Antenna simulation workbench · openEMS FDTD

Design antennas. See the fields.

Draw an antenna, a microstrip circuit or an array in a ribbon-based 3D designer, or import a CST-compatible VBA macro. Fairbeam meshes it, runs the open-source openEMS solver on the CPU or the GPU, and shows the results next to the model: S-parameters with markers, radiation patterns, surface currents, sweeps, an optimizer, and exports for Touchstone, CST-compatible VBA macros and PCB fabrication.

Download Fairbeam Open the demo

Free desktop app for macOS (Apple silicon) and Windows. The browser demo is read-only and opens 14 example projects that were simulated beforehand.

How it works

From a model to fields, in one patch antenna

Model it
Draw it in the designer, where every length is an expression over named parameters, or import a CST-compatible VBA macro. The same model can also be one Python file with a build() that places metal, dielectrics and ports.
```
def build(p):
    sim = Simulation(1e9, 3e9)
    sim.metal("patch").AddBox(...)
    sim.dielectric("substrate", 3.38).AddBox(...)
    sim.lumped_port(1, 50, ...)
    return sim
```
Exact geometry
The viewer rebuilds every primitive exactly: a 32 × 40 mm patch on 1.524 mm of ε_r 3.38, the ground plane and a 50 Ω probe feed.
Meshed for FDTD
Fine cells at the patch edges and in the substrate, coarse ones in the air: 69 × 69 × 58 mesh lines, 263 k cells.
Excited, the currents flow
A Gaussian pulse at the feed rings the patch. This is the surface current openEMS recorded at resonance: strongest in the middle of the patch and falling to zero at the two radiating edges, as the TM₀₁₀ mode predicts.
It radiates
Near-to-far-field transform: 6.79 dBi broadside at 2.453 GHz, 96.5 % radiation efficiency. Radius and color both show directivity.
Checked, then exported
|S11| dips to −34.5 dB at 2.453 GHz, within 0.1 % of the converged mesh. Then everything goes out: a CST-compatible VBA macro, Touchstone, drawings, a report, Gerber files.

Arrays

Four patches, one beam you can steer

One patch becomes four
The same patch four times, half a wavelength apart (61.2 mm) on one 66 × 243.6 mm board, each with its own 50 Ω port. Fed in phase they reach 11.9 dBi broadside, about 5 dB above the single patch.
Steered by phase alone
A phase that falls by k·d·sin θ₀ from port to port turns the beam. openEMS ran once per port with the other three terminated in 50 Ω (four runs, 18 s on the GPU engine), so every angle here is the weighted sum of four embedded element patterns: coupling included, and each port's active reflection moves with the beam.
Your turn
Steer it. The app does the same for any amplitudes and phases, and exports the steered pattern.
Scan angle θ₀ +25°

Examples

Horns, helices, fractals and circuits

Pyramidal horn, WR-90
An optimum-gain horn fed by a TE₁₀ waveguide port, with PML boundaries: 15.5 dBi at 10 GHz and |S11| below −16 dB from 8 to 12 GHz.
Axial-mode helix
A Kraus helix, seven turns at 13° pitch over a square ground plane: right-hand circular, 11.6 dBi at 2.4 GHz, an axial ratio of 0.9 dB on boresight and the cross-polarized LHCP 26 dB lower.
Minkowski fractal patch
The fractal edge lengthens the current path: 30 × 30 mm of copper resonates at 2.324 GHz, below the 32 × 40 mm plain patch at 2.453 GHz on the same substrate, at the price of bandwidth (0.8 %).
Wilkinson divider
Three ports and one lumped 100 Ω resistor: an equal split with S21 = S31 = −3.09 dB. One openEMS run per driven port gives the full S-matrix.
Branch-line coupler
A 90° hybrid: −3.21 and −2.99 dB to the two outputs at 2.40 GHz, 90.0° apart, with the reciprocity and passivity of the four-port matrix checked.
Stepped-impedance low-pass
Alternating wide and narrow line sections: the −3 dB point lands at 2.356 GHz, 5.2 % below the ideal line cascade, because the steps themselves add capacitance.

Open all 14 examples in the demo

The pyramidal horn in Fairbeam: the flared horn on its WR-90 feed with the 3D directivity pattern above it, and |S11| from 8 to 12 GHz below it.

