KEYNOTE: A MIMO Perspective of Phased Arrays and its Applications

Phased arrays are most often thought of as just a way to electronically focus, steer, direct and receive energy. In this traditional modality, all the antenna elements work cooperatively to illuminate and observe radar targets or to transmit and receive communications signals in a directed way. It turns out that multiple-in multiple-out (MIMO) systems have many degrees of freedom that can be explored to implement a variety of imaging, spatial spectrum analysis and energy steering systems, not to mention other radar and data transmission modalities. It helps to view beamforming as an analogy to discrete time Fourier Transforms and to the sampling process of analog to digital converters. Once in a matrix format, the number of degrees of freedom in forming beams, nulls or multi-path combining becomes clearer. This formulation can be extended to represent focal plane arrays and reflective surfaces. Arrays also complement synthetic aperture radars and imagers to increase resolution for the same aperture. Extracting more value from phased arrays requires RF, analog, digital signal processing and high-performance compute to be jointly optimized according to the application.