Some issues in the design of recent MIMO antenna systems

Multiple-input-multiple-output (MIMO) technology was introduced to overcome the saturated data rate capabilities of conventional single antenna systems given the limited bandwidth and power levels. For the past 10 years, MIMO solutions were provided for various wireless systems and it became a pillar in the fourth generation (4G) wireless standards and beyond. The proliferation of wireless devices in various applications and form factors made engineers and researchers propose numerous solutions for MIMO antenna systems. These multi-antenna systems need careful examination and design steps to be useful and provide the anticipated increase in data rates. Recently, it has been observed that several proposed MIMO designs suffer from some common fundamental issues that are highlighted and discussed in this work. The goal is to clarify and avoid them in the future.