The axial-mode helix in Fairbeam: the wire helix over its ground plane inside the 3D directivity pattern, with polar cuts and the far-field summary below.

The designer

Model, simulate and read the results in one window

A ribbon on one row
Home, Modeling, Transform, Simulation, Optimize and Post-processing on one row. Draw bricks in 3D, extrude a picked face, combine shapes with booleans, and move, rotate, mirror or scale them in one Transform dialog (Ctrl+T).
Tree and properties
Components, materials, ports, lumped elements, mesh and results in a navigation tree with drag and drop. The panels collapse, Undo, Redo and a modeling history keep track of the edits, and a Python panel sits alongside.
Runs under the design
Every run is listed under Results with its S-parameters, far fields and surface currents. Picking one shows it in the 3D view: here the 4 × 1 array's pattern over its geometry.
Markers on every plot
Resonances and their bandwidth are marked, with a hover read-out, a two-marker bandwidth, your own markers and a table you can copy. Runs are compared by the parameters that differ.
One click out
Copy data or CSV in dB, phase, Re/Im or magnitude/phase, and Touchstone files. The ribbon adds a PDF report, an export package and the Python model, the header a CST-compatible VBA macro.

The Fairbeam designer with the Modeling ribbon tab: the navigation tree with components, materials and ports on the left, the branch-line coupler in the 3D view with its four 50 ohm ports, and the selected part's dimensions on the right.

The Fairbeam designer with the Post-processing ribbon tab: the 4 by 1 patch array with its 3D directivity pattern at 2.453 GHz, and the run listed under Results in the navigation tree.

Real outputs

The files, as they come out

A3 technical drawing of the rectangular patch antenna: top, front, side and isometric views with dimensions, a parameter table and a title block. — A3 drawing generated from the simulated geometry

Black-and-white publication chart of the patch antenna's |S11| in dB against frequency, with a dip near 2.45 GHz. — |S11| as a publication figure (8.8 cm)

Black-and-white publication chart of the Wilkinson divider's transmission: S21 and S31 near −3 dB and the isolation S23 against frequency. — Multi-port S-parameters, Wilkinson divider

Features

What Fairbeam does

Ribbon-based designer

A one-row ribbon, a collapsible navigation tree, properties and dock, and a Python side panel. Bricks, cylinders, spheres, cones, tori, wires, polygons and extrusions; draw bricks in 3D, extrude a picked face, booleans, one Transform dialog, shortcuts, Undo, Redo and Save As.
Import a VBA macro

Reads a CST-compatible VBA macro or history list: parameters, materials, shapes, booleans, transforms, ports, resistors, monitors, the band, the boundaries and manual mesh lines. An import report lists every command that was skipped or changed, with its line.
Parameters and checks

Every length and frequency is an expression over named parameters. Checks run as you edit and explain what they found; a design without an excited port, or one that cannot converge, is refused before any solver time is spent.
Start templates and examples

Start from a half-wave dipole, a quarter-wave monopole, an open-ended waveguide, a printed sleeve dipole or a two-port microstrip line, or pick an example from a searchable list, which now includes a 2-element collinear and a 5-element Yagi for 867 MHz.
Import PCB artwork

Home › Import PCB turns DXF, Gerber and Excellon files into a design; fairbeam import-pcb does the same from the command line.
Automatic meshing

Auto mode picks the mesh settings for each design, and every field can be overridden. Thin PCB copper is meshed as sheets, converted examples keep their own mesh lines, and the mesher lands within 0.1 % of converged hand meshes.
Mesh convergence

Simulation › Mesh convergence… runs the design at finer automatic meshes until the resonance, |S11| and D_max stop changing, and reports the density that converged. From the command line: fairbeam converge.
Run quality and one-click fixes

A run that did not converge, or whose numbers look suspicious, is flagged in the tree and on its results. Common design checks offer a fix in one click. Waveguide-port power is calibrated, so the pyramidal horn's efficiency reads about 99 %.
Parameter sweeps

Sequences, each over up to six parameters as ranges or value lists, checked before anything runs. The runs are queued, and every run of the sweep can be compared in one plot.
Goal-driven optimizer

Goals such as f₀, |S11| at a frequency, bandwidth, D_max or |S_ij| limits, over as many parameters as you vary. Secant, Nelder–Mead, Bayesian, CMA-ES, particle swarm, genetic and trust-region searches, with live progress; the best result is kept to open, apply or save.
Multi-port S-parameters

