Design Of Pharos2 Phased Array Feed

We describe the design and architecture of PHAROS2, a cryogenically cooled 4-8 GHz Phased Array Feed (PAF) demonstrator with digital beamformer for radio astronomy application. The instrument will be capable of synthesizing four independent single-polarization beams by combining 24 active elements of an array of Vivaldi antennas.PHAROS2, the upgrade of PHAROS (PHased Arrays for Reflector Observing Systems), features: a) commercial cryogenic LNAs with state-of-the-art performance, b) a "Warm Section" for signal filtering, conditioning and single downconversion to select a 275 MHz Intermediate Frequency (IF) bandwidth within the 4-8 GHz Radio Frequency (RF) band, c) an IF signal transportation by analog WDM (Wavelength Division Mutiplexing) fiberoptic link, and d) a FPGA-based Italian Tile Processing Module (iTPM) digital backend.PHAROS2 will be mounted at the primary focus of the 76-m diameter Lovell radio telescope (Jodrell Bank Observatory, UK) for technical and scientific validation.