VLBA New Digital Architecture
The VLBA New Digital Architecture (VNDA) is the next generation upgrade to the highly productive Very Long Baseline Array (VLBA) operated by National Radio Astronomy Observatory (NRAO). The VNDA Channelizer is used to digitally filter the radio signals at each of the 10 VLBA sites.
The VNDA Channelizer interfaces with the VNDA Sampler, which outputs four digitized (single-polarization) sub-bands, each with a bandwidth of 1024 MHz and quantized with 16 bits per sample. The data acquisition rate is 131 Gb/s.
At each VLBA site, the VNDA Channelizer executes on a single server equipped with dual 100Gb NICs, four RTX A4000 GPUs, and 256 GB of RAM.
The VNDA Channelizer acts as a digital filter; it outputs between 1 and 32 channels, each selected from any of the four input bands, with output channel bandwidths selectable from 1 to 1024 MHz (in factor-of-two steps). The channelized data are re-quantised using 2, 4, or 8 bits per sample and broadcast as a stream of VDIF format UDP packets.
In parallel, the VNDA Channelizer measures and reports the statistics of the “on” and “off” states of the synchronously switched noise source that is superposed with the astronomical signal.