One openEMS run per driven port gives the full S-matrix of filters, dividers, couplers and arrays, with reciprocity and passivity checks, a picker for any S_ij, a Smith chart per port and Touchstone .sNp export.
Results with markers

Result tabs: S-parameters, impedance, VSWR, Smith chart, efficiency and patterns, with markers for resonances and bandwidth, hover read-outs and your own markers. Runs are compared by the parameters that differ; Copy data and CSV in dB, phase, Re/Im or magnitude/phase.
Result summaries and comparison

Headline numbers for each run in the tree and the Runs table, and Tables › Summary. A comparison table lists the parameters that differ between runs; copy it or save it as CSV.
2D and 3D field maps

The Field map tab shows E and H planes as heat maps with a read-out and the model's outline. Phase and Animate play a time-harmonic animation of the field, in 2D and in the 3D view.
Far field, currents, beams

3D patterns and polar cuts in directivity, gain, realized gain or RHCP/LHCP, with a card for D_max, gains, radiation, mismatch and total efficiency and the main lobe. Optionally, the radiation and total efficiency over the whole band, computed after the run (about 0.3 s for 21 frequencies on the patch; the solver time does not change). Animated surface currents, and array beams steered after the run.
GPU engines

Optional GPU builds of openEMS: Metal on Apple silicon and CUDA on NVIDIA cards under Windows. The patch antenna takes 1.6 s instead of 10.6 s on an M5 Pro, and 2.6 s instead of 53 s on a Ryzen 9 with an RTX 3060. When a GPU build is installed it is the default, and the CPU engine stays available.
VBA macro, drawings, fabrication

A CST-compatible VBA macro rebuilds the model in the target program, and Touchstone or CSV files can be compared against the run. Dimensioned drawings, publication figures, a PDF report, and Gerber, drill and DXF files (preview).
Desktop app

For macOS and Windows, in English or Turkish (General settings › Language, native menus included, with a Decimal separator setting), with Save As, and a question before closing unsaved work. First start installs Python and openEMS for your user account; projects live in Documents/Fairbeam, and updates are offered in the app.

Results

Measured, with the source of every number

Black-and-white polar chart of the patch antenna's directivity at 2.453 GHz in the xz and yz planes, with a broadside maximum of 6.79 dBi. — Directivity of the patch at 2.453 GHz in both principal planes, as exported for a paper (8.8 cm column width).

Validation

Against analytical results
Check	Fairbeam	Reference
Dipole D_max	2.13–2.15 dBi	2.11 dBi (theory)
Patch resonance	2.455 GHz	2.513 GHz (TL model), −2.3 %

Dipole: three lengths, 50 to 66 mm, end criterion −60 dB. Patch: converged mesh, against a transmission-line model. Details and commands in the validation notes of the repository.

Solver time in seconds

Apple M5 Pro: CPU engine with 4 threads and the optional Metal GPU engine. AMD Ryzen 9 7900X under Windows: CPU engine with 4 and all 24 threads, and the optional CUDA GPU engine on an NVIDIA RTX 3060
Model	Cells	Apple M5 Pro		Ryzen 9 7900X
Model	Cells	CPU	GPU	4 threads	24 threads	CUDA
Patch antenna, −60 dB	0.26 M	10.6	1.6	52.9	49.9	2.6
4 × 1 patch array (4 runs)	0.45 M	–	14.2	874	686	25.1
Sierpinski monopole	2.0 M	12.0	2.7	61.1	65.7	3.4

The same models give the same results on both platforms. Runs that stop at the same timestep agree within 0.1 dB in every S-parameter and 0.004 dB in D_max. The older Mac CPU runs checked the end criterion on a wall-clock schedule and stop at a different timestep, which moves only very deep |S11| nulls. The GPU engine is a separate openEMS fork (SeanMollet/openEMS, GPL-3.0, beta) built side by side; the CPU build stays the reference. The M5 Pro CPU time of the patch was re-measured on 2026-09-25 with the current model. Details and commands in the benchmark notes of the repository.

