Limited size MIMO antenna systems and mutual coupling challenge

Abstract

The wireless communication high data rate is achievable by installing more than one antenna in receiver and transmitter terminals as MIMO antenna. In order to obtain the MIMO gain (Envelope Correlation Coefficient (ECC) ≤ 0.5), the antenna elements must be at least separated by a distance of 0.5λ (λ is the operating wavelength of 0.7~3.8 GHz which is the frequency range of most of the current wireless communication applications). This value is big relative to limited sizes devices. A practical MIMO antenna should have a low signal correlation between the antenna elements and good matching features for input impedance. Moreover, MIMO system performance can be improved by reducing mutual coupling between closely spaced antenna elements. Miniature high isolated MIMO antenna system has been presented in this chapter; also many MIMO antenna systems were analyzed and categorized based on the implemented isolation techniques. Furthermore several MIMO antenna evaluation methods have been discussed.