In this paper a dual-polarized multiple-input multiple-output (MIMO) antenna system for fifth-generation (5G) indoor base station applications resonating at 3.5 GHz has been proposed. The initial design is a conventional patch antenna, and characteristic mode analysis (CMA) is used to determine its dual-polarized characteristics. Both orthogonal modes are excited using the full-wave approach with a 50 Ohm dual-port coaxial feed line, and operated at 3.5 GHz. The non-contact feed method is used to improve isolation between ports. Inserting an air gap between the antenna substrate and the ground metal sheet improves gain and bandwidth. Further 2x2 MIMO antenna with 8-port is designed on low cost FR4 dielectric material with 120*120*5.17 mm3 compact volume. The MIMO antenna’s performance are examined by simulation and experimental. For the proposed MIMO, high isolation, high efficiency, and appropriate gain-level characteristics have been obtained. Furthermore, throughout the whole band of interest, the calculated total active reflection coefficient (TARC) and envelope correlation coefficient (ECC) of the antenna components are very low, indicating that the proposed multi-antenna systems are capable of enormous MIMO and diversity applications. Furthermore, the antenna avoids the use of complex feeding mechanisms such as baluns or directional couplers.