Gbt k band focal plane array
This presentation is the property of its rightful owner.
Sponsored Links
1 / 11

GBT K-band Focal Plane Array PowerPoint PPT Presentation


  • 47 Views
  • Uploaded on
  • Presentation posted in: General

GBT K-band Focal Plane Array. Monitor and Control Interface, Cryogenic LNA Bias System February 27, 2008. Existing Bias Technology KFPA Requirements. Cryo LNA Bias Cards 4 or 6 bias channels/card, screwdriver adjusted Vdrain and Vgate, servo Idrain.

Download Presentation

GBT K-band Focal Plane Array

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Gbt k band focal plane array

GBT K-band Focal Plane Array

Monitor and Control Interface,

Cryogenic LNA Bias System

February 27, 2008


Existing bias technology kfpa requirements

Existing Bias TechnologyKFPA Requirements

  • Cryo LNA Bias Cards

    • 4 or 6 bias channels/card, screwdriver adjusted Vdrain and Vgate, servo Idrain.

    • Card caged, each card 8.5 x 4.5 x 0.5”, 28 in 3 sp. – 19” Rack.

    • 2 wires per amp stage plus ground via hermetic feedthrough.

  • KFPA will have 61 pixels, 2 polarizations, 4 amp stages:

    • 488 Vdrain, 488 Vgate, 122 LED lines, plus grounds.

    • 82 – 6 channel cards, 12 rack spaces (21”)

    • 1220 pin hermetic feed through including LEDs and grounds

  • Decision:

    • Bias regulators inside the dewar, adjust them remotely.

    • LNA Bias becomes more dependant on M+C


Existing nrao m c technology

Existing NRAO M+C Technology

  • VLBA Standard Interface Board

    • 256 Control bits, 256 Monitor bits, 64 Analog channels

    • 8032 @ 11 MHz

    • RS-485 @ 57k

  • GBT Gregorian Receiver Interface

    • 48 Control bits, 50 Monitor bits, 56 Analog channels, 8 Analog sources

    • 8052 @ 11 MHz

    • RS-485 @ 57k

    • RF attenuating enclosure, filtered connectors, 12 x 7 x 4”

    • Analog channels are 12 bits


Kfpa monitor and control needs

KFPA Monitor and Control Needs

  • ~2000 Analog monitor points

    • 488 Cryo LNA stages, Vd, Id, Vg

    • 61 Noise cal Id, plus overall Vd, Vg

    • 61 I-LED

    • 61 Down Converter LO levels, Amplifiers bias

    • 15K, 50K, 300K, Vacuum, Power Supplies

  • >7000 Digital M+C points

    • 61 Down Converter Attenuators x2, 4-5 bits

    • 488 Cryo LNA stage bias settings, 8 bits

    • 61 LED On/Off

    • Cryo state, S/R, Cal State…

  • Thousands of wires, 1-2m long.


Kfpa monitor and control needs1

KFPA Monitor and Control Needs

  • Increase Monitor and Control distribution

    • Build M+C capability into individual receiver modules.

    • Use serial lines for communication with modules.

    • Ethernet to GBT Network with COTS single board as go-between.

  • Benefits

    • Fewer dewar feed throughs.

    • No long line problems.

    • COTS: Inter-Integrated Circuit (IIc, I2C, I2C).

  • Disadvantages

    • New for GB Receiver

    • Interference, Clock runs at 400 kHz


Cryogenic lna bias alma 40 04 02 01

Cryogenic LNA Bias, ALMA 40.04.02.01


Cryogenic lna bias

Cryogenic LNA Bias


Cryogenic lna bias1

Cryogenic LNA Bias

  • ALMA 40.04.02.01 Bias regulator circuit.

  • 8 - Dual, non-volatile, 8 bit, IIc potentiometers controlling voltage references to create Vdrain-set and Idrain-set for regulator.

  • Two 10 bit, 12 channel, IIc A/D converters, scaled, monitor Vd, Id, Vg, I-LED (drop two Vg measurements on later amp stages).

  • Each pixel enabled or isolated by IIc bus buffer, selected by IIc I/O Expander external to the pixel.

  • Bias and Monitor for both polarizations fits on 2 x 3” PC card, 61 cards and mother board fit in 9 x 9 x 4”.

  • Bias card array is contained in a pod off the dewar.


Monitor and control

Monitor and Control


Monitor and control1

Monitor and Control

  • Each module contains IIc A/D’s and I/O Expanders and is enabled or isolated by IIc bus buffer, selected by IIc I/O Expander external to the module.

  • Additional IIc M+C boards constructed for non-module monitor and control functions.

  • Multiple IIc busses isolate subsystems and decrease M+C scan time.


Summary and comments

Summary and Comments

  • Thousands of Monitor and Control points distributed over entire receiver chassis communicating via a serial bus instead of points wired to a central unit.

  • COTS single board computer interfaces between M+C nodes and GBT M+C System and is located outside the dewar.

  • RFI Mitigation:

    • We strongly advise not running M+C scans during observing scans, rather in between scans.

    • A/D converters will be set for external (bus) clock, single board computer is enclosed in an RF attenuating enclosure, low pass feed throughs will be used.


  • Login