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Eigenmode filter#

This example shows how to use PyAEDT to automate the Eigenmode solver in HFSS. Eigenmode analysis can be applied to open radiating structures using an absorbing boundary condition. This type of analysis is useful for determining the resonant frequency of a geometry or an antenna, and it can be used to refine the mesh at the resonance, even when the resonant frequency of the antenna is not known.

The challenge posed by this method is to identify and filter the non-physical modes resulting from reflection from boundaries of the main domain. Because the Eigenmode solver sorts by frequency and does not filter on the quality factor, these virtual modes are present when the Eigenmode approach is applied to nominally open structures.

When looking for resonant modes over a wide frequency range for nominally enclosed structures, several iterations may be required because the minimum frequency is determined manually. Simulations re-run until the complete frequency range is covered and all important physical modes are calculated.

The following script finds the physical modes of a model in a wide frequency range by automating the solution setup. During each simulation, a user-defined number of modes is simulated, and the modes with a Q higher than a user-defined value are filtered. The next simulation automatically continues to find modes having a frequency higher than the last mode of the previous analysis. This continues until the maximum frequency in the desired range is achieved.

Keywords: HFSS, Eigenmode, resonance.

Perform imports and define constants#

Perform required imports.

[1]:

import os
import tempfile
import time

import ansys.aedt.core
from ansys.aedt.core.examples.downloads import download_file

Define constants.

[2]:

AEDT_VERSION = "2025.2"
NUM_CORES = 4
NG_MODE = False  # Open AEDT UI when it is launched.

Create temporary directory#

Create a temporary directory where downloaded data or dumped data can be stored. If you’d like to retrieve the project data for subsequent use, the temporary folder name is given by temp_folder.name.

[3]:

temp_folder = tempfile.TemporaryDirectory(suffix=".ansys")

Download 3D component#

Download the 3D component that is needed to run the example.

[4]:

project_path = download_file(
    "eigenmode", "emi_PCB_house.aedt", temp_folder.name
)

Launch AEDT#

[5]:

d = ansys.aedt.core.launch_desktop(
    AEDT_VERSION,
    non_graphical=NG_MODE,
    new_desktop=True,
)

PyAEDT INFO: Python version 3.10.11 (tags/v3.10.11:7d4cc5a, Apr  5 2023, 00:38:17) [MSC v.1929 64 bit (AMD64)].
PyAEDT INFO: PyAEDT version 0.24.dev0.
PyAEDT INFO: Initializing new Desktop session.
PyAEDT INFO: Log on console is enabled.
PyAEDT INFO: Log on file C:\Users\ansys\AppData\Local\Temp\pyaedt_ansys_a7250841-bd91-4c49-bb95-17d836793345.log is enabled.
PyAEDT INFO: Log on AEDT is disabled.
PyAEDT INFO: Starting new AEDT gRPC session.
PyAEDT INFO: AEDT installation Path C:\Program Files\ANSYS Inc\v252\AnsysEM
PyAEDT INFO: Client application successfully started.
PyAEDT INFO: New AEDT gRPC session session started on port 50051.
PyAEDT INFO: 2025.2 version started with process ID 1452.
PyAEDT WARNING: Service Pack is not detected. PyAEDT is currently connecting in Insecure Mode.
PyAEDT WARNING: Please download and install latest Service Pack to use connect to AEDT in Secure Mode.
PyAEDT INFO: Debug logger is disabled. PyAEDT methods will not be logged.

Launch HFSS#

Create an HFSS design.

[6]:

hfss = ansys.aedt.core.Hfss(
    version=AEDT_VERSION, project=project_path, non_graphical=NG_MODE
)

PyAEDT INFO: Parsing C:\Users\ansys\AppData\Local\Temp\tmpg1j758x2.ansys\eigenmode\emi_PCB_house.aedt.
PyAEDT INFO: Python version 3.10.11 (tags/v3.10.11:7d4cc5a, Apr  5 2023, 00:38:17) [MSC v.1929 64 bit (AMD64)].
PyAEDT INFO: PyAEDT version 0.24.dev0.
PyAEDT INFO: Returning found Desktop session with PID 1452!
PyAEDT INFO: File C:\Users\ansys\AppData\Local\Temp\tmpg1j758x2.ansys\eigenmode\emi_PCB_house.aedt correctly loaded. Elapsed time: 0m 0sec
PyAEDT INFO: Project emi_PCB_house has been opened.
PyAEDT INFO: Active Design set to with_chassis_em
PyAEDT INFO: Active Design set to with_chassis_em
PyAEDT INFO: Aedt Objects correctly read

