1 / 27

NRAO Receivers

NRAO Receivers. Richard Prestage. (Marian W. Pospieszalski, Steve White, Steve Durand). Noise Temperature Summary of Cryogenic HEMTs. M min Prediction (1991) and State of the Art (2009). VLA/EVLA T Rx versus Frequency. T Rx = m · F + b ; m = 0.5 º K/ GHz ; b = 8 º K.

maxim
Download Presentation

NRAO Receivers

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NRAO Receivers • Richard Prestage • (Marian W. Pospieszalski, Steve White, Steve Durand)

  2. Noise Temperature Summary of Cryogenic HEMTs ALMA Workshop, March 21-22, 2011

  3. Mmin Prediction (1991) and State of the Art (2009) NRAO Cryogenic Amplifiers

  4. VLA/EVLATRx versus Frequency TRx = m·F + b ; m = 0.5ºK/ GHz ; b = 8ºK NRAO Cryogenic Amplifiers

  5. The RF Signal Path The Feedhorn: Compact corrugated horn.

  6. The RF Signal Path A top view of the 15K cold plate and RF signal path: The input to the cryostat. The charcoal trap, the heaters and the thermostat.

  7. The RF Signal Path(cont.) The thermal gap and OMT assemblies: Foam window. Gap set to 5mils. The full assembly forms the circular-to-square transition, the square to quad-ridge taper and the quad-ridge to coaxial sections.

  8. The RF Signal Path(cont.) The RF Tree: Thermal gap/RF choke. Ortho-mode transducer. 90°Quadrature hybrid coupler. Cryo-isolator and calibration coupler. Three stage NRAO Cryo-3 InP HFET low noise amplifier.

  9. Receiver Characterization

  10. K Band Focal Plane Array(Shanghai) Steven D. White*, Matt Morgan, Felix J. Lockman, Eric Bryerton, Glen Langston, Roger Norrod, Bob Simon,Galen Watts, Sivasankaran Srikanth, Gary Anderson

  11. System Baseline Specifications

  12. Bandwidth Limitations

  13. GBT K-Band Array Amplifiers at 19 K Green Bank, West Virginia, January 11, 2009

  14. Feedhorn Arrangement • GBT: • 36” mounting ring on the receiver turret would support about 60 K-Band feedhorns. • 3.45” spacing (~2.5 HPBW) • Shanghai: • Feed Design. • Efficiency ? • Spacing? • Mechanical Impact.

  15. Compact Corrugated Feedhorns 3.4” O.D. Feedhorns 22 GHz Telescope Beams

  16. Thermal Gap • 0.543" circular waveguide • 0.010" gap with choke groove • upper half at 300 K, lower at 15 K • hollow, shaped G10 supports • optimized for weight, strength, and thermal isolation • Cuming Microwave PS-102 foam for vacuum seal • Cuming Eccobond 45 epoxy • 3-mil Kapton vapor seal

  17. Quadrature Phase Shifter and OMT

  18. Noise Calibration Source Integrated With Coupler

  19. KFPA Uses Existing EVLA Low-Noise Amplifier Design

  20. Gapped WR42 Sliding Waveguide Output Transition • 0.360” maximum travel • ∆ length on cool-down: ~0.144” • Stable at final temperature • Chomerics 1285 conductive elastomer • Ecco-foam PS102 with 3 mil Kapton

  21. Sliding Waveguide/Thermal Gap Assembly Thermal Gap and 20 cm SS waveguide: 1.7 Watts 1st Stage Load. 30 cm SS coax: 0.54 Watts 1st Stage Load. Total: 1st Stage 18 W; 2nd Stage 3 W. Contraction from 300K to 15K is ~ 4.1 mm of total 6.35 mm.

  22. Downconverter Size Dominated by DC Control Functions PCB Side MMIC Side

  23. Snakes of Star Formation KFPA NH3 (1,1) contours on Spitzer Glimpse Image The Galaxy is rich in Snakes of star forming clouds: Finn and Jackson, in preparation.

  24. Langston, Batistti, Jones 2011, in preparation Also see posters by Batistti et al and Jones et al

  25. The National Radio Astronomy Observatory is a facility of the National Science Foundationoperated under cooperative agreement by Associated Universities, Inc. www.nrao.edu • science.nrao.edu

More Related