The purpose of this study is to investigate and comprehend the performance analysis of a compact planar multiband multiple-input-multiple-output (MIMO) antenna, accomplished as a part of the ECE 533: Advanced Antenna Design course at Washington State University, Vancouver during the Fall 2022 semester. This study has introduced two symmetrical radiating elements joined by a neutralizing line to nullify the reactive coupling that makes up the MIMO antenna's basic structure. The basic MIMO antenna occupies an overall three dimensions of 60x80x0.8mm³ volume on a FR4 substrate with relative permittivity e_r=4.40 and loss tangent of tanδ=0.02. Coplanar waveguide (CPW) transmission lines of 50Ω have been used to feed the MIMO antenna. Furthermore, the base plane of the basic MIMO antenna has four slits and two compact rectangles of 2x12mm² cut into it to compensate the mutual coupling. The slit width, neutralizing line, substrate material, and its thickness have all been tuned in the proposed techniques to analyze different antenna parameters. The operating frequency band has been set to 500MHz-3500MHz for all the four cases. By employing simulation results obtained from the ANSYS HFSS environment, the performance of the fundamental MIMO antenna is evaluated and assessed against the optimized models. The optimized versions of the conventional MIMO antenna design have been thoroughly discussed in separate case studies. From our software simulation analysis, we find that optimized geometric shapes of the compact planar MIMO antenna show significant improvement in the isolation parameter of |S₂₁|, from <= 14.9 dB to <= 18.44 dB, <= 20 dB and up to <=27.68 dB for ease of understanding, no servicing frequencies have been predetermined.