Compact multiport antennas for high spectral efficiency

The pursuit of wireless spectral efficiency draws on many different research areas. The area of largest potential impact is the deployment of multiport antennas. This is because it is the only technology that allows simultaneous sharing of the spectrum between many users, including full duplex operation in some circumstances. The spectral efficiencies of current communications system designs are still a long way from their information-theoretic limits, and similarly, current multi-element antenna designs seem to fall short of compactness limits. This invited paper, in tutorial style, touches on how wireless has reached this point, and the need to address grand challenges in information theory, communications techniques, networking, antenna elements and arrays, and signal theory. These aspects converge to set the scene for a new generation of adaptive antenna technology. The motivation is from basic energy and communications considerations. The design of compact multiport antennas requires an extension of classical performance metrics and new approaches to measurement and evaluation. Tools such as physics-based statistical channel and circuit models are likely to play a future role in the design of large-scale multiport antennas.