Least-Squares Equalizer Demonstrations Using a Full-Digital Bandwidth Sub-Nyquist-Sampled Wideband Beamformer on an RFSoC

Abstract

The radio frequency system-on-a-chip (RFSoC) has recently become a viable candidate for completely replacing traditional analog and digital front ends, facilitating the development of wideband phased-array systems where the modern-day RFSoC takes the comprehensive, dominate role in the architecture of the array. Wideband phased-array systems require high-fidelity compensation techniques capable of correcting imbalanced and dispersive channel effects for effective beamforming. This article provides solutions to these challenges by designing a wideband equalizer for a sub-Nyquist-sampled 1.6-GHz <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -band phased-array system implemented on a Xilinx 8-channel RFSoC, whose analog-to-digital converters (ADC) operate at 4 gigasamples per second. In brief, an RFSoC is a unique, state-of-the-art, highly integrated device that incorporates a field programmable gate array, high-speed ADCs and digital-to-analog converters with a system-on-a-chip architecture on a single monolithic device. By definition, true time delay beamsteering can be implemented digitally via a combination of integer-sample delays and fractional-sample delay finite impulse response filters. By modifying the filter structure of the fractional-sample delay filter bank to support complex coefficients, channel equalization is integrated with fractional-sample delay filters to mitigate undesired channel effects. For the first time, to the best of our knowledge, this article has developed an equalizer design methodology for an uncalibrated 8-element RFSoC-based sub-Nyquist-sampled wideband beamformer. Lab measurements confirm efficacy.