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The Greenland Telescope (GLT)

IF Processor Chassis, GLT Project
Image Credit: Derek Kubo
IF Processor Chassis, GLT Project
Photo of the bottom side of two IF Processor chassis under construction in Hilo office. Visible are the four 0-2 GHz baseband channels, DC power supplies, and ADAM monitor and control. IF processing and down conversion sections are on the far side.
Each IF Processor unit accepts a pair of 4-8 GHz IF input signals from 3 receivers consisting of 86, 230 & 345 GHz. Selection of the receiver is via a pair of SP4T RF switches. Each of the 2 selected IF input signals are level controlled using a set of variable gain amplifiers, external power detectors, and software servo system. Heterodyne down conversion to 0-2 GHz baseband is performed using bandpass filters, mixers and a pair of LOs at 3.85 and 8.15 GHz to produce 4 outputs that represent 4-6 and 6-8 GHz. 4 sets of SPDT switches (upper gold components) allow for direct baseband inputs. A final set of signal leveling is performed at baseband using variable attenuators, external detectors, and software control. The four baseband outputs are provided to the distribution assemblies and then to the ROACH-2 units where the signals are digitized. Two IF Processor units were integrated into the GLT in Thule A.B. during summer 2017. These units were designed and constructed in the ASIAA Hilo Office by Ryan Chilson, software provided by Ranjani Srinivasan.
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