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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

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Cold front end

COLD FRONT END

Stephen Muchovej

Caltech


Considerations

CONSIDERATIONS

RF System Itself

Physical Considerations

Packaging

Mounting


Rf system requirements

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


Rf system

RF System

Note: amp symbols are reversed.


Horn considerations spillover

Horn Considerations - Spillover


Horn considerations cooling

Horn Considerations - Cooling


Possible solution

Possible Solution

Well-matched optics

Low spillover

Free Design

…only operates over factor of 6 in frequency.

Means we have to split the system


Telescope focus point

Telescope Focus Point

2m in front of platform.

We can put the two systems side-by-side, and cool all components in a single dewar.


Features

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.


Mount proposal

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


Mount proposal1

Mount Proposal

Replace the mechanism up there with a full, self-contained system that bolts onto the ring platform.

  • Allows for rotation and translation


Prime focus inventory

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)


Timeline

  • Other people involved are TomiHovatta

  • (most machining) and Russ Keeney

  • March-Mid May: Component Selection and Costing, Rx Design, and Support Jig Design

  • May 15: Order RF components, Quotes on Machining (that won’t happen here)

  • May-July: Machining (Jig, horns, cryostat), control subsystem development

  • August-September: Rx construction, Mechanical testing of Jig, Rx Testing

  • October: Buffer Month.

  • Nov-Dec: Installation/Commissioning

Timeline


Still to define

  • Communications between small computer and control system

  • Amount of focus shift in pointing the telescope

  • Tolerances for Rx placement -- laterally and rotationally

  • Control of focus mechanism (distortion of dish)

  • Budget.

Still to define


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