CARMA Correlator: Reconfiguration and Signal Processing

CARMA (Combined Array for Research in Millimeter-wave Astronomy) is equipped with a flexible digital correlator, each band independently configurable by the observer in terms of center frequency and total bandwidth. The digital hardware contains Field-Programmable Gate Arrays (FPGAs) implementing digital filtering and decimation to provide a spectral bandwidth per band ranging from 2 MHz to 500 MHz. The first three correlator bands, which attained first-light in September 2005, utilize hardware from the Caltech Owens Valley Broadband Reconfigurable Array (COBRA) correlator reprogrammed to support CARMA spectral line operation. Upgraded hardware with enhanced functionality is currently in development. We discuss the capabilities of the correlator, the programming and design techniques used to achieve them, and directions for the future.