dishes with wide band single pixel feeds
TRANSCRIPT
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Disheswith
Wide Band Single Pixel FeedsP. Dewdney
WP2 meetingOct 18, 2011
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Wideband Single‐Pixel Feeds(WBSPF): Contributors• US TDP funded investigations
• Several different feeds designed and investigated• German Cortez (Cornell University)• Sandy Weinreb (Caltech)• Bill Imbriale (JPL)• Jack Welch, Dave de Boer, et al (ATA)
• Chalmers University • Miroslav Pantaleev, Per‐Simon Kildal, et al.• Long heritage of work on wide band feeds• Collaborated with TDP• On‐going investigation on Eleven Feed
• Herzberg Institute (NRC Canada) & U. Victoria• Log‐periodic log‐spiral• Stephane Claude, Jens Bornemann, et al
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WBSPF: Definition
• SKA Baseline design: corrugated horn feeds • Bandwidth ratios ~2:1
• Feeds with bandwidth ratios approaching >>2:1.
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WBSPF Options
• A Quad‐ridged feed design being developed at Cal Tech• Improvement of the Lindgren feed sold by ETS‐Lindgren
• QSC feed• Measured input match better that ‐10 dB over 10:1 bandwidth.
• ATA feed• Ultra‐wide band log‐periodic feed developed for the Allen Telescope Array• High gain• Frequency coverage in excess of 15:1• Measured performance
• The Eleven feed • Compact feed based on a parallel folded dipole configuration over a ground plane.• Measured data.
• Directional Log Periodic Log Spiral Antenna • University of Victoria & HIA, Canada.
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Eleven Feeds (Chalmers)
• On‐going work at Chalmers University on this feed.• Emphasis on compact, coolable feed to operate from 1.2 –10 GHz (folded design).• By reducing bandwidth ratio to 4:1, try to approach the performance of a corrugated horn.
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WBSPF: Comments
•WBSPF Advantages for SKA:• Potentially lower total system cost than multiple corrugated horns• instantaneous bandwidth coverage is much greater
• Disadvantages• No clear science requirement for instantaneous wide band (10:1) coverage has been identified.
• Note: on a single dish a WBSPF may have an advantage• A/T of dishes typically lower (see following slides).• Large instantaneous bandwidth to be sent & processed:
• would be required only if the entire band is transmitted.• Other issues:
• Most (not all) WBSPFs require wide opening‐angle optics (low gain), whereas horn feeds tend to be higher gain.• In offset design, this can be altered by adjusting the sub‐reflector.
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Wide Band Single Pixel Feeds considered
QSC Feed
ATA FeedLindgren Feed
Eleven Feed
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Wide Band Single Pixel Feeds considered
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Ring Loaded Corrugated Horns:15‐m Offset Gregorian
From Cortez et al.
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Ring Loaded Corrugated Horns:15‐m Offset Gregorian
7.0 m2/K
From Cortez et al.
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Quad Ridge:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
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Eleven Feed:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
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QSC‐i Feed:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
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ATA:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
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Log Periodic‐Log Spiral:15‐m Offset Gregorian
From Cortez et al.
7.0 m2/K
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