NRAO/Socorro Colloquium Series
Neal Erickson
University of Massachusetts
A 64 Element Phased Focal Plane Array for 70-95 GHz
Conventional heterodyne focal plane arrays (or FPA’s) have significant limitations in their performance with large gaps between elements and relatively poor coupling to the antenna over wide bandwidths due to the variation in the illumination. FPA’s built utilizing phased array feed techniques can overcome these limitations and offer significant other performance enhancements. This approach uses a group of small antenna feeds to synthesize a single feed for the main antenna. Such an array of sufficient size can collect ALL of the energy in the focal plane, with Nyquist sampling. Phased combination of the elements of this focal plane array allows one to synthesize horns of optimal size and amplitude/phase distribution to enhance the telescope resolution and even compensate for telescope large scale errors.
Phased array receivers have been built in the cm bands but near 90 GHz the required wavelength-scale packing of elements makes them far more difficult to build. To demonstrate the technology, UMass and BYU are building an 8 × 8 array tuning the 70 – 95 GHz frequency range using a HEMT MMIC cryogenic front end, and a MMIC room temperature frequency converter. It uses entirely digital beam combining over an IF bandwidth of 50-100 MHz. Sensitivity of any single beam should be comparable to a conventional receiver using the same MMIC’s. The goal of this work is to install this array on the 100m Green Bank Telescope within a three year schedule. The long term goal is to show the feasibility of an array with ~1000 elements.
May 18, 2012
11:00 am
Array Operations Center Auditorium
All NRAO employees are invited to attend via video, available in Charlottesville Room 230, Green Bank Room 137 and Tucson N525.
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