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 - design tools calculate dimensions analytically
# For full FDTD simulation, install OpenEMS:
pip install CSXCAD openEMS

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.

Author

Adam Engelbrecht - @RFingAdam