Frequency-Multiplexed Array Digitization for MIMO Receivers: 4-Antennas/ADC at 28 GHz on Xilinx ZCU-1285 RF SoC

Najath Akram, Arjuna Madanayake, Sravan Pulipati, Viduneth Ariyarathna, Satheesh Bojja Venkatakrishnan, Dimitra Psychogiou, John Volakis, Theodore S. Rappaport, Thomas L. Marzetta
<span title="">2021</span> <i title="Institute of Electrical and Electronics Engineers (IEEE)"> <a target="_blank" rel="noopener" href="https://fatcat.wiki/container/q7qi7j4ckfac7ehf3mjbso4hne" style="color: black;">IEEE Access</a> </i> &nbsp;
Communications at mm-wave frequencies and above rely heavily on beamforming antenna arrays. Typically, hundreds, if not thousands, of independent antenna channels are used to achieve high SNR for throughput and increased capacity. Using a dedicated ADC per antenna receiver is preferable but it's not practical for very large arrays due to unreasonable cost and complexity. Frequency division multiplexing (FDM) is a well-known technique for combining multiple signals into a single wideband
more &raquo; ... In a first of its kind measurements, this paper explores FDM for combining multiple antenna outputs at IF into a single wideband signal that can be sampled and digitized using a high-speed wideband ADC. The sampled signals are sub-band filtered and digitally down-converted to obtain individual antenna channels. A prototype receiver was realized with a uniform linear array consisting of 4 elements with 250 MHz bandwidth per channel at 28 GHz carrier frequency. Each of the receiver chains were frequency-multiplexed at an intermediate frequency of 1 GHz to avoid the requirement for multiple, precise local oscillators (LOs). Combined narrowband receiver outputs were sampled using a single ADC with digital front-end operating on a Xilinx ZCU-1285 RF SoC FPGA to synthesize 4 digital beams. The approach allows M -fold increase in spatial degrees of freedom per ADC, for temporal oversampling by a factor of M . INDEX TERMS Analog-digital conversion, antenna arrays, MIMO systems, millimeter wave radio communication. 142744 VOLUME 9, 2021 NAJATH AKRAM (Member, IEEE) received the B.Sc. degree in electrical and information engineering from the University of Ruhuna, Sri Lanka, in 2016, and the Ph.D. degree in electrical and computer engineering from Florida International University, in 2020, with a focus on digital and mixed domain hardware complexity reduction algorithms and implementations for massive MIMO. His research interests include multi-dimensional signal processing, RF systems design, and antenna array processing.
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