QPDK Coupled Resonator — Driven Simulation¶
This notebook builds a compact coupled resonator from QPDK cells, converts etch layers to conductor geometry, and runs a Palace driven simulation to extract S-parameters around the resonance near 7.5 GHz.
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 microstrip transmission line with via ports.
Requirements:
- IHP PDK:
uv pip install qpdk - GDSFactory+ account for cloud simulation
import gdsfactory as gf
from qpdk import PDK, cells
from qpdk.cells.airbridge import cpw_with_airbridges
from qpdk.tech import LAYER, route_bundle_sbend_cpw
PDK.activate()
@gf.cell
def resonator_compact(coupling_gap: float = 20.0) -> gf.Component:
"""Compact coupled resonator with S-bend CPW routes."""
c = gf.Component()
res = c << cells.resonator_coupled(
coupling_straight_length=300, coupling_gap=coupling_gap
)
res.movex(-res.size_info.width / 4)
left = c << cells.straight()
right = c << cells.straight()
w = res.size_info.width + 100
left.move((-w, 0))
right.move((w, 0))
route_bundle_sbend_cpw(
c,
[left["o2"], right["o1"]],
[res["coupling_o1"], res["coupling_o2"]],
cross_section=cpw_with_airbridges(
airbridge_spacing=250.0, airbridge_padding=20.0
),
)
c.kdb_cell.shapes(LAYER.SIM_AREA).insert(c.bbox().enlarged(0, 100))
c.add_port(name="o1", port=left["o1"])
c.add_port(name="o2", port=right["o2"])
return c
component = resonator_compact(coupling_gap=15.0)
_c = component.copy()
_c.draw_ports()
_c
/home/runner/work/gsim/gsim/.venv/lib/python3.12/site-packages/gdsfactory/components/bends/bend_s.py:66: UserWarning: {'width': 10.0} ignored for cross_section 'coplanar_waveguide'
xs = gf.get_cross_section(cross_section, width=width)
Convert QPDK etch layers to conductor geometry¶
import warnings
import klayout.db as kdb
from gsim.common.polygon_utils import decimate
from qpdk.tech import LAYER as QPDK_LAYER
sim_area_layer = (QPDK_LAYER.SIM_AREA[0], QPDK_LAYER.SIM_AREA[1])
etch_layer = (QPDK_LAYER.M1_ETCH[0], QPDK_LAYER.M1_ETCH[1])
CPW_LAYERS = {"SUBSTRATE": (1, 0), "SUPERCONDUCTOR": (2, 0), "VACUUM": (3, 0)}
layout = component.kdb_cell.layout()
sim_region = kdb.Region(
component.kdb_cell.begin_shapes_rec(layout.layer(*sim_area_layer))
)
etch_region = kdb.Region(component.kdb_cell.begin_shapes_rec(layout.layer(*etch_layer)))
etch_polys = decimate(list(etch_region.each()))
etch_region = kdb.Region()
for poly in etch_polys:
etch_region.insert(poly)
if sim_region.is_empty():
warnings.warn("No polygons found on SIM_AREA", stacklevel=2)
if etch_region.is_empty():
warnings.warn("No polygons found on M1_ETCH", stacklevel=2)
conductor_region = sim_region - etch_region
etched = gf.Component("etched_component")
el = etched.kdb_cell.layout()
for name, region in [
("SUPERCONDUCTOR", conductor_region),
("SUBSTRATE", sim_region),
("VACUUM", sim_region),
]:
idx = el.layer(*CPW_LAYERS[name])
etched.kdb_cell.shapes(idx).insert(region)
for port in component.ports:
etched.add_port(name=port.name, port=port)
etched
Configure simulation¶
from gsim.common.stack import Layer, LayerStack
from gsim.common.stack.materials import MATERIALS_DB
from gsim.palace import DrivenSim
# Build a CPW stack matching the etched component layers
substrate_thickness = 500
vacuum_thickness = 500
stack = LayerStack(pdk_name="qpdk")
stack.layers["SUBSTRATE"] = Layer(
name="SUBSTRATE",
gds_layer=(1, 0),
zmin=0.0,
zmax=substrate_thickness,
thickness=substrate_thickness,
material="sapphire",
layer_type="dielectric",
)
stack.layers["SUPERCONDUCTOR"] = Layer(
name="SUPERCONDUCTOR",
gds_layer=(2, 0),
zmin=substrate_thickness,
zmax=substrate_thickness,
thickness=0,
material="aluminum",
layer_type="conductor",
)
stack.layers["VACUUM"] = Layer(
name="VACUUM",
gds_layer=(3, 0),
zmin=substrate_thickness,
zmax=substrate_thickness + vacuum_thickness,
thickness=vacuum_thickness,
material="vacuum",
layer_type="dielectric",
)
stack.dielectrics = [
{
"name": "substrate",
"zmin": 0.0,
"zmax": substrate_thickness,
"material": "sapphire",
},
{
"name": "vacuum",
"zmin": substrate_thickness,
"zmax": substrate_thickness + vacuum_thickness,
"material": "vacuum",
},
]
stack.materials = {
"sapphire": MATERIALS_DB["sapphire"].to_dict(),
"aluminum": MATERIALS_DB["aluminum"].to_dict(),
"vacuum": MATERIALS_DB["vacuum"].to_dict(),
}
sim = DrivenSim()
sim.set_geometry(etched)
sim.set_stack(stack)
sim.add_cpw_port(
"o1", layer="SUPERCONDUCTOR", s_width=10.0, gap_width=6.0, length=5.0, offset=2.5
)
sim.add_cpw_port(
"o2", layer="SUPERCONDUCTOR", s_width=10.0, gap_width=6.0, length=5.0, offset=2.5
)
sim.set_driven(fmin=7.75e9, fmax=7.8e9, num_points=100)
sim.set_output_dir("./sim_qpdk_resonator")
sim.mesh(preset="graded", margin=0)
sim.plot_mesh(
show_groups=["superconductor", "P", "sapphire", "vacuum"], interactive=False
)
palace-7ec67df2 completed 6m 04s
Extracting results.tar.gz...
Downloaded 6 files to /home/runner/work/gsim/gsim/nbs/sim-data-palace-7ec67df2
import matplotlib.pyplot as plt
import pandas as pd
df = pd.read_csv(results["port-S.csv"])
df.columns = df.columns.str.strip()
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 — QPDK Coupled Resonator")
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()
