A useful simulation has three views: the model you built, the fields it produces, and the quantity you want to measure. Keep those views together as you learn rfx.
1. Build the physical model
Choose a structure, material and excitation. Open radiation problems use absorbing boundaries; a closed conducting cavity uses reflecting metal walls. The boundary changes the physical problem, not just how a plot ends.
Begin with Quick Start, Core Concepts and Materials & geometry. Run preflight before the simulation and inspect the realized mesh: a drawn dimension need not land exactly on a grid plane.
2. Watch the fields
Read the field component, axes and color scale before reading the motion. A field slice shows one component on one plane; it is not the entire three-dimensional solution. Keep the color scale fixed when comparing times or designs.
| Animation type | What moves | What it can explain |
|---|---|---|
| Time-domain snapshots | Recorded fields at successive simulation times | Propagation, reflection, transient decay and interference |
| Phasor replay | The phase of a single-frequency complex field | Standing-wave structure and relative phase; it does not show pulse arrival |
| Design history | The geometry or material and response at each optimization step | How a design changes; interpolated frames do not add simulation samples |
| Stored parameter sweep | A selection of precomputed parameter values | Trends across sampled settings; the browser does not rerun FDTD |
All new video players start on a still image. Press play when you want motion; pause or use the timeline to compare frames. The captions describe the important features without requiring animation.
3. Measure the quantity you need
A bright field is not by itself a power, efficiency or gain measurement. Use flux monitors for reflected/transmitted power, the matching port calculator for S-parameters, and near-to-far-field analysis for radiation or scattering. Keep the reference run, normalization and measurement planes with the result.
Waves and materials
Follow a pulse through a dielectric interface or watch interference in a closed cavity. Both provide actual time-domain snapshots and downloadable arrays generated from their public source. They teach field behavior on one mesh, not numerical accuracy.
Then read the dielectric slab: see how the two interfaces create reflection and transmission, then run the flux-monitor tutorial. The linked legacy gallery records an older calculation; use its stated version when reading the comparison.
Try changing: slab permittivity or thickness, one at a time. Plot the full frequency response and compare with a lossless slab’s energy balance or its analytic reference, using the same model and reference planes.
Guided waves and filters
Compare the empty rectangular guide with the dielectric taper. The first introduces a guided mode; the second adds a material transition and a reflected-wave objective. The microstrip notch makes a compact next step: one length controls a resonant branch.
Try changing: the taper’s material profile or the stub length. Keep the port definition and normalization fixed so the curves answer the same question.
Radiation and scattering
The beam-steering film connects a dielectric cover to a far-field pattern. Then use the runnable antenna pattern example or scattering example from the source checkout.
Try changing: the source orientation before adding structural complexity. Check the collection surface, clearance and incident-reference subtraction. Directivity, realized gain and efficiency are different quantities.
Differentiable design
Read each optimization frame from left to right: parameter field, measured response, then sensitivity. A derivative refers to a particular parameterization and objective. The beam-steering film differentiates latent variables; the taper film displays section permittivity sensitivities.
Before using a gradient to support a design claim, check both finite-difference agreement and stability with a longer time record. See Gradient behavior and the inverse-design guide.
4. Make the result reproducible
Record the source revision, inputs, realized geometry and mesh, preflight output, measurement definition, and raw arrays. Put the plot, movie and response curve under the same model identity. If two panels came from different runs, say so.
The Examples hub leads to runnable scripts. The API reference describes the calls; Support Boundaries and Validation explain the scope of a result.