A compact 4-element printed planar MIMO antenna system with isolation enhancement for ISM band operation

Abstract

In this research, a small 4×4 printed Multiple-Input/Multiple-Output (MIMO) antenna for use in Industrial, Scientific, and Medical (ISM) systems with medical applications is presented. The proposed structure consists of four dragonflyshaped radiators and four stepped-ground planes. In this design, adjacent elements are placed perpendicular to each other to create the necessary isolation between them. Also, a novel decoupling-element is utilized between the radiatingelements as an innovation for enhancing the isolation. A pair of rectangularshaped slits on either side of the dragonfly-shaped radiation patch is employed for determining the frequency band of the antennas. Laboratory results show that the proposed MIMO antenna can cover the frequency band of 2.16 GHz to 3.2 GHz with isolation above 21.4 dB. Small dimensions of 0.63λ × 0.63λ mm2 and presentation of diversity performance with an Envelope Correlation Coefficient (ECC) of less than 0.001 for aligned elements and 0.00043 for orthogonal elements are other particular advantages of the proposed antenna. Keywords: MIMO antennas, ISM band, Monopole antenna, Medical application of antennas.