Jonathan Weintroub (Center for Astrophysics | Harvard & Smithsonian) Co-Authors and affiliations are as listed in this Journal of Astronomical Instrumentation (JAI) paper https://www.worldscientific.com/doi/pdf/10.1142/S2251171716410063 <https://www.worldscientific.com/doi/pdf/10.1142/S2251171716410063> Topics: Lessons learned from recent digital correlator projects Emerging digital correlator concepts, technologies, and architectures SWARM: A 48 GHz Correlator and VLBI Beamformer for the Submillimeter Array The SMA Wideband Astronomical ROACH2 Machine (SWARM) is a 48 GHz bandwidth VLBI capable correlator and phased array deployed at the Smithsonian Astrophysical Observatory's Submillimeter Array (SMA) on Maunakea in Hawai’i. SWARM natively integrates two instruments: a correlator with 140 kHz spectral resolution across its full GHz band, used for connected interferometric observations, and a phased array summer, which is used when the SMA participates as a station in the Event Horizon Telescope (EHT) Very Long Baseline Interferometry (VLBI) array. For each SWARM quadrant, Reconfigurable Open Architecture Computing Hardware (ROACH2) units shared under open source from the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) are equipped with a pair of 5~gigasample-per-second Analog-to- Digital Converters (ADCs), a Field Programmable Gate Array (FPGA) processor, and eight 10 Gigabit Ethernet ports. A VLBI data recorder interface designated the SWARM Digital Back End, or SDBE, is implemented with a ninth ROACH2 per quadrant, feeding four Mark6 VLBI recorders with an aggregate recording rate of 64 Gbps. I will describe the design and implementation of SWARM, as well as its deployment at SMA, with reference to verification and science data. I will close with a few words about future technologies being considered for the SMA’s next generation of digital systems.