Multidimensional (MD) Circuits and Systems for Emerging Applications Including Cognitive Radio, Radio Astronomy, Robot Vision and Imaging

Advances in the performance of VLSI circuits are leading to a number of emerging applications of multidimensional (MD) filters. Early progress was focused on the numerical design of two dimensional (2-D) transfer functions and the challenging stability issues associated with low-complexity infinite impulse response (IIR) implementations. However, over the last decade or so, important practical advances have occurred in the design of 3-D and 4-D IIR filters, leading to some important emerging applications. In this tutorial article, some of these applications are described, with emphasis on 2-D spatio-temporal beamforming and 4-D light field processing. In particular, advances in spatio-temporal beamforming for cognitive radio systems and for synthetic aperture radio telescopes are considered. In the 4-D case, we describe a class of 4-D light field filters for image processing, 4-D hyper-fan filters for low-light imaging, depth filtering, denoising and the attenuation of distracting objects, with applications in computational photography and habitat monitoring. Both analog and digital systolic VLSI circuit implementations are described with emphasis on recent progress using field programmable gate array (FPGA)-based and digital VLSI circuits that can potentially operate at radio frequencies in the multi-GHz range. These new innovations open up exciting possibilities for real-time MD filters having frames rates in the multi-GHz for emerging radio frequency (RF) antenna signal processing and imaging systems.