Reflectarray performance improvement using the element spacing reduction technique
Bibliographic record
Abstract
This thesis presents the design, analysis and performance improvement of reflectarray (RA) antennas. The considered RA consists of a feed antenna and an array of 'small' elements that are distributed on a flat surface using printed circuit technology. The feed antenna is used to generate an incident field to illuminate the elements of the RA. Each element acts as a partial reflector with a specific reflection coefficient. The resulting reflected field on the RA aperture should have the desired amplitude and phase distribution to create the antenna`s far field radiation pattern. The RA element reflection coefficient versus its geometrical parameters in a uniform infinite array environment is used as a data table to design the RA elements. The RA element geometry is comprised of a simple rectangular patch on the top of a at single-layer grounded dielectric substrate. Reflectarray technology suffers from several degrading factors such as low efficiency and gain bandwidth. In this thesis it is shown that as the element spacing reduces, a better control over the RA aperture is achieved. This improves the efficiency of the RA. Also, as the element spacing reduces, the reflection coefficient phase versus frequency becomes more linear. This improves the gain bandwidth of the RA. The beam squint, which is the deviation of the RA beam angle from the desired beam angle, is another degrading factor of the RA technology. Only a few attempts have been made in the literature to investigate or reduce the RA beam squint. These attempts are either incomplete or complicated. In this thesis, it is shown that as the element spacing reduces the beam squint of the RA improves. It is also shown that as the element spacing reduces the side lobe level and cross-polarization of the RA improves. These two far field parameters are important but not investigated in the literature. Sixteen RA designs and associated analyses are presented. One design was selected for fabrication utilizing a feed antenna from the University of Manitoba's Antenna Laboratory. The measured radiation patterns agree well with the analysis results and demonstrate the validity of the element spacing reduction technique.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.002 |
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".