB to -3.7 dB throughout the functional band. These results highlight the proposed CP MIMO antenna’s suitability for ISM band applications, offering enhanced isolation, superior polarization performance, and reliable operation. The innovative use of DGS and orthogonal patch arrangement underscores the novelty and practical potential of this design.These accomplishments and results indicate the antenna more appealing for usage in ISM band applications.