Array-Fed Radiometer · 2020. 7. 9. · Array-Fed Radiometer Presenter & PI: Jeffrey Piepmeier,...
Transcript of Array-Fed Radiometer · 2020. 7. 9. · Array-Fed Radiometer Presenter & PI: Jeffrey Piepmeier,...
Array-Fed RadiometerPresenter & PI: Jeffrey Piepmeier, NASA Goddard
Team Members: Jared Jordan, Will Stacy (Cubic | Nuvotronics); Thomas Holmes, Paul Racette, Victor Marrero, Ali Mahnad, Rafael Rincon, Giovanni De Amici, Jinzheng Peng (GSFC)Program: ACT-17
Problem to Solve: Spatial Aliasing166 GHz @ 0.5 meter
Nyquist Sampled166 GHz @ 1 meter
Under Sampled
37 GHz @ 2 meterNyquist Sampled
37 GHz @ 2 meterUnder Sampled
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Improving Conventional Sampling Approach
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36 GHz
89 GHz
18/23 GHz
10 GHz
Scan N, N+1s/c motion
12.7 km/scan
19 x 32 km
11 x 17 km
4 x 7 km
9 x 15 km
2 x 4 km
6 x 9 km
Use full aperture,but still under sampled
Add more beams for Nyquist Sampling
X
XK
K
KaKaKa
W
Notional Feed Cluster for Nyquist
SamplingWhat if ?
Pushes feeds more off focus!
How: Borrow (steal) from Radio Astronomy
• Possibilities• Multiple beams• Beam steering• Beam shaping• RFI nulling
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XOverlapping feed apertures at multiple frequencies -> broadband phased array feed
Reinventing Radio Astronomy – PAF TechnologyJohn O’SullivanCentre for Astronomy and Space ScienceCSIRO2 April 2013
http://www.astron.nl/ava2013/documents/John_O_Sullivan.pdf4
- Dual-Polarized 8X9 Vivaldi array constructed on a 2 mm pitch.
- Targeting operation at 5 radiometer bands spanning 10.6-92 GHz within a single aperture.
- Assembled from 17 pieces of stacked PolyStrata®
radiator/array processing cards.- Column combiners used to
perform analog beamforming in elevation.
- Boresight and azimuth steered patterns formed by digitally combining card patterns in post-processing.
- Excellent correlation between simulated and measured radiation patterns is achieved across all radiometer bands.
- Elimination of traditional connector interface between dual-polarized array and array processing.
Technical Details X-W band PolyStrata® Array Demonstrator
© 2017 Nuvotronics, Inc.
S21Noise Floor
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Laboratory Demonstration
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Seven Nyquist-Sampled Beams
80 cm
Agile Beamforming in Reprocessing
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Weights (dB, degrees)“Max SNR” beamformer used in radio astronomy
Next Steps
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Accomplishments:- Development of broadband (4:1 & 10:1) dual-polarized apertures spanning X-band to W-band.
- Low-loss (< 0.5 dB) element-level diplexing to finely control frequency-dependent aperture radiation at the “pixel” level with low-loss (e.g. 0.04 dB/mm @ 89 GHz) analog beamforming networks.
- Modular, multi-band, coaxial-based, passive front-end hardware to enable multi-function instrumentation (i.e. radiometer, radar, fixed & scannable apertures)
Where we are headed:- Elimination of traditional lossy and bulky RF connector interfaces & cabling and tighter
integration of active devices (i.e. LNAs, diode detectors, ADCs, etc.) with passive front-end hardware to form tile-able instrumentation.
- Near-term: Trade fewer frequency bands for a lower SWAP instrument and faster deployment within a small satellite payload.
- Long-term: Continue the technology development to further enable multi-frequency, multi-beam instrumentation from a common aperture.