Alma front end beam efficiency evaluation
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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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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


Far field beam patterns

80% typical aperture efficiency


Aperture Efficiency

No central blockage


Beam pointing I


Beam pointing II

X and y axes are beam

offsets in degrees

Red – Pol 0

Green Pol 1

Blue secondary mirror

angular dimensions


Focus offset (x,y)


Beam squint


Defocus


Co-polar


Cross -polar

-19dB peak, -18dB total power


Far field cross pol ratio

Red = -10dB

4 dB contour


NA FEIC data b9, near field

Lambda/4 compensation off


NA FEIC data b9, near field

Lambda/4 compensation needs to be looked at


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


NA FEIC b7 data, near field


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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