# A dielectric taper for a guided wave

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

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

A guided wave meets a higher-permittivity dielectric load. A transition made of
short dielectric sections gives the wave a gradual change of environment. This
example asks how the section permittivities change the reflected-wave spectrum.

Historical design visualization. These films preserve a presentation-era run. They have not been regenerated with the documentation source revision and do not establish current RF accuracy.

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

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

    [Download the trajectory](https://remilab.ai/rfx/gallery/assets/showcase-20260927/taper_traj.mp4).
  
  Read left to right: relative permittivity along the guide, reflection magnitude across frequency, and the objective's sensitivity to each section's permittivity. The movie advances through optimization iterations, not physical time.

## Read the model

| Part | Meaning |
|---|---|
| Guide | A rectangular metal-walled guide with absorbing ends along propagation |
| Load | A dielectric-filled continuation of the guide |
| Design | A sequence of dielectric sections ahead of the load |
| Excitation and measurement | The guided mode and its reflected port response |
| Objective | Band-averaged reflected power |

The current [research source](https://github.com/bk-squared/rfx/blob/a9054338616b91bb1364699882c2530fa29a0048/validation/tmtt_paper/waveguide_dielectric_taper.py)
distinguishes its geometries: the short CPU setup realizes WR-90 dimensions,
while the paper meshes realize a 23 mm broad wall rather than the nominal
22.86 mm. Its reported paper responses belong to those realized guides.
The legacy [empty-guide example](https://remilab.ai/rfx/gallery/waveguide_wr90/) is a different model.

## Watch the objective evolve

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

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

    [Download the descent view](https://remilab.ai/rfx/gallery/assets/showcase-20260927/taper_descent.mp4).
  
  A complementary view of the recorded design history. The comparison curve is part of the historical figure; this page makes no claim of superiority over a classical taper.

## Run the related example

In a source checkout matching the linked revision, install the project's example
dependencies and run its documented CPU setup:

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

This short run produces an initial/optimized response and material-profile figure.
It exercises the workflow; it does not reproduce these archived movies or the
full-resolution paper result. Read its preflight output and realized dimensions.

**Try changing:** the initial permittivity profile or number of sections. Compare
the complete reflection curve and keep the guide, ports and frequency band fixed.
See [Waveguide Ports](https://remilab.ai/rfx/guide/waveguide-ports/) and
[Inverse Design](https://remilab.ai/rfx/design/optimization/) for the API path.

## Evidence and provenance

The videos show a recorded optimization and retain the numbers drawn in their
original frames. Their exact simulation source revision is unavailable in the
public media bundle. The linked source is a related, versioned example, not a
reproduction certificate for these assets. Raw iteration arrays are not included.
Current accuracy and differentiation support follow
[Support Boundaries](https://remilab.ai/rfx/support/), including mesh and time-record
checks before making a new numerical claim.

[Download the media catalog and SHA-256 hashes](https://remilab.ai/rfx/gallery/assets/showcase-20260927/media-catalog.json).
Next: [tune a microstrip notch](https://remilab.ai/rfx/gallery/microstrip-notch/) or
[read the visual manual](https://remilab.ai/rfx/gallery/visual-manual/).