Noise performance of a phased-array feed composed of thick Vivaldi elements with embedded low-noise amplifiers
Bibliographic record
Abstract
Phased-array feeds (PAFs) can provide multi-beam capability for reflector antennas at microwave bands. For radio astronomy applications it is critical that the effective noise temperature of the PAF system be as low as practicable to be competitive with more conventional optimised single-beam systems. We describe our efforts to reduce the noise of a Vivaldi-element array by three means. The first is increase the thickness of the element to 5 mm, thereby increasing the surface area of the element, reducing surface current densities, resulting in lower resistive loss. The second is to eliminate dielectric materials wherever possible, enabled by the self-supporting nature of this design. Lastly, having thick elements permits low-noise amplifiers to be embedded within the antenna element, eliminating the lossy transmission line link between the LNA and the element feed point. To demonstrate these improvements a 41-element array has been constructed with an analogue beamformer to combine the central 9 elements. Y-factor measurements using free-space hot and cold loads show a minimum array noise temperature less than 35K.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".