EVLA FeedFE PDR

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EVLA FEEDS DESIGN

• S. Srikanth
• NRAO/Charlottesville

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VLA Cassegrain Geometry Drawing
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Current Receiver Bands
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VLA Vertex Feed Cone
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EVLA Receiver Bands
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Selection of Bands

• Minimize number of receivers
• Use existing technology
• Performance at the band edges - feeds,
  polarizers, amplifiers etc.

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Selection of Feed Type and Parameters

• Nominal taper of -13 dB at 9.25 degrees
• Compact horns where space is limited
• Ring-loaded slots (except for Q-band)
• Number of corrugations/wavelength - 3.8

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Conventional Corrugations
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Ring-Loaded Corrugations
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VSWR Conventional and Ring-Loaded
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Linear Taper Horn 75" OD 1.0 GHz
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Linear Taper Horn 75" OD 1.4 GHz
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Comparison of 75" OD and 62" OD Feeds
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Compact Horn 75" OD 1.0 GHz
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Compact Horn 62" OD 1.0 GHz
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Compact Horn 75" OD 1.4 GHz
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Compact Horn 62" OD 1.4 GHz
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VLA Cassegrain Geometry Drawing
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ANALYSIS METHODOLOGY
 
 
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ANALYSIS METHODOLOGY
6. Grids on the reflector surface
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Comparison of Subreflector Patternsat 1.5 GHz (?
0)
JPL Software
NRAO Software
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Comparison of Subreflector Patternsat 1.5 GHz (?
90)
JPL Software
NRAO Software
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Comparison of Main Reflector Patternsat 1.465 GHz
NRAO Software
-4 -2 0 2 4
Measured
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Subreflector Scatter Pattern 1.4 GHzCompact
Horn - 75" ODSymmetric Plane
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Subreflector Scatter Pattern 1.4 GHzCompact
Horn - 62" ODSymmetric Plane
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Subreflector Scatter Pattern 1.4 GHzCompact
Horn - 75" ODAsymmetric Plane
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Subreflector Scatter Pattern 1.4 GHzCompact
Horn - 62" ODAsymmetric Plane
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Subreflector Scatter Pattern 1.4 GHzCompact
Horn - 62" ODSymmetric Plane
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Subreflector Scatter Pattern 1.4 GHzCompact
Horn - 62" ODAsymmetric Plane
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Main Reflector Pattern 1.4 GHzCompact Horn -
75" OD
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Main Reflector Pattern 1.4 GHzCompact Horn -
62" OD
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Comparison of 75" OD and 62" OD Feeds
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Compact Horn 75" OD
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Compact Horn 62" OD
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Comparison of 75" OD and 62" OD Feeds
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Comparison of 75" OD and 62" OD Feeds
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Comparison of 75" OD and 62" OD Feeds
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The hybrid lens feed
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Measured Pattern Current Feed
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Corrected Pattern Current Feed
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Measured Pattern Current Feed
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Corrected Pattern Current Feed
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Comparison New Design Current FeedL-Band
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Comparison New Design Current FeedL-Band
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Comparison New Design Current FeedL-Band
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Comparison New Design Current FeedL-Band
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Comparison New Design Current FeedL-Band
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Comparison New Design Current FeedL-Band
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Comparison New Design Current FeedL-Band
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Subreflector Scatter Pattern 3.0 GHz-11 dB
Taper
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Subreflector Scatter Pattern 3.0 GHz-18 dB
Taper
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Gain/Tsys Analysis
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Gain/Tsys Analysis
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Gain/Tsys Analysis
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EVLA Predicted Performance
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Future Work