Authors: Muhammad Umar Khan
Source: FERMAT, Volume 35, Communication 10, Sep.-Oct., 2019
Abstract: Multiple-input multiple-output (MIMO) systems promise high channel capacity and better reliability of communication. They are an important unlying technology in the current 4G/LTE to achieve higher data rates and will remain an enabling technology for the future 5G systems. Antenna is an important component of MIMO systems whose design requires special consideration as it can greatly affect the overall performance of the MIMO system. This talk will first briefly discuss the current approaches to design MIMO antennas that has been the focus in literature lately. The performance parameters to characterize MIMO antenna will be discussed. It will then focus on a new technique to design MIMO antennas with better performance in terms of correlation coefficient. Unlike the conventional approach where port isolation is increased to reduce correlation coefficient, the proposed approach adopts decorrelation of the radiation patterns of individual elements. Two approaches to design practical antennas based on field decorrelation will be presented. In the first technique, the MIMO antenna is designed in a low profile Fabry-Perot (FP) cavity configuration. A phase-gradient partially reflective surface (PRS) is used as a superstrate above the antenna elements which forms the FP cavity and tilt its beams to decorrelate the fields. The effectiveness of the method is demonstrated by designing several antennas with two and four antenna elements in different frequency bands. The technique results in more than 95% reduction in the correlation coefficient value, thus projecting better MIMO performance. The proposed technique can be easily used to design radome enclosed MIMO antennas. The second technique is again based on field decorrelation. However, a new approach to design an all-dielectric device based on transformation electromagnetics is used. The device when used with MIMO antenna tilt its beams to decorrelate the fields. The design approach and its effectiveness will be discussed. Lastly, the limitations of the presentation techniques and the potential of future work based on the current work will be discussed..
Index Terms: Multiple-input-Multiple-Output (MIMO) Antenna, Correlation Coefficient, Fabry-Perot Cavity Antenna, Partially Reflective Surfaces, Transformation Electromagnetics
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Field Decorrelated MIMO Antenna : A New Approach for MIMO Antenna Design