Arcetri Technical Report 2/2015

SKA Project Series
LFAA Tile Beamformer structure

G. Comoretto

INAF Osservatorio Astrofisico di Arcetri

Abstract

The LFAA tile processing modules (TPM) combine the signals from 256 dual-polarization antennas, in the frequency range 50-350 MHz, into a single station beam. Beamforming is done hyerachically, with the TPM first combining the 16 antennas that are processed in the module, using the Tile Beamformer described here, and then combining these partial beams into the station beam, using a daisy chain structure.

The Tile Beamformer receives antenna samples already channelized, with a channel spacing of 750 KHz, and align each antenna in the frequency domain using a phasor computed in real time from delay and delay rate informations. It is possible to select up to 16 idependent portions of the input frequency range, each one pointing in a different direction.

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 Arcetri Technical Report 4/2014

SKA Project Series
Structure and processing of the F section for SKA

G. Comoretto

INAF Osservatorio Astrofisico di Arcetri

Abstract

The three (Low, Mid and Survey) SKA correlators share a similar structure, with a FX architecture. The F part has a total of the order of 2 18 channels, with a dual stage filter-bank. The first stage provides channelization with overlapping channels, while the second provides non overlapping channels with good channel-to-channel insulation.

The channelization parameters (filter shape vs. filter complexity, overlapping amount, etc) are similar for the correlators, despite important differences in bandwidth, physical implementation, etc. We discuss these parameters, with considerations on the specificity of the three correlators.

The delay and fringe compensation functions are also implemented inside the channelizer, and are discussed here.

Pdf version of this report