ABSTRACT This letter presents a compact wideband four‐port multiple‐input multiple‐output (MIMO) antenna designed for ISM band and wireless communication applications. The primary design challenges addressed include achieving wide impedance bandwidth, maintaining high inter‐element isolation, and ensuring compactness within a limited substrate area. To mitigate mutual coupling, four meander‐line monopole radiators are arranged in an orthogonal configuration, while a circular ring integrated with symmetric stubs is employed to enhance impedance matching and decoupling. Additional ground stubs and defected ground structures are introduced to further suppress surface current coupling. The proposed antenna operates over a wide frequency range from 2.37 to 5.27 GHz and occupies a compact footprint of , where corresponds to the free‐space wavelength at 2.47 GHz. Fabricated on an FR4 substrate, the antenna is experimentally validated in an anechoic chamber. Measured results demonstrate isolation better than dB across the operating band. Key MIMO performance metrics indicate excellent diversity behavior, with an envelope correlation coefficient (ECC) of 0.038, diversity gain (DG) of 9.998, channel capacity loss (CCL) below 0.27 bits/s/Hz, and mean effective gain (MEG) below dB. The close agreement between simulated and measured results confirms the suitability of the proposed antenna for compact MIMO‐based wireless systems.
Maddirala et al. (Mon,) studied this question.