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ALMA front-end beam efficiency evaluation

ALMA front-end beam efficiency evaluation. A.M. Baryshev NOVA/SRON/RuG. Outline. band 9 optics measurement system (example) Band 9 efficiency analysis NA FEIC data for band 9 and band 7 Q/A. The beam pattern measurement Set-Up. Typical near field measurements. Amplitude. Phase.

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ALMA front-end beam efficiency evaluation

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  1. ALMA front-end beam efficiency evaluation A.M. Baryshev NOVA/SRON/RuG

  2. Outline • band 9 optics measurement system (example) • Band 9 efficiency analysis • NA FEIC data for band 9 and band 7 • Q/A

  3. The beam pattern measurement Set-Up

  4. Typical near field measurements Amplitude Phase

  5. Far field beam patterns 80% typical aperture efficiency

  6. Aperture Efficiency No central blockage

  7. Beam pointing I

  8. Beam pointing II X and y axes are beam offsets in degrees Red – Pol 0 Green Pol 1 Blue secondary mirror angular dimensions

  9. Focus offset (x,y)

  10. Beam squint

  11. Defocus

  12. Co-polar

  13. Cross -polar -19dB peak, -18dB total power

  14. Far field cross pol ratio Red = -10dB 4 dB contour

  15. NA FEIC data b9, near field Lambda/4 compensation off

  16. NA FEIC data b9, near field Lambda/4 compensation needs to be looked at

  17. NA FEIC b9 far field Probe model: OEWG WR22: 33.00-50.00 GHz ? Aperture efficiency 63.3%, Phase center X, Y, Z: 1.32, -0.83, 289 (mm) (0,-0.94) Deg Aperture efficiency 65.1%, Phase center X, Y, Z: 1.32, -0.87, 292 (mm) (0, -1.40) Deg

  18. NA FEIC b7 data, near field

  19. NA FEIC b7 data, far field Aperture Efficiency 42.9, Phase center X,Y,Z -- 2.22, 5.92, 103.84 (mm)

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