MIMO antenna performance with isolator

Abstract

In this article, the effect of an isolator in a multiple-input multiple-output (MIMO) antenna is analyzed in terms of its efficiency and isolation. An isolator is frequently utilized in MIMO antennas; however, the use of an isolator can aggravate the bandwidth or efficiency performance even though its isolation performance is improved. To develop a way of applying an isolator without sacrificing the bandwidth or efficiency performance, it is important to note that the characteristic modes excited by the MIMO antenna are related to the performance of the isolator. Two MIMO antenna systems using different ground characteristic modes are implemented to analyze the effect of the isolator. Via the isolator, both MIMO antennas achieved improved isolation, but the reference antenna underwent severe bandwidth degradation and efficiency degradation (from 31.81% to 16.69%), whereas the proposed antenna had relatively smaller reductions in bandwidth and efficiency (from 53.14% to 46.87%).