Current issues and challenges of MIMO antenna designs

The demand for high data rate and channel bandwidth is always the primary area of concern in modern wireless communication systems. All the modern wireless communication system applications are rapidly shifting towards multiple input multiple output (MIMO) from single input and single output (SISO) and single input multiple output (SIMO) systems, increasing the demand for the integration of multiple antennas in the users equipment. The development of MIMO antennas and its performance evaluation for the portable wireless communication terminals have attracted many researchers to improve channel capacity, bandwidth, gain, polarization diversity and reduce coupling between inter elements. Further these systems also demands that the multiple element antenna (MEA) should be minimized so that they can fit in the compact and robust user equipment, and support multiband operation for the equipment reusability in the different regions of the world. Antenna designers have ample vacuum in the development of novel antenna systems for the new generation networks by enhancing the impedance bandwidth and multiband resonance. In addition improving radiation pattern diversity reduces the correlation coefficient and increases MIMO antenna performance. This review paper is focused on the related work in the field of MIMO antenna designs. Researchers have proposed various different techniques to design antennas at a range of microwave bands of interest, where the key concern of the research is to enhance the channel capacity by reducing the correlation coefficient and increasing the isolation between multi element antennas.