Compact four port slot based MIMO antenna with isolation enhancement

This paper presents the design of a compact arc shape slot antenna and its application in multiple inputs and multiple-output (MIMO) communications. The unit cell antenna has a footprint of 15 x 15 mm(2). The antenna with arc shape stub loaded feedline provides broadband impedance matching extending from 3 GHz- 9.5 GHz. The antenna is made dual-polarised using orthogonal feed structure. A four-port, two-element MIMO antenna is constructed by replicating the unit cell design in a parallel fashion. Broadband isolation enhancement is achieved by using a modulated microstrip line embedded with circular patches of varying diameters. The four-port MIMO antenna provides 10 dB additional enhancement in comparison with the unmodulated microstrip line decoupling unit cell. The prototype antenna is fabricated and the simulation results are verified using experimental measurements. The antenna offers an average peak gain of 5.2 dBi and efficiency greater than 75%. The MIMO parameters such as envelope correlation coefficient, diversity gain, mean effective gain are evaluated and presented. The proposed antenna is one of the most compact 4 port solution reported in the literature.