# Steer a beam with a dielectric cover

Channel: development; package: 2.0.0rc1; source: 2c32b7cf79b796fae825bfa08fc73d9914e61723

Page: https://remilab.ai/rfx/gallery/beam-steering/
Source: https://github.com/bk-squared/rfx/blob/2c32b7cf79b796fae825bfa08fc73d9914e61723/docs/public/gallery/beam-steering.mdx

A dipole radiates above a metal reflector. A patterned dielectric cover changes
the phase of the outgoing field across the aperture. This example connects that
material pattern to the direction of the main radiation lobe.

Historical design visualization. This is the 441-latent-variable trajectory on a wavelength/20 mesh. The plotted response is directivity; it does not establish realized gain, efficiency or broadband performance.

  ![Video poster](https://remilab.ai/rfx/gallery/assets/showcase-20260927/steer_traj.jpg)

    [source](https://remilab.ai/rfx/gallery/assets/showcase-20260927/steer_traj.mp4)

    [Download the trajectory](https://remilab.ai/rfx/gallery/assets/showcase-20260927/steer_traj.mp4).
  
  Left: the dielectric cover's relative permittivity. Center: a directional radiation cut. Right: objective sensitivities to latent design variables, ∂L/∂latent, not to physical permittivity ∂L/∂εr. Each frame is a design iteration, not a field time step.

## Read the model

| Part | Meaning |
|---|---|
| Radiator | An electric dipole above a metal reflector |
| Design region | A dielectric cover above the source |
| Parameterization | A latent grid mapped into a spatial permittivity field |
| Measurement | A near-to-far-field transform and an angular directivity cut |
| Objective | Concentrate radiation toward the selected direction while penalizing other directions |

A radiation cut shows how intensity varies with angle. Directivity compares
directional intensity with total radiated power; it does not include every loss
or mismatch that would enter realized gain.

## Follow the descent

  ![Video poster](https://remilab.ai/rfx/gallery/assets/showcase-20260927/steer_descent.jpg)

    [source](https://remilab.ai/rfx/gallery/assets/showcase-20260927/steer_descent.mp4)

    [Download the descent view](https://remilab.ai/rfx/gallery/assets/showcase-20260927/steer_descent.mp4).
  
  A complementary historical optimization view. Keep its drawn values with its own mesh and parameterization; the presentation's finer-mesh summary and full-cell design are separate results.

## Run the related example

The versioned [beam-steering source](https://github.com/bk-squared/rfx/blob/a9054338616b91bb1364699882c2530fa29a0048/validation/tmtt_paper/beam_steering_superstrate.py)
provides a short CPU setup. Run it from a matching source checkout with the example
dependencies installed:

```bash
python -m pip install -e ".[optimization]"
SMOKE=1 JAX_PLATFORMS=cpu PYTHONPATH=. python validation/tmtt_paper/beam_steering_superstrate.py
```

The short setup uses a coarse mesh and a few optimizer steps. It exercises the
source workflow and produces a pattern figure; it does not reproduce the archived
latent-variable movie or validate its numerical values.

**Try changing:** the initial cover profile or target direction. Check the whole
pattern, total-power normalization and collection-surface placement. See
[Far-field & RCS](https://remilab.ai/rfx/measure/far-field-and-rcs/) for the measurement and
[Gradient behavior](https://remilab.ai/rfx/guide/gradient-behavior/) for differentiation limits.

## Evidence and provenance

The exact simulation source revision is not established by the public media
bundle. The clips preserve presentation-era results; no new mesh, time-record
or independent-solver validation accompanies them. Raw latent histories and
field arrays are not included. In particular, a falling objective alone does
not establish the accuracy of the final RF design.

[Media catalog and SHA-256 hashes](https://remilab.ai/rfx/gallery/assets/showcase-20260927/media-catalog.json) ·
[Support Boundaries](https://remilab.ai/rfx/support/) ·
[Visual manual](https://remilab.ai/rfx/gallery/visual-manual/)