Input parameters for Eigenmode solver#

The geometry and material should be already set. The analyses are generated by the code. The num_modes parameter is the number of modes during each analysis. The maximum allowed number is 20. Entering a number higher than 10 might result in a long simulation time as the Eigenmode solver must converge on modes. The fmin parameter is the lowest frequency of interest. The fmax parameter is the highest frequency of interest. The limit parameter determines which modes are ignored.

[7]:

num_modes = 6
fmin = 1
fmax = 2
next_fmin = fmin
setup_nr = 1
limit = 10
resonance = {}

Find modes#

The following cell defines a function that can be used to create and solve an Eigenmode setup. After solving the model, information about each mode is saved for subsequent processing.

[8]:

def find_resonance():
    # Setup creation
    next_min_freq = f"{next_fmin} GHz"
    setup_name = f"em_setup{setup_nr}"
    setup = hfss.create_setup(setup_name)
    setup.props["MinimumFrequency"] = next_min_freq
    setup.props["NumModes"] = num_modes
    setup.props["ConvergeOnRealFreq"] = True
    setup.props["MaximumPasses"] = 10
    setup.props["MinimumPasses"] = 3
    setup.props["MaxDeltaFreq"] = 5

    # Analyze the Eigenmode setup
    hfss.analyze_setup(setup_name, cores=NUM_CORES, use_auto_settings=True)

    # Get the Q and real frequency of each mode
    eigen_q_quantities = hfss.post.available_report_quantities(
        quantities_category="Eigen Q"
    )
    eigen_mode_quantities = hfss.post.available_report_quantities()
    data = {}
    for i, expression in enumerate(eigen_mode_quantities):
        eigen_q_value = hfss.post.get_solution_data(
            expressions=eigen_q_quantities[i],
            setup_sweep_name=f"{setup_name} : LastAdaptive",
            report_category="Eigenmode",
        )
        eigen_mode_value = hfss.post.get_solution_data(
            expressions=expression,
            setup_sweep_name=f"{setup_name} : LastAdaptive",
            report_category="Eigenmode",
        )
        data[i] = [eigen_q_value.data_real()[0], eigen_mode_value.data_real()[0]]

    print(data)
    return data

Automate Eigenmode solution#

Running the next cell calls the resonance function and saves only those modes with a Q higher than the defined limit. The find_resonance() function is called until the complete frequency range is covered. When the automation ends, the physical modes in the whole frequency range are reported.

[9]:

while next_fmin < fmax:
    output = find_resonance()
    next_fmin = output[len(output) - 1][1] / 1e9
    setup_nr += 1
    cont_res = len(resonance)
    for q in output:
        if output[q][0] > limit:
            resonance[cont_res] = output[q]
            cont_res += 1

resonance_frequencies = [f"{resonance[i][1] / 1e9:.5} GHz" for i in resonance]
print(str(resonance_frequencies))

PyAEDT INFO: Key Desktop/ActiveDSOConfigurations/HFSS correctly changed.
PyAEDT INFO: Solving design setup em_setup1
PyAEDT INFO: Design setup em_setup1 solved correctly in 0.0h 0.0m 50.0s
PyAEDT INFO: Key Desktop/ActiveDSOConfigurations/HFSS correctly changed.
PyAEDT INFO: PostProcessor class has been initialized! Elapsed time: 0m 0sec
PyAEDT INFO: PostProcessor class has been initialized! Elapsed time: 0m 0sec
PyAEDT INFO: Post class has been initialized! Elapsed time: 0m 0sec
PyAEDT INFO: Modeler class has been initialized! Elapsed time: 0m 1sec
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015854835510253906
Time to initialize solution data:0.015854835510253906
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.01591014862060547
Time to initialize solution data:0.01591014862060547
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015880584716796875
Time to initialize solution data:0.015880584716796875
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.016028404235839844
Time to initialize solution data:0.022781848907470703
PyAEDT INFO: Solution Data Correctly Loaded.

