Running Palace Simulations

Contents

Running Palace Simulations#

Palace is an open-source 3D electromagnetic simulator supporting eigenmode, driven (S-parameter), and electrostatic simulations. This notebook demonstrates using the gsim.palace API to run a driven simulation on a CPW (coplanar waveguide) structure.

Requirements:

IHP PDK: uv pip install ihp-gdsfactory
GDSFactory Simulation SDK: uv pip install gsim
GDSFactory+ account for cloud simulation

Load a pcell from IHP PDK#

import gdsfactory as gf

from ihp import LAYER, PDK

PDK.activate()


@gf.cell
def gsg_electrode(
    length: float = 300,
    s_width: float = 20,
    g_width: float = 40,
    gap_width: float = 15,
    layer=LAYER.TopMetal2drawing,
) -> gf.Component:
    """
    Create a GSG (Ground-Signal-Ground) electrode.

    Args:
        length: horizontal length of the electrodes
        s_width: width of the signal (center) electrode
        g_width: width of the ground electrodes
        gap_width: gap between signal and ground electrodes
        layer: layer for the metal
    """
    c = gf.Component()

    # Top ground electrode
    r1 = c << gf.c.rectangle((length, g_width), centered=True, layer=layer)
    r1.move((0, (g_width + s_width) / 2 + gap_width))

    # Center signal electrode
    _r2 = c << gf.c.rectangle((length, s_width), centered=True, layer=layer)

    # Bottom ground electrode
    r3 = c << gf.c.rectangle((length, g_width), centered=True, layer=layer)
    r3.move((0, -(g_width + s_width) / 2 - gap_width))

    # Add ports at the gaps
    c.add_port(
        name="P1",
        center=(-length / 2, -(s_width + gap_width) / 2),
        width=gap_width,
        orientation=0,
        port_type="electrical",
        layer=layer,
    )

    c.add_port(
        name="P2",
        center=(-length / 2, (s_width + gap_width) / 2),
        width=gap_width,
        orientation=0,
        port_type="electrical",
        layer=layer,
    )

    c.add_port(
        name="P3",
        center=(length / 2, (s_width + gap_width) / 2),
        width=gap_width,
        orientation=180,
        port_type="electrical",
        layer=layer,
    )

    c.add_port(
        name="P4",
        center=(length / 2, -(s_width + gap_width) / 2),
        width=gap_width,
        orientation=180,
        port_type="electrical",
        layer=layer,
    )

    return c


c = gsg_electrode()
cc = c.copy()
cc.draw_ports()
cc

2026-02-22 16:32:53.417 | WARNING  | doroutes.pcells:<module>:25 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.420 | WARNING  | doroutes.pcells:<module>:48 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.423 | WARNING  | doroutes.pcells:<module>:109 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.425 | WARNING  | doroutes.pcells:<module>:146 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.426 | WARNING  | doroutes.pcells:<module>:161 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.428 | WARNING  | doroutes.pcells:<module>:201 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.430 | WARNING  | doroutes.pcells:<module>:235 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.432 | WARNING  | doroutes.pcells:<module>:260 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

2026-02-22 16:32:53.434 | WARNING  | doroutes.pcells:<module>:285 - Cannot determine output type ((D)KCell type)from annotation <class 'kfactory.kcell.DKCell'>. Trying to continue but likely this will fail.

