Mutual coupling reduction for monopole MIMO antenna using l-shaped stubs, defective ground and chip resistors

In this paper, a symmetrical and compact monopole multiple input multiple output (MIMO) antenna is designed with two feeding ports. To reduce the mutual coupling between antenna elements, the l-shaped stubs and the defective ground structure (DGS) are used, and additionally the chip resistors are loaded. By optimizing the length of stub, the elements isolation can be improved remarkably. Then, two rectangular slots are etched on the metal ground as DGS to change the path of electric current so as to enhance the isolation further. Also, through loading the chip resistors to control the coupling current on the stubs, the isolation can be strengthened once more. The simulation and measurement results show that this antenna has the mutual coupling of −36 dB, the envelope correlation coefficient (ECC) of 0.002 and the diversity gain (DG) of 9.99 dB at resonance along with the radiant peak gain of 4.03 dBi.