Circuits and arrays

Multi-port models on 0.813 mm, ε_r 3.38, GPU engine
Check	Fairbeam	Reference
Microstrip line Z₀	48.3 Ω	50.0 Ω (Hammerstad)
Wilkinson split S21 = S31	−3.09 dB	−3.01 dB (ideal)
Branch-line S21 / S31	−3.21 / −2.99 dB	−3.01 dB each
Low-pass −3 dB point	2.356 GHz	2.485 GHz (ideal)
4×1 array S11 / S22	−23.5 / −17.0 dB	4 GPU runs, 18 s

Wilkinson with the textbook 100 Ω resistor: output match and isolation stall at −18.4 and −22.0 dB, because the odd-mode impedance at the outputs is about 34 Ω. The lumped resistor itself is exact; the cause is still an open question. Branch-line at 2.40 GHz: 90.0° between the outputs. Low-pass: the step discontinuities pull the cutoff 5.2 % below the ideal line cascade, as expected for this filter type.

Optimizer

Measured runs of `fairbeam optimize` on the GPU engine
Task	Result	Cost
Dipole to f₀ = 2.40 GHz	2.4000 GHz	2 evaluations, 2.0 s
Wilkinson: all ports ≤ −20 dB, S23 ≤ −25 dB	82 Ω	3 evaluations, 7.6 s
Wilkinson: S23 ≤ −35 dB	73 Ω	4 evaluations, 3.6 s

The isolation resistor went from the textbook 100 Ω to 73 Ω in about 11 s; with all ports driven, 73 Ω gives S23 = −39.9 dB and every port matched below −24 dB.

Automatic mesh

Resonance with `auto_mesh()` against converged hand-tuned meshes
Model	Automatic	Converged
Dipole	2.4182 GHz	2.4198 GHz, −0.07 %
Patch antenna	2.4525 GHz	2.4550 GHz, −0.10 %

Try the viewer here

The read-only example viewer of the app, as on /app, with the 14 example projects; the designer and the solver need the desktop app. It loads three.js and one example project: about 1 MB, roughly 350 KB compressed.

Roadmap

Where Fairbeam is, and where it is going

75 features available, 0 in development and 0 planned, from the project's issues and pull requests. Updated 6 October 2026.

Available 75 items

In a release, or merged for the next one

Released in 0.7.0

Visual designer

Draw a parametric model, set up the simulation, run it and read the results in one window.

Designer
Tracked as #35
Status: v0.7.0
One-row ribbon

Home, Modeling, Transform, Simulation, Optimize and Post-processing on one row; the tree, dock and properties collapse, next to a Python side panel.

Designer
Tracked as #55 #77 #147
Status: v0.7.0
Draw in 3D and extrude faces

Draw a brick's base and then its height in the 3D view, or extrude a picked face into a new part.

Designer
Tracked as #144 #146
Status: v0.7.0
One Transform dialog

Translate, scale, rotate and mirror in one dialog (Ctrl+T), with a live preview.

Designer
Tracked as #56 #61 #143
Status: v0.7.0
Booleans, polygons included

Add, subtract and intersect shapes, including polygons, with a colour-coded preview.

Designer
Tracked as #80 #135 #156
Status: v0.7.0
Pick points, align and measure

Use vertices, edge midpoints and face centres for corners and origins; align parts and measure between points.

Designer
Tracked as #66 #135
Status: v0.7.0
Shortcuts and modeling history

A sheet of the keyboard shortcuts, and the session's modeling history.

Designer
Tracked as #81 #84 #133
Status: v0.7.0
A tree with context menus

Right-click menus on every node, show and hide, and drag and drop of parts into components.

Designer
Tracked as #44 #49 #79 #128 #132 #160
Status: v0.7.0
Parameters in the dock

A table of every parameter next to Checks, with CSV and JSON import and export.

Designer
Tracked as #53 #59 #148
Status: v0.7.0
Checks that explain themselves

Click a warning to see what was found, why it matters and how to fix it.

Designer
Tracked as #64 #70
Status: v0.7.0
Ports that find their ground

Add port here says what the port connects to and offers the other metals it found.

Designer
Tracked as #65 #67
Status: v0.7.0
Import VBA macro

A CST-compatible VBA macro or history list becomes a design, manual mesh lines included, with a report of what was skipped or changed.

Designer
Tracked as #168 #170
Status: v0.7.0
Save As

Save a design under a new name, in the app and from the File menu; Undo and Redo work from the menus too.

