Openems

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An MCP server for designing antennas and electromagnetic structures using openEMS FDTD simulation. Provides analytical design calculators that work immediately, plus openEMS script generation for full-wave simulation.

Part of the engineering toolkit

This repo is part of eng-mcp-suite, an MCP-driven engineering toolkit for RF / EMC / PCB / signal-integrity / lab-test workflows.

Related tools in the toolkit:

Tool	When to reach for it
lineforge	2D quasi-TEM closed-form for transmission lines (microstrip, stripline, CPWG, differential, three-conductor). Use this when you need impedance fast and the geometry is 2D.
mcp-nec2-antenna	Wire-antenna method-of-moments (dipole / Yagi / vertical / loop / inverted-V). Use this when you have a wire-antenna geometry and don't need the 3D-field detail of FDTD.
mcp-pcb-emcopilot	PCB layout review (decoupling, return paths, plane resonances, DDR/PCIe/USB SI). Often pairs with mcp-openems for full-wave validation of a flagged region.

When to use mcp-openems specifically: full-wave 3D FDTD validation, broadband S-parameters, near/far-field characterization, antenna geometries with 3D features (horns, helices), or when closed-form is running out of accuracy.

Features

Antenna Design Tools

• openems_create_patch - Microstrip patch antenna (WiFi, GPS, satellite)
• openems_create_dipole - Half-wave dipole antenna
• openems_create_monopole - Quarter-wave monopole over ground plane
• openems_create_horn - Pyramidal horn antenna for specified gain
• openems_create_helix - Axial-mode helix for circular polarization

Simulation & Export

• openems_generate_script - Generate complete OpenEMS Python simulation script
• openems_check_installation - Check if OpenEMS is available

Design Management

• openems_list_designs - List all designs in session
• openems_get_design - Get full design details with geometry
• openems_list_antenna_types - Reference for antenna types and applications

Installation

1. Clone and install

git clone https://github.com/RFingAdam/mcp-openems.git
cd mcp-openems
uv pip install -e .

2. (Optional) Install OpenEMS for simulation

The MCP works without OpenEMS: the design tools calculate dimensions analytically. Full FDTD simulation needs the CSXCAD and openEMS Python bindings.

These are not on PyPI. pip install CSXCAD openEMS does not work. They are compiled extensions built from source against the openEMS C++ install:

git clone --recursive https://github.com/thliebig/openEMS-Project.git
cd openEMS-Project
./update_openEMS.sh ~/opt/openEMS          # builds the C++ libraries
source .venv/bin/activate                  # the venv you installed this MCP into
./scripts/build_python.sh --cpp-install-dir ~/opt/openEMS

Two things that will bite you, both of which broke this repo in 2026-08:

• The bindings are ABI-pinned to one Python minor version. A cpython-314 extension is invisible to a 3.12 interpreter, and vice versa. If you recreate the venv on a different Python, rebuild the bindings too.
• They link against system HDF5, VTK and boost. A distro upgrade that bumps those sonames breaks every .so here with libhdf5_serial.so.NNN: cannot open shared object file. Rebuild against the new libraries; build_python.sh --cpp-install-dir rebuilds only the Python layer, which is enough when the C++ install is already current.

Run openems_check_installation to see which of these you are hitting: it reports the real import error and the interpreter in use.

3. Add to your MCP client

Claude Code:

claude mcp add openems -- uv run --directory /path/to/mcp-openems mcp-openems

Config file format:

{
  "command": "uv",
  "args": ["run", "--directory", "/path/to/mcp-openems", "mcp-openems"]
}

Usage Examples

Design a WiFi patch antenna

Design a 2.4 GHz patch antenna on FR-4 substrate (er=4.4, 1.6mm thick)

The AI will:

1. Use openems_create_patch to calculate dimensions
2. Return patch length, width, feed position
3. Provide estimated directivity and impedance

Design a satellite uplink antenna

I need a circularly polarized antenna for 5.8 GHz with about 12 dBi gain

The AI will use openems_create_helix for CP requirements.

Generate simulation script

Generate an OpenEMS script for this antenna so I can run a full simulation

The AI will use openems_generate_script to create a complete Python script.

Compare antenna types

What antenna types are available? I need something for a handheld radio at 440 MHz

The AI will use openems_list_antenna_types and recommend appropriate options.

Tool Reference

Design Output Format

Each design tool returns:

• design_id: UUID for referencing the design
• dimensions: Calculated physical dimensions in mm
• calculated: Derived parameters (impedance, gain estimates)
• geometry: OpenEMS-compatible geometry specification

Example Output

{
  "success": true,
  "design_id": "550e8400-e29b-41d4-a716-446655440000",
  "design": {
    "name": "2.4 GHz Patch",
    "type": "patch",
    "frequency_ghz": 2.4,
    "dimensions": {
      "patch_length_mm": 28.85,
      "patch_width_mm": 37.24,
      "feed_inset_mm": 8.92,
      "ground_plane_mm": 94.48
    },
    "calculated": {
      "effective_er": 3.33,
      "estimated_directivity_dbi": 7.2
    }
  }
}

Generated Script

The openems_generate_script tool creates a complete Python script that:

1. Sets up the FDTD simulation
2. Creates geometry from the design
3. Adds mesh with appropriate resolution
4. Runs the simulation
5. Extracts S-parameters and plots results

Antenna Design Formulas

Antenna	Method	Key Formula
Patch	Transmission Line Model	L = c/(2f√εeff) - 2ΔL
Dipole	Classical	L = 0.95 × λ/2
Monopole	Image Theory	H = 0.95 × λ/4
Horn	Aperture Theory	G = 4πAe/λ²
Helix	Kraus Model	C ≈ λ, S = C tan(α)

Without OpenEMS

Even without OpenEMS installed, this MCP provides:

• Analytical dimension calculations
• Geometry specifications for manual modeling
• Reference impedance and gain estimates
• OpenEMS script generation for later use

With OpenEMS

With OpenEMS installed, you can run the generated scripts to:

• Perform full-wave FDTD simulation
• Get accurate S-parameters and input impedance
• Calculate radiation patterns and gain
• Visualize fields in ParaView

Supported Frequencies

The design tools work across the RF spectrum:

• HF (3-30 MHz): Dipole, monopole
• VHF (30-300 MHz): All types
• UHF (300 MHz-3 GHz): All types
• Microwave (3-30 GHz): Patch, horn, helix
• mmWave (30-300 GHz): Patch, horn (with appropriate substrate)

License

AGPL-3.0-or-later. Relicensed from Apache-2.0 in v0.2.0 to align with the eng-mcp-suite toolkit-wide AGPL move. The underlying openEMS engine remains GPL-3.0; this wrapper is AGPL-3.0-or-later and invokes the engine at runtime without redistribution.

Trademarks and brand assets

This project is not affiliated with, endorsed by, or sponsored by the openEMS project. "openEMS" is used here only to identify the software this project interoperates with.

The project name and the logo files in this repository are not part of the licensed work. The licence above grants no permission to use them, except as needed to describe the origin of the work.

Author

Adam Engelbrecht - @RFingAdam