“…Various hybrid methods exist, such as the use of EBG and DGS together [ 34 ], L-shaped stubs, defective ground, and chip resistors used together [ 35 ], the use of the DGS method on the ground plane and epsilon-and-mu-near-zero-based metasurface superstrate [ 36 ], and the use of slot and parasitic element structures [ 37 ]. Moreover, various techniques have been employed to enhance the isolation levels in MIMO antennas by mitigating mutual coupling effects, such as the decoupling network [ 38 ], the integration of vias [ 39 ], a zigzag-shaped slotted structure in the ground plane [ 40 ], a partially reflecting surface [ 41 ], a partial ground surface [ 42 ], a partial ground surface combined with metasurface [ 43 ], a slot in the ground plane [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ], decoupling branches [ 52 ], and a stub in the ground plane [ 53 ]. The techniques for enhancing isolation used in prior research are known to be expensive and involve several processing steps.…”