Designer
Tracked as #163 #167
Status: v0.7.0
Checks for misplaced metal

New warnings for metal that overhangs its substrate or floats off the structure.

Designer
Tracked as #177
Status: v0.7.0
Surface current in the ribbon

Simulation › Monitors has its own Surface current button, next to Far field.

Designer
Tracked as #176
Status: v0.7.0
Start templates

A half-wave dipole, a quarter-wave monopole, an open-ended waveguide, a printed sleeve dipole and a two-port microstrip line to start from.

Designer Status: v0.7.0
Import PCB artwork

DXF, Gerber and Excellon files become a design: Home › Import PCB, or fairbeam import-pcb.

Designer Status: v0.7.0
One-click check fixes

Common design checks offer a fix you can apply with one click.

Designer Status: v0.7.0
Automatic meshing

The FDTD mesh is built from the geometry, within 0.1 % of converged hand-tuned meshes.

Simulation Status: v0.7.0
Multi-port S-parameters

Full S-matrices of filters, dividers, couplers and arrays, with Touchstone export.

Simulation Status: v0.7.0
Sweeps and optimizer

Sweep one or two parameters, or let the optimizer tune them towards your goals.

Simulation Status: v0.7.0
Metal GPU engine

An optional Metal build of openEMS on Apple silicon: several times faster, same results.

Simulation Status: v0.7.0
CUDA GPU engine

An optional NVIDIA engine on Windows, in the Run panel: the patch in 2.6 s instead of 53 s.

Simulation
Tracked as #10 #14 #17 #19
Status: v0.7.0
Thin copper as sheets

Realistic 35 µm PCB copper is simulated as sheets, so runs keep a practical time step.

Simulation
Tracked as #38 #46
Status: v0.7.0
Convergence checks

A run that cannot converge is stopped before it starts, with the reason and a fix.

Simulation
Tracked as #39 #46
Status: v0.7.0
Thin copper in exported models

A design exported to Python builds the same copper sheets as the designer's own run.

Simulation
Tracked as #63
Status: v0.7.0
Auto mesh mode

The mesh settings are picked for each design, and any field can be overridden.

Simulation
Tracked as #145
Status: v0.7.0
Parameter sweeps

Sequences over up to six parameters each, checked before they run, queued, and compared run by run.

Simulation
Tracked as #151 #155
Status: v0.7.0
A stronger optimizer

Live progress, the best result kept, any number of parameters, and Bayesian, CMA-ES, particle-swarm, genetic and trust-region searches.

Simulation
Tracked as #150
Status: v0.7.0
No run without a port

A design with no port, or no excited port, is refused with a check instead of failing.

Simulation
Tracked as #166
Status: v0.7.0
Examples keep their mesh

An example opened as a new project keeps its exact mesh lines, so it gives the same results.

Simulation
Tracked as #164 #165 #169
Status: v0.7.0
Optimizer skips misplaced metal

Candidates the design checks refuse are skipped without a simulation and shown as Skipped.

Simulation
Tracked as #177
Status: v0.7.0
GPU build by default

When the GPU build of openEMS is installed, the app starts with it and offers both engines; a general setting switches it.

Simulation
Tracked as #176
Status: v0.7.0
Mesh convergence

Simulation › Mesh convergence… refines the automatic mesh until the results stop changing; fairbeam converge does the same from the command line.

Simulation Status: v0.7.0
Run-quality warnings

A run that did not converge, or whose numbers look suspicious, is flagged in the tree and on its results.

Simulation Status: v0.7.0
Far field, currents and beam steering

3D patterns, gain and efficiency, surface currents, and array beams steered after the run.

Results Status: v0.7.0
Drawings, reports and fabrication files

Dimensioned drawings, publication figures, a PDF report, and Gerber and drill files.

Results Status: v0.7.0
VBA macro export

A CST-compatible VBA macro rebuilds the model in the target program.

Results Status: v0.7.0
Solver times on reference machines

See how long the same model takes on an Apple M5 Pro and a Ryzen 9 with CUDA.

Results
Tracked as #30 #31
Status: v0.7.0
Every run kept

Each run keeps its own result, and Results opens the newest run instead of the preview.

Results
Tracked as #40 #42
Status: v0.7.0
Results in the design tree

Each run appears under its design, with its S-parameters, far fields, currents and log.

