The kat 7 feed package
Download
1 / 18

The KAT-7 feed package - PowerPoint PPT Presentation


  • 114 Views
  • Uploaded on

The KAT-7 feed package. 1. EMSS ?. A group of companies, operating from Stellenbosch, SA Employee-owned, 100 bodies, T/O ~ $M6 CEM code FEKO: www.feko.info EMSS Antennas (8 bodies) Contracted into MeerKAT project, cost-plus-material basis, shared risk

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' The KAT-7 feed package' - santos


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

EMSS ?

  • A group of companies, operating from Stellenbosch, SA

  • Employee-owned, 100 bodies, T/O ~ $M6

  • CEM code FEKO: www.feko.info

  • EMSS Antennas (8 bodies)

    • Contracted into MeerKAT project, cost-plus-material basis, shared risk

    • Self-representative on subsystem level

    • Develop and implement feed technology, act as custodians of EM issues

2


The kat 7 reflector revisited
The KAT-7 reflector: Revisited

  • Design freeze late 2007

    • D = 12m (project decision, based onSKA trends)

    • F/D = 0.38 (Calculated to suit typicalWBFs, also allowing a classicalhorn feed as fall-back)

    • Prime focus: Four struts, (+),~2/3 out, cross-section shaped tominimise spillover

    • Surface to be flame-sprayedAluminium or mesh, 1.5mm RMS

    • Drives: Elevation over azimuth

3



The kat 7 horn design freeze early 2008
The KAT-7 horn: Design freeze early 2008

  • Design briefs

    • 1200 – 1950MHz (48%)

    • Orthogonal linear polarisations

    • Optimise Ae / (Tspillover + X)

  • Results

    • Choked wide-angle horn, Ø = 1m (oversized)

    • Irises (for impedance matching af flower)

    • Theoretical TE11 mismatch: ≤ –33dB

    • Theoretical Tspillover: 5  2K

    • Theoretical illumination efficiency: 70  65%

5



Theoretical a e t sys no blockage
Theoretical Ae / Tsys (no blockage)

7



The kat 7 omt
The KAT-7 OMT

  • Design briefs (early 2008)

    • Smaller than typical bladed OMTs (to facilitatte small cryostat)

    • High-fidelity, no hybrid devices

  • Chosen candidate

    • Two crossed dipoles in shorted waveguide

    • Impedance-transforming feeder lines

    • Two Marchand baluns

    • Design method: Aggressive space mapping

9


The kat 7 omt size
The KAT-7 OMT size

  • Size does matter…

    • Final device quite small

    • 0.2λ3

    • Thus small cryostat areal possibility

    • Theoretical performancevery promising

    • (Typical quadridgestructures = 3 – 6 λ3)

10



The kat 7 horn pattern measurements
The Kat-7 horn: Pattern measurements

  • Pattern verification

    • 500m Ground-reflection far-field range

    • Principal planes and diagonal cuts made

    • Fed by prototype single-mode transducer

    • Found excllent agreement with CEM predictions

12




The kat 7 horn omt port properties1
The KAT-7 horn + OMT: Port properties

  • Loss?

    • Crude method: Short waveguide, divide insertion loss by two

    • Looks like 0.1+ dB

    • I.e., ~8K at ambient,and ~2K at 77Kphysical

    • Since verified by twoOMTs back to back,transmission –0.2dB,confirming 0.1dB loss

15


The kat 7 cryostat
The KAT-7 cryostat

  • Design briefs

    • Small vessel, robust

    • Stirling-cycle cryo-cooler

      • Sunpower GT unit: 15W at 77K (neck at 30°C)

      • Cold fluid up from pedestal, for cooling the cooler

    • No mechanical vacuum maintenance

      • Ion pump, carbon traps, limited cryo-pumping at 77K

    • Host to LNAs and noise injection circuitry

    • Life support from pedestal below

16



Conclusions
Conclusions

  • Good horn performance from prime focus

  • Very good performance from small OMT

  • Getting there with a small robust cryostat

  • Full development will be captured in a project memo, towards end of 2009

  • Thank you.

18


ad