ems

A pure Rust FDTD (finite-difference time-domain) electromagnetic field solver, intended as a replacement for openEMS.

• Clean-room implementation: no openEMS or CSXCAD code was consulted. See CLEANROOM.md. MIT licensed.
• Models come from csx, the companion CSXCAD-compatible geometry and material crate. ems adds the solver: mesh compilation, time stepping, boundaries, sources, probes, ports, and post-processing.
• Goal: run existing openEMS XML models unchanged.
• Edition 2024, MSRV 1.95.

Status: early development (milestone 1 mostly done). The API will still change. See docs/DESIGN.md for the architecture and roadmap.

Quick start

Build a model with csx, describe the solver settings with ems::Fdtd, run it, and analyse the port:

use csx::primitives::BoxShape;
use csx::{ContinuousStructure, Primitive, Property};
use ems::prelude::*;

let mut model = ContinuousStructure::new();
model.grid.delta_unit = 1e-3; // drawing unit: mm
for a in 0..3 {
    model.grid.set_lines(a, (0..=40).map(f64::from))?;
}
let sub = model.add_property(Property::material("sub", csx::Material::new(4.3, 0.0)));
model.add_primitive(sub, Primitive::new(BoxShape::new([0., 0., 0.], [40., 40., 2.])))?;
let port = LumpedPort::new(1, 50.0, [20., 20., 0.], [20., 20., 2.], Axis::Z)
    .excite(1.0)
    .add_to(&mut model)?; // writes LumpedElement + Excitation + probes into the model

let fdtd = Fdtd::new()
    .waveform(Waveform::gaussian(2e9, 1e9))
    .boundaries(Boundaries::all(Boundary::pml(8)))
    .end_criteria(EndCriteria::energy_decay_db(-40.0));
let mut sim = Simulation::new(&model, &fdtd)?;
for w in sim.warnings() {
    eprintln!("warning: {w}"); // includes the solver-aware mesh checks
}
let res = sim.run()?;
let z_in = port.analyze(&res, &[1e9, 2e9, 3e9])?.z_in();

Run an existing openEMS XML file (Simulation::from_xml in the API):

cargo run --release --example run_xml -- model.xml [--threads N] [--out DIR]

It prints warnings, progress and the outcome, and writes every probe as DIR/<name>.csv and every dump as .vtr files. More examples: cavity, microstrip, patch_antenna, dipole (cargo run --release --example <name>).

Status

Features

Documentation

License

MIT. See LICENSE.