Results
Tracked as #52 #58
Status: v0.7.0
Post-processing tab

Selecting a result opens its plot, compare and export tools in the ribbon.

Results
Tracked as #55
Status: v0.7.0
Markers

Resonances, a two-marker bandwidth, hover read-outs and your own markers, with a table.

Results
Tracked as #154 #158
Status: v0.7.0
Compare runs

Runs side by side, with the parameters that differ marked; copy or save several runs at once.

Results
Tracked as #127 #131 #136
Status: v0.7.0
Complex formats and Touchstone

Copy data and CSV in dB, phase, Re/Im or magnitude/phase, and Touchstone export.

Results
Tracked as #100 #113 #152
Status: v0.7.0
Result tabs

Results open as tabs in the main area, with an A/B/C table of the runs.

Results
Tracked as #172
Status: v0.7.0
Animated surface currents

Phase-resolved surface currents play as a smooth animation in the 3D view.

Results
Tracked as #174
Status: v0.7.0
Gain and polarization in patterns

3D patterns and cuts in directivity, gain, realized gain, or RHCP and LHCP for circular polarization.

Results
Tracked as #180
Status: v0.7.0
Far-field card in the 3D view

Dmax, gain, realized gain, radiation, mismatch and total efficiency and the main lobe, next to the pattern.

Results
Tracked as #180
Status: v0.7.0
Efficiency result

1D Results › Efficiency: mismatch efficiency over the band, with the radiation and total efficiency, per driven port.

Results
Tracked as #180
Status: v0.7.0
Efficiency over the band

Optional radiation and total efficiency across the band from Simulation › Monitors › Efficiency, computed after the run without changing the solver time.

Results
Tracked as #179
Status: v0.7.0
Result summaries

Headline numbers for each run in the tree and the Runs table, Tables › Summary, and a comparison table of the parameters that differ, to copy or save as CSV.

Results Status: v0.7.0
2D field maps with phase and animation

The Field map tab shows E and H planes as heat maps; Phase and Animate play a time-harmonic animation, in 2D and 3D.

Results Status: v0.7.0
Desktop app for macOS and Windows

Installs its own Python and openEMS on first start, for your account, without admin rights.

Desktop app
Tracked as #1 #2
Status: v0.7.0
Updates in the app

New versions are offered in the app, checked against their signature, and install themselves.

Desktop app Status: v0.7.0
Sturdier on Windows

Proxies are honoured, interrupted downloads resume, and the server always stops with the app.

Desktop app
Tracked as #4 #7 #8 #15 #18 #25 #27 #29
Status: v0.7.0
Clean updates and uninstall

On Windows, an update replaces the old files and uninstalling removes the whole folder.

Desktop app
Tracked as #36
Status: v0.7.0
GPU preference on Windows

“Prefer the GPU build” on the setup screen now works on Windows too.

Desktop app
Tracked as #20 #37
Status: v0.7.0
Sharp on scaled displays

Layouts fit 125 % and 150 % Windows scaling and follow each monitor's pixel density.

Desktop app
Tracked as #48
Status: v0.7.0
Start, Design and Examples

Examples open read-only with their results; Open as new project turns one into a design.

Desktop app
Tracked as #51 #76 #153 #157
Status: v0.7.0
Native menus and settings

File, Edit, View, Window and Help menus, an About dialog, general settings and native Save As for exports.

Desktop app
Tracked as #139 #159
Status: v0.7.0
No lost work

Closing a project, the window or the app asks to save, discard or cancel when there are unsaved changes.

Desktop app
Tracked as #41 #43 #99 #118
Status: v0.7.0
A window that fits

The window opens at a size that fits the screen, or maximized on smaller screens.

Desktop app
Tracked as #176
Status: v0.7.0
Turkish and English interface

General settings › Language, native menus included, and a Decimal separator setting.

Desktop app Status: v0.7.0
Searchable example picker

Find an example by name, with new 867 MHz collinear and Yagi examples.

Desktop app Status: v0.7.0
Validated results

Checked against analytical results.

Performance & quality Status: v0.7.0
Benchmarks on Mac and Windows

All 14 examples timed on both platforms, with matching results.

Performance & quality
Tracked as #9 #13
Status: v0.7.0
Honest efficiency figures

Efficiencies above 100 % are flagged, and runs report the end criterion they reached.

