A compact MIMO antenna has been designed explicitly for Ka-band for 5G wireless networks. The antenna uses four P-shaped radiating patches in E-shaped slots for polarization variety in the 20-40 GHz frequency band. The Rogers RT/duroid 5880 substrate (26 × 25 × 1.6) supports each patch and defective ground for each element. Polarization diversity lowers radiating element interference, making this antenna design advantageous. Therefore, the antenna has a wide bandwidth of 20 GHz. A high isolation level of over -20 dB has been attained by carefully examining the mutual connection between antenna radiators. After a detailed analysis of the radiation patterns, a gain of 17.6 dBi is found. Both total and radiating efficiency exceed 87% and 91%. MIMO system dependability is evaluated by assessing diversity characteristics including ECC, DG, CCL, MEG, and TARC, yielding findings of 0.0035, 9.98 dB, 0.013 bits/sec/Hz, -3 dB, and -10 dB. Simulations and observations show a significant agrement.