Phased Array Feeds - Filling the focal plane

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19-element dual-polarization phased array feed (PAF) for L-band with cryogenic SiGe HBT LNAs. Measured Tsys of 35K on the Green Bank 20-meter telescope.  This PAF will be tested on the GBT in early 2013.

To increase the speed at which large areas of the sky can be surveyed, it would be hugely beneficial to more fully populate and sample the focal plane of large radio telescopes.  To see if this can be done without sacrificing raw sensitivity is the long-term goal of this CDL research effort.  A successful collaboration with Brigham Young University ended in 2012, during which a world record low noise for a PAF (phased array feed) of 35K was obtained at L-band (1.4 GHz) using a cryogenic PAF on the Green Bank 20m telescope.   The long-term goal is to determine the technical and cost viability of a 37-beam 1.4 GHz cryogenic PAF on the GBT with 25K noise temperature per beam—such a multi-beam receiver would dramatically increase the survey speed of the GBT.

In 2013, the current array will be moved to the GBT, where it will be tested and its performance compared to earlier measurements on the 20m telescope.  Design work will begin on a new Dewar to house a wider-spaced array better optimized for the GBT.  Development will continue on the DSP system and array simulations, including models of mutual noise coupling, which may ultimately limit the performance of PAFs.

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