_images/46c73d915e2fe63570863074e6982aa1f909ff8dffced3e0f1adf050c0597f43.png

Configure and run simulation with DrivenSim#

from gsim.palace import DrivenSim

# Create simulation object
sim = DrivenSim()

# Set output directory
sim.set_output_dir("./palace-sim-cpw")

# Set the component geometry
sim.set_geometry(c)

# Configure layer stack from active PDK
sim.set_stack(substrate_thickness=2.0, air_above=300.0)

# Configure left CPW port (P1 lower, P2 upper)
sim.add_cpw_port("P2", "P1", layer="topmetal2", length=5.0)

# Configure right CPW port (P4 lower, P3 upper)
sim.add_cpw_port("P3", "P4", layer="topmetal2", length=5.0)

# Configure driven simulation (frequency sweep for S-parameters)
sim.set_driven(fmin=1e9, fmax=100e9, num_points=40)

# Validate configuration
print(sim.validate_config())

Validation: PASSED

# Generate mesh (presets: "coarse", "default", "fine")
sim.mesh(preset="default")

Warning : 5 ill-shaped tets are still in the mesh
Warning : ------------------------------
Warning : Mesh generation error summary
Warning :     1 warning
Warning :     0 errors
Warning : Check the full log for details
Warning : ------------------------------

Mesh Summary
========================================
Dimensions: 500.0 x 330.0 x 418.3 µm
Nodes:      4,049
Elements:   31,726
Tetrahedra: 23,222
Edge length: 0.40 - 323.88 µm
Quality:    0.481 (min: 0.001)
SICN:       0.535 (all valid)
----------------------------------------
Volumes (4):
  - air [1]
  - passive [2]
  - SiO2 [3]
  - airbox [4]
Surfaces (7):
  - topmetal2_xy [5]
  - topmetal2_z [6]
  - P1_E0 [7]
  - P1_E1 [8]
  - P2_E0 [9]
  - P2_E1 [10]
  - Absorbing_boundary [11]
----------------------------------------
Mesh:   palace-sim-cpw/palace.msh

# Static PNG
sim.plot_mesh(show_groups=["metal", "P"], interactive=False)

# Interactive
# sim.plot_mesh(show_groups=["metal", "P"], interactive=True)

2026-02-22 16:32:57.024 (   2.653s) [    7FF783335B80]vtkXOpenGLRenderWindow.:1460  WARN| bad X server connection. DISPLAY=
2026-02-22 16:32:57.025 (   2.653s) [    7FF783335B80]vtkOpenGLRenderWindow.c:645   WARN| Failed to load EGL! Please install the EGL library from your distribution's package manager.
2026-02-22 16:32:59.072 (   4.700s) [    7FF783335B80]vtkOpenGLRenderWindow.c:645   WARN| Failed to load EGL! Please install the EGL library from your distribution's package manager.

_images/a8abf2386862d7f2da809d4793f68094c8f7958e1f457ebe6dd315e765ae0110.png

Run simulation on cloud#

# Generate Palace config file
sim.write_config()

PosixPath('palace-sim-cpw/config.json')

# Run simulation on GDSFactory+ cloud
results = sim.simulate()

Uploading simulation...

done

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Extracting results.tar.gz...
Downloaded 6 files to /home/runner/work/IHP/IHP/docs/sim-data-palace-e3d5c4b8/results/output/palace

import matplotlib.pyplot as plt
import pandas as pd

df = pd.read_csv(results["port-S.csv"])
df.columns = df.columns.str.strip()  # Remove whitespace from column names

freq = df["f (GHz)"]

fig, (ax1, ax2) = plt.subplots(2, 1, figsize=(6, 6))

# Magnitude plot
ax1.plot(freq, df["|S[1][1]| (dB)"], marker=".", label="S11")
ax1.plot(freq, df["|S[2][1]| (dB)"], marker=".", label="S21")
ax1.set_xlabel("Frequency (GHz)")
ax1.set_ylabel("Magnitude (dB)")
ax1.set_title("S-Parameters")
ax1.legend()
ax1.grid(True)

# Phase plot
ax2.plot(freq, df["arg(S[1][1]) (deg.)"], marker=".", label="S11")
ax2.plot(freq, df["arg(S[2][1]) (deg.)"], marker=".", label="S21")
ax2.set_xlabel("Frequency (GHz)")
ax2.set_ylabel("Phase (deg)")
ax2.legend()
ax2.grid(True)

plt.tight_layout()

_images/d040541bd4904d6a064885548e58add82e4b9c02317139d6dde090b08ab25b09.png