A Single-FPGA Real-Time Dual Beam-Former With FX Correlation Capabilities: First Results at the Nançay Radio Telescope With the FAN Antenna Array

A full-time beam-former for two independent antenna groups, with visibility computation capabilities at a slower rate, has been formerly designed on a single FPGA for the BAO-radio instrument, a radio telescope demonstrator for the study of dark energy by the observation of Baryonic Acoustic Oscillations (BAO) spectrum with HI probing technique. On the same hardware platform, a firmware, dedicated for the Focal Array at Nançay (FAN) project, can provide a full-time dual beam-forming on a single antenna array. It can process an incoming data flow of twelve channels, each organized as complex spectrum (2 × 8 bits) of 4096 frequencies with a 4 GbPS effective rate. The dual-beam capability of the system has been successfully tested on the FAN array with transits on the radio sources CasA and 3C123, the beam-former being configured by complex coefficients computed from a previous off-line software correlation on CasA. Recently, another beam-forming on 3C123 has been done after a calibration on CasA performed by the beam-former itself, set in correlation mode, and a source-tracking.