(The) design of the MIMO antenna with high port isolation and performance evaluation in reverberation chamber

Abstract

Wireless communication devices require high data rate for various mobile services. Multiple-Input-Multiple-Output (MIMO) antenna which uses several antennas at both transmitter and receiver is one of the solutions for increasing spectral efficiency. One of the most noticeable techniques for the next generation (4G) wireless communication is Long-Term-Evolution (LTE). MIMO antenna is essential for this technique. However, design of the MIMO antenna which has the limited space is an enormous challenge at low frequency. Strong coupling between antenna elements in mobile handset is caused due to share of the small ground plane. This leads to degradation of the diversity/MIMO antenna. Thus, we have to decouple antenna elements of diversity/MIMO system. Recently, various methods have been found to improve isolation between the antenna elements [1]-[6]. Among those methods, decoupling technique composed of two transmission lines and a shunt lumped element has the advantages of design and application [6]. However, if the reflection coefficients (S11, S22) of the dual antenna system are not negligible quantities, established decoupling technique do not properly work. Thus, the reflection coefficients should be considered when applying decoupling technique to this case for accurate design of the decoupling network. Performance evaluation of the diversity/MIMO antenna made by this technique should be achieved to validate the effect of the decoupling technique. But anechoic chambers do not have ability to evaluate the performance of the diversity/MIMO antenna. Moreover, it is extremely expensive and occupies large space. Measuring radiation efficiency in anechoic chambers is available, but time consuming. Since the end of the 1990s, reverberation chamber (RC) has been used to characterize diversity/MIMO antennas. Originally, the RC has been used for EMC testing in the last 30 years. Since, these days, mobile and wireless applications are used in fading environment d...