Performance & quality
Tracked as #11
Status: v0.7.0
A faster, steadier designer

The 3D view reuses its geometry, and edits survive slow loads, saves and previews.

Performance & quality
Tracked as #24 #28
Status: v0.7.0
Keyboard access

Designer commands stay visible and every control can be reached from the keyboard.

Performance & quality
Tracked as #26
Status: v0.7.0
Projects open reliably

A preview arriving mid-load can no longer replace the project you asked for.

Performance & quality
Tracked as #62
Status: v0.7.0
Faster meshing of detailed designs

Automatic meshing of polygon designs and arrays runs 4 to 64 times faster.

Performance & quality
Tracked as #71
Status: v0.7.0
A quicker designer

The Start screen opens in half the time, and checks and saves answer sooner.

Performance & quality
Tracked as #72 #73 #74
Status: v0.7.0
Large designs stay responsive

Big polygon designs edit, preview and check faster, with identical results.

Performance & quality
Tracked as #104 #105 #137 #138
Status: v0.7.0
Horn efficiency

Waveguide-port power is calibrated, so the pyramidal horn's radiation efficiency reads about 99 %.

Performance & quality
Tracked as #12 #162
Status: v0.7.0

In development 0 items

Open pull requests and work under way

Nothing here right now.

Planned 0 items

Approved, not started yet

Nothing here right now.

Download

From download to a first simulation

Download the installer
It installs for your user account, without admin rights.

macOSApple silicon · macOS 27+Download .dmg ↓ Windows0.7.0 · x64 · Windows 10/11Download .exe ↓
First start sets up the runtime
Python 3.13, the Python packages and openEMS, each pinned by SHA-256 and installed once into your user folder: 120–155 MB, about 20 s on a fast connection. An existing openEMS installation works too.
Examples in your Documents
The workspace is Documents/Fairbeam: the example projects, their models and templates are copied there, and your designs sit next to them. Examples open read-only; Open as new project turns one into a design you can edit.
Press Run
The Run dialog offers the CPU engine and, when one is installed, the GPU engine; the dock shows live progress, the field energy and the time left. The patch antenna takes 10.6 s on four CPU threads of an Apple M5 Pro, or 1.6 s with the optional Metal GPU engine, and about 53 s on four threads of a Ryzen 9 7900X under Windows.

Fairbeam

Available installers

fairbeam_0.7.0_macos-arm64.dmg11.7 MB
fairbeam_0.7.0_windows-x64-setup.exe8.6 MB
SHA256SUMS.txtchecksums

Per-user install · no admin rights · updates are offered in the app

Install the runtime

uv 0.12.19✓
Python 3.13✓
openEMS 0.37.0-rc3✓
numpy · h5py · matplotlib · CSXCAD✓
import CSXCAD, openEMS, fairbeam✓

Every download is checked against its SHA-256 · nothing is installed system-wide

Documents/Fairbeam

projects/
patch-antenna.json
patch-array-4x1.json
wilkinson-divider.json · …
models/
patch_antenna.py · …
templates/ · jobs/

Run · patch-antenna

openEMS · CPU · 4 threads · 263 k cells0.0 s

mesh 69 × 69 × 58 lines
field energy −60 dB: converged
near-to-far field at 2.453 GHz: D_max 6.79 dBi
|S11| −34.5 dB at 2.453 GHz · project written

Status

What to expect

Development preview: The designer, the solver pipeline and the results work end to end. The file formats are versioned (fairbeam.design/1 for designs, fairbeam.project/1 for results); breaking changes bump the version. The source repository is not public yet.
VBA macro export not yet validated: The exported CST-compatible VBA macro and the macro import are not validated for every command or physical port formulation; the macro import reports the commands that it skips or changes. Check an exported model in the target program before relying on it.
Fabrication files not yet validated: The Gerber, drill and DXF files are parsed back and checked against the geometry to 1 µm, but have not been opened in a Gerber viewer or sent to a fab. The simulation uses zero-thickness copper; clearances and footprints are yours to check.
Wilkinson output match: open question: With the textbook 100 Ω resistor the divider's output match and isolation fall short of theory. The resistor model is exact, so the cause is either the layout or the staircase mesh at the resistor node; a finer mesh at the resistor node will tell.
Unsigned installers, macOS 27+: The macOS app is signed and notarized by Apple. The Windows installer is not signed yet, so Windows SmartScreen warns. The macOS openEMS build needs macOS 27 or newer on Apple silicon. Linux has no installer yet; the Python package works with any openEMS installation whose Python bindings import.
Licenses: Fairbeam is GPL-3.0-or-later; openEMS is GPL-3.0-or-later and CSXCAD LGPL-3.0-or-later. The complete source of every released version is available on request: open an issue in fairbeam-releases. Project files are plain data produced by your own models.

