Design of an interim digital spectro-correlator for the Yuan Tseh Lee array for microwave background anisotropy

This paper reports the laboratory design and implementation of a four-antenna digital spectro-correlator for the Yuan Tseh Lee Array for Microwave Background Anisotropy (AMiBA). The system comprises four 5 Giga-samples/s (Gs/s), 8-bit analog to digital converter (ADC), and four Reconfigurable Open Architecture Computing Hardware 2 systems (ROACH2). The 5 Gs/s ADC board was designed by the authors, and the ROACH2 platform was manufactured by the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) community. The system has a bandwidth of 1.6 GHz, 128 spectral channels, an FX-type correlator, one polarization, and four antenna inputs. The correlation accumulators report the cross-correlation results of the six baselines, as well as the autocorrelation results of the four antennas. The system is planned to be characterized according to the results of various experiments before deployment: Allen deviation, optimal input power of the system, and confirmation of the correlator coefficient of the system. The new digital system is intended to replace the old analog system, which has no spectral information. This new system enables the AMiBA for new scientific missions, such as CO intensity mapping.