C:\actions-runner\_work\pyaedt-examples\pyaedt-examples\.venv\lib\site-packages\ansys\aedt\core\visualization\post\solution_data.py:729: UserWarning: Method `data_real` is deprecated. Use :func:`get_expression_data` property instead.
  warnings.warn("Method `data_real` is deprecated. Use :func:`get_expression_data` property instead.")

Time to initialize solution data:0.017969608306884766
Time to initialize solution data:0.017969608306884766
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.0
Time to initialize solution data:0.016084909439086914
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.01648712158203125
Time to initialize solution data:0.01648712158203125
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015647172927856445
Time to initialize solution data:0.015647172927856445
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.0
Time to initialize solution data:0.016057491302490234
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015756607055664062
Time to initialize solution data:0.015756607055664062
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015658140182495117
Time to initialize solution data:0.015658140182495117
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.0
Time to initialize solution data:0.015774250030517578
{0: [np.float64(103.06513375267946), np.float64(1355332420.34131)], 1: [np.float64(1.268215348193083), np.float64(1478857801.41881)], 2: [np.float64(0.8228778159574546), np.float64(1652467480.64678)], 3: [np.float64(0.6640591553693461), np.float64(1763970332.723)], 4: [np.float64(0.6766419577602678), np.float64(1765237546.4026)], 5: [np.float64(1.0259629202437963), np.float64(1821171387.40162)]}
PyAEDT INFO: Key Desktop/ActiveDSOConfigurations/HFSS correctly changed.
PyAEDT INFO: Solving design setup em_setup2
PyAEDT INFO: Design setup em_setup2 solved correctly in 0.0h 0.0m 53.0s
PyAEDT INFO: Key Desktop/ActiveDSOConfigurations/HFSS correctly changed.
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015831947326660156
Time to initialize solution data:0.015831947326660156
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015912532806396484
Time to initialize solution data:0.015912532806396484
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015300273895263672
Time to initialize solution data:0.015300273895263672
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.01571941375732422
Time to initialize solution data:0.020989418029785156
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015845060348510742
Time to initialize solution data:0.03153824806213379
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015745162963867188
Time to initialize solution data:0.015745162963867188
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015041351318359375
Time to initialize solution data:0.015041351318359375
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.0
Time to initialize solution data:0.01573348045349121
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.01613450050354004
Time to initialize solution data:0.01613450050354004
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.015880346298217773
Time to initialize solution data:0.015880346298217773
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.011756658554077148
Time to initialize solution data:0.011756658554077148
PyAEDT INFO: Solution Data Correctly Loaded.
Time to initialize solution data:0.010048627853393555
Time to initialize solution data:0.010048627853393555
{0: [np.float64(395.5699044962927), np.float64(1852676825.77992)], 1: [np.float64(0.7436448304796339), np.float64(2139379547.71637)], 2: [np.float64(456.2650870701165), np.float64(2261283109.83606)], 3: [np.float64(1.0908953023807333), np.float64(2347859232.9468)], 4: [np.float64(1.595326208776568), np.float64(2367242846.88747)], 5: [np.float64(1.8314043723259759), np.float64(2515365380.39913)]}
['1.3553 GHz', '1.8527 GHz', '2.2613 GHz']

Plot the model.

[10]:

hfss.modeler.fit_all()
hfss.plot(
    show=False,
    output_file=os.path.join(hfss.working_directory, "Image.jpg"),
    plot_air_objects=False,
)

PyAEDT INFO: Parsing design objects. This operation can take time
PyAEDT INFO: Refreshing bodies from Object Info
PyAEDT INFO: Bodies Info Refreshed Elapsed time: 0m 0sec
PyAEDT INFO: 3D Modeler objects parsed. Elapsed time: 0m 0sec

[10]:

Class: ansys.aedt.core.visualization.plot.pyvista.ModelPlotter

Release AEDT#

[11]:

hfss.save_project()
d.release_desktop()
# Wait 3 seconds to allow AEDT to shut down before cleaning the temporary directory.
time.sleep(3)

PyAEDT INFO: Project emi_PCB_house Saved correctly
PyAEDT INFO: Desktop has been released and closed.

Clean up#

All project files are saved in the folder temp_folder.name. If you’ve run this example as a Jupyter notebook, you can retrieve those project files. The following cell removes all temporary files, including the project folder.

[12]:

temp_folder.cleanup()

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