Digital receiver for the ALMA correlator Gianni Comoretto, B. Quertier, A. Gunst;
Osservatorio Astrofisico di Arcetri
The ALMA correlator uses a digital filterbank to increase spectral resolution with respect to the original time multiplexed architecture. The filterbank is composed of 32 tunable digital filters, with 2 GHz input bandwidth, and a decimation factor of 1/32 or 1/64. Each correlator 'plane' used for the 32 time demultiplexed input data flow can thus be used to process 32 subchannels across 2 GHz. The filterbank is implemented in 16 FPGAs. A prototype board, with 6 filters (3 FPGAs), has been completed and is currently under test.
The filter architecture, and its simulated performance, is presented. Nonlinear effects and stitching problems between adjacent subchannels are considered.