The paper provides an in-depth examination of the development & features of 5G spectrum allocations, along with MIMO antenna design. It gives an overview of massive MIMO technology & its uses to base station applications. The paper’s primary objective is to highlight the frequencies reserved for 5G and to demonstrate the impacts of MIMO designs. An array antenna for 5G applications has been developed, where we originally designed an array of rectangular patch antennas functioning as a Multi-Input-Multi-Output (MIMO) antenna operating at 28 GHz. This antenna is compact, measuring 14.89 mm × 42.90 mm. The antenna’s two-dimensional radiation patterns exhibit circularly polarized radiation pattern due to the array configuration. The proposed antenna is designed and simulated, the simulation result showing return loss of less than −10 dB with isolation, a gain of 6.7 dB at 28 GHz, and an 8.07 dB directivity at the operating frequency. This makes it a strong candidate for MIMO applications at 28 GHz band, allowing 5G cellular communications.