cold front end
DESCRIPTION
COLD FRONT END. Stephen Muchovej Caltech. CONSIDERATIONS. RF System Itself Physical Considerations Packaging Mounting. RF System Requirements. Noise temps of < 50K from 1-18GHz 1% Amp Stability, 1 degree phase stability Polar accuracy: 15 dB isolation - PowerPoint PPT PresentationTRANSCRIPT
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COLD FRONT END
Stephen MuchovejCaltech
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CONSIDERATIONS
• RF System Itself• Physical Considerations• Packaging• Mounting
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RF System Requirements
• Noise temps of < 50K from 1-18GHz• 1% Amp Stability, 1 degree phase stability• Polar accuracy: 15 dB isolation• Ready in Fall – completely done by Summer 2013
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RF System
• Note: amp symbols are reversed.
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Horn Considerations - Spillover
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Horn Considerations - Cooling
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Possible Solution
Well-matched opticsLow spilloverFree Design
…only operates over factor of 6 in frequency. Means we have to split
the system
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Telescope Focus Point2m in front of platform.We can put the two systems side-by-side, and cool all components in a single dewar.
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Features• Better system temp ( <50K across whole band )• Perfect beam matching between two systems.• Lateral translation between
2 systems.• Need 15cm Vertical Translation between two feeds.• Needs to rotate to calibrate smaller dishes.
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Mount Proposal
• Replace the mechanism up there with a full, self-contained system that bolts
onto the ring platform.
• Uses tracks for linear (and vertical -- focus) translations with actuators.• Uses a gear for rotation
• Install whole rx system at once• Adjust y once on installation
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Mount Proposal
• Replace the mechanism up there with a full, self-contained system that bolts onto the ring platform.
• Allows for rotation and translation
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Prime Focus Inventory•Rx and cryo lines.•Temp Controlled (TECA) box with:•Bias for amps•Temp Stable noise source•Temp monitoring•RF switch•Pre-amp module•RF-optical converter•Ethernet Switch•Ethernet controllable power supply•Small computer to control Noise Diode, Bias, and Alignment jig (rotation, x, and z)
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TimelineOther people involved are Tomi Hovatta
(most machining) and Russ KeeneyMarch-Mid May: Component Selection and Costing, Rx
Design, and Support Jig DesignMay 15: Order RF components, Quotes on Machining
(that won’t happen here)May-July: Machining (Jig, horns, cryostat), control
subsystem developmentAugust-September: Rx construction, Mechanical testing
of Jig, Rx TestingOctober: Buffer Month.Nov-Dec: Installation/Commissioning
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Still to define1. Communications between small
computer and control system2. Amount of focus shift in
pointing the telescope3. Tolerances for Rx placement --
laterally and rotationally4. Control of focus mechanism
(distortion of dish)5. Budget.