rfx

rfx is a 3-D finite-difference time-domain (FDTD) electromagnetic simulator built in JAX. These docs focus on maintained user workflows with explicit support boundaries.

Start with the uniform Cartesian Yee FDTD solver. The table summarizes the documented workflows and their limits:

If a capability is not listed here or on the Support Boundaries page, treat it as outside the documented public support scope until that page lists it.

pip install rfx-fdtd

GPU support depends on your JAX/CUDA environment:

pip install "jax[cuda12]" rfx-fdtd

from rfx import Box, GaussianPulse, Simulation

sim = Simulation(
    freq_max=5e9,
    domain=(0.14, 0.06, 0.05),
    dx=2e-3,
    boundary="cpml",
    cpml_layers=8,
)
sim.add_material("slab", eps_r=2.2, sigma=0.01)
sim.add(Box((0.07, 0.018, 0.018), (0.09, 0.042, 0.032)), material="slab")
sim.add_source(
    (0.03, 0.03, 0.025),
    "ez",
    waveform=GaussianPulse(f0=3e9, bandwidth=0.8),
    amplitude_kind="current",   # amperes; required from 1.9, the default from 2.0
)
sim.add_probe((0.11, 0.03, 0.025), "ez")

preflight = sim.preflight()
print(preflight.format())
preflight.raise_for_failure()

result = sim.run(n_steps=1200)
print(result.time_series.shape)

This records a dielectric pulse response without making a resonance or Q claim. Resolve any preflight warning introduced by model changes. Use the First Patch tutorial for a patch model that passes preflight and the checks required before reporting resonance or Q.

• Installation — Python/JAX install, GPU notes, dev setup
• Quick Start — first simulation with the current high-level API
• Your First Patch Antenna — build a model, run a short check, and learn what is required before reporting RF results
• Studio, CLI, and MCP Experiments — local UI, versioned CPU runs, replay, and MCP approvals

• Simulation API — Simulation, Result, auto_configure, ports, NTFF, and design helpers
• Materials & Geometry — library materials, Debye/Lorentz, CSG shapes, PCB stackup
• Sources & Ports — point sources, lumped/wire ports, microstrip-line ports, waveguide ports, and coaxial-line reflection for exactly one face="top" port within its stated limits
• Probes & S-Parameters — DFT probes, S-matrix helpers, Harminv, de-embedding, exports
• Memory Reduction — reduce FDTD/AD memory while preserving validation boundaries
• ADI Solver (experimental) — unconditionally stable ADI-FDTD for stiff meshes, its timestep-vs-accuracy trade, and what is validated
• Waveguide Ports — rectangular waveguide modal workflows

• Cross-Validation & Accuracy — which page carries which kind of validation evidence
• Benchmarks — quantitative benchmark summary
• Convergence Study — mesh refinement workflow
• Far-Field & RCS — NTFF radiation patterns and scattering workflows
• Visualization & Analysis — plotting, exports, post-processing

• Autodiff and Adjoint Background — Meep-informed gradient concepts for microwave engineers
• Inverse Design — autodiff-driven optimization with documented proxy objectives
• Gradient Behavior — where gradients are usually well behaved vs noisy
• Parametric Sweeps — sequential sweep and jax.vmap design-space exploration
• Patch Antenna Design — rectangular patch workflow

• Examples — recommended public runnable paths
• Validation — public support and validation overview
• Gallery — examples with their RF evidence and limits stated on each page
• API — curated public API contract