Download

Download Fairbeam

Free desktop app. On first start it installs its runtime once for your user account: Python, the Python packages and openEMS. That is about 120–155 MB to download and 20–30 s on a fast connection, with no admin rights and nothing installed system-wide. You can also point it at an existing openEMS installation. Windows includes CPU support and offers optional NVIDIA GPU setup in Settings; no separate app installer is needed.

macOS 0.7.0 · Apple silicon · macOS 27+ · .dmg · 11.7 MB Download ↓ Windows 0.7.0 · x64 · Windows 10/11 · installer · 8.6 MB Download ↓

macOS 0.7.0: macOS 27 or newer; the app is signed and notarized. Windows 0.7.0: Windows 10/11, per-user install; SmartScreen warns because the installer has no Authenticode certificate (More info → Run anyway). Checksums are in SHA256SUMS.txt. Every version is on the releases page. Later versions are offered in the app.

Linux (preview): no installer yet. With repository access, scripts/install-openems-linux.sh builds openEMS (CPU) in your user folder and scripts/run-linux.sh opens Fairbeam in your browser. Tested on Debian 13 x86_64; see docs/LINUX.md.

New here? Read the getting-started guide: install, a first design, the run and its results in about five minutes.

# From source (repository access): macOS, Homebrew, Xcode CLT, Python 3.10+, Node.js 20+
# 1. Build openEMS + CSXCAD into ~/opt/openEMS and install Fairbeam into its venv (5–10 min)
scripts/install-openems-macos.sh

# 2. Run a model: writes public/projects/<slug>.json
~/opt/openEMS/venv/bin/fairbeam run python/models/patch_antenna.py

# 3. Start the viewer on http://127.0.0.1:5310, and the run server
npm install
npm run dev
npm run serve

# Linux (preview, CPU): build openEMS into your user folder, then open Fairbeam in the browser
scripts/install-openems-linux.sh
scripts/run-linux.sh

# the desktop app from source
npm run desktop:build

Design antennas. See the fields.

From a model to fields, in one patch antenna

Model it

Exact geometry

Meshed for FDTD

Excited, the currents flow

It radiates

Checked, then exported

Four patches, one beam you can steer

One patch becomes four

Steered by phase alone

Your turn

Horns, helices, fractals and circuits

Pyramidal horn, WR-90

Axial-mode helix

Minkowski fractal patch

Wilkinson divider

Branch-line coupler

Stepped-impedance low-pass

Model, simulate and read the results in one window

A ribbon on one row

Tree and properties

Runs under the design

Markers on every plot

One click out

The files, as they come out

What Fairbeam does

Ribbon-based designer

Import a VBA macro

Parameters and checks

Start templates and examples

Import PCB artwork

Automatic meshing

Mesh convergence

Run quality and one-click fixes

Parameter sweeps

Goal-driven optimizer

Multi-port S-parameters

Results with markers

Result summaries and comparison

2D and 3D field maps

Far field, currents, beams

GPU engines

VBA macro, drawings, fabrication

Desktop app

Measured, with the source of every number

Validation

Solver time in seconds

Circuits and arrays

Optimizer

Automatic mesh

Try the viewer here

Where Fairbeam is, and where it is going

Visual designer

One-row ribbon

Draw in 3D and extrude faces

One Transform dialog

Booleans, polygons included

Pick points, align and measure

Shortcuts and modeling history

A tree with context menus

Parameters in the dock

Checks that explain themselves

Ports that find their ground

Import VBA macro

Save As

Checks for misplaced metal

Surface current in the ribbon

Start templates

Import PCB artwork

One-click check fixes

Automatic meshing

Multi-port S-parameters

Sweeps and optimizer

Metal GPU engine

CUDA GPU engine

Thin copper as sheets

Convergence checks

Thin copper in exported models

Auto mesh mode