Real-time Tbps digital correlator in NTU-array

Abstract

NTU-Array is a W-band, dual-polarization, 6-receiver interferometer telescope aiming to detect the cross-over of CMB primary and secondary anisotropies. The telescope has 34Ghz instantaneous bandwidth for the continuum observation. The ultra-wide bandwidth is down-converted to four base-bands of 0-8.7Ghz for the ensuing digital correlation. We have completed the development of an FX digital correlator system for NTU-Array, which utilizes 18Ghz, 1-bit samplers for digitization and Virtex-4 FPGAs for subsequent digital processing of Fourier transformation and cross-correlation. This new digital correlator has 275Mhz frequency resolution and is processing in real time the 850 Gbps input data at power consumption about 1 KW. We stress that our present setup substantially under-rates this FPGA computing machine, as it is designed to process 2.5 Tbps input data in real time from 18Ghz, 3-bit ADCs. Verification of this new digital correloator has been completed, and it demonstrates that the correlator can detect small signals with -40db S/N within one second integration per frequency channel.