FEMOptions

class simpleEMS.fem_backend.FEMOptions(boundary: str = 'silver_muller', symmetry: tuple | None = None, fe_order: int = 1, air_pad_frac: float = 0.25, air_pad_mm: float | tuple | None = None, elems_per_wavelength: float = 16.0, mesh_freq: float | None = None, mesh_fine_scale: float = 1.0, min_layers: int = 3, num_solve_points: int = 10, max_solve_points: int | None = None, port_type: str = 'lumpedport', port_mode_modes: int = 6, port_mode_index: int = 0, port_mode_zc: float | None = None, port_mode_eps_eff: float | None = None, waveport_width_mm: float | None = None, waveport_height_mm: float | None = None, kappa_freq: float | None = None)

Bases: object

Solver and mesh options shared by every FEM entry point.

Bundles the settings into one object so they can be passed around together instead of as many separate arguments.

Parameters:

• boundary (str) – Outer boundary condition: "silver_muller" (default), "pml" or "pec". See SimParams for what each one is for.

• symmetry (tuple, optional) – Mirror-symmetry plane (axis, kind, at), where axis is "x", "y", or "z", kind is "pec" or "pmc", and at is the plane coordinate in metres (None for the structure centre). Only the half of the structure on one side of the plane is meshed. Default None (no symmetry).

• fe_order (int) – Element order, either 1 (default) or 2. Order 2 is more accurate and roughly three times as expensive to solve.

• air_pad_frac (float) – Air padding around the structure, as a fraction of the free-space wavelength at mesh_freq. Default 0.25. Ignored when air_pad_mm is set.

• air_pad_mm (float or tuple, optional) – Air padding around the structure in millimetres, used in place of air_pad_frac. Either one value for all six faces, three values [x, y, z] padding each axis symmetrically, or three [low, high] pairs padding every face on its own – so an antenna can carry deep air above the patch and little below the ground plane. Default None (pad by air_pad_frac).

• elems_per_wavelength (float) – Target number of mesh elements per wavelength, applied separately in each material. Default 16.0.

• mesh_freq (float, optional) – Frequency the mesh is sized at, in Hz. Element size and air padding are both derived from its wavelength, so this is the one number that sets how expensive the mesh is. Default None, which falls back to the top of the sweep; SimParams fills it with main_freq, so a wide plot range no longer refines the mesh.

• mesh_fine_scale (float) – Multiplier on the element size near conductors. Values above 1 coarsen the mesh there. Default 1.0.

• min_layers (int) – Number of element layers through the dielectric thickness. Default 3.

• num_solve_points (int) – Number of frequencies the sweep solves at, from which the full S-parameter curve is interpolated. Must be >= 4. Default 10.

• max_solve_points (int, optional) – Ceiling on the solve count when the interpolated curve breaks passivity and the sweep keeps solving to fix it. Must be >= num_solve_points. Default None, which allows twice num_solve_points. A passive response costs num_solve_points.

• port_mode_modes (int) – Number of eigenpairs each wave port’s mode solve computes. Raise it if a port reports that it found no guided mode. Default 6.

• port_type (str) – Which port the FEM backend makes of the ports the geometry already carries: "lumpedport" (default) drives one constant field direction across the port sheet, which is right for a gap feed; "waveport" solves the transverse mode of the port’s cross-section and drives that instead, which is what a transmission line needs. A coplanar waveguide port is always a wave port – its mode is odd, and a single constant vector excites the wrong one.

• port_mode_eps_eff (float, optional) – Effective permittivity naming which guided mode a wave port runs in: the mode whose own effective permittivity is closest to it is used. This is the robust way to pick a mode on a multi-conductor line, because it names the mode by a property of the line rather than by its position in a spectrum that changes with frequency and mesh density. Takes precedence over port_mode_index. Default None.

• port_mode_zc (float, optional) – Characteristic impedance in ohms to reference a wave port’s S-parameters to, overriding the one measured from the solved mode. The measured value is good to a few percent on a single-conductor line such as microstrip, but the power-voltage impedance of a multi-conductor mode depends on which path the voltage is integrated along, so on a coplanar waveguide it is better to state the impedance the line was designed for. Default None (use the measured value).

• port_mode_index (int) – Which guided mode a wave port runs in, counting from 0 for the one with the largest propagation constant. 0 (the default) is right for a single-conductor line such as microstrip. A cross-section with more than one conductor above the ground plane – conductor-backed coplanar waveguide is the common case – carries more than one quasi-TEM mode, and the one with the largest beta need not be the one the line is meant to run in. See fem_port_mode.

• waveport_width_mm (float, optional) – Width of each wave port’s cross-section in millimetres, centred on the line. Default None: 10 * w for a trace narrower than the substrate is thick, 5 * w otherwise, where w is the port’s width across the line.

• waveport_height_mm (float, optional) – Height of each wave port’s cross-section in millimetres, measured from the ground side of the substrate. Default None: six substrate thicknesses.

• kappa_freq (float, optional) – Frequency at which a CSXCAD material’s kappa was set, in Hz, which is where it has to be read back as a loss tangent. openEMS models dielectric loss as a conductivity fixed at one frequency – SimParams.substrate_kappa is tand*2*pi*main_freq*eps0*eps_r – so inverting it anywhere else scales the loss by the ratio of the two. Default None, which falls back to the sweep’s centre frequency.

Attributes Summary

air_pad_faces_mm	Return the air padding per face, or None to use air_pad_frac.
air_pad_frac
air_pad_mm
boundary
elems_per_wavelength
fe_order
kappa_freq
max_solve_points
mesh_fine_scale
mesh_freq
min_layers
num_solve_points
port_mode_eps_eff
port_mode_index
port_mode_modes
port_mode_zc
port_type
symmetry
waveport_height_mm
waveport_width_mm

Attributes Documentation

air_pad_faces_mm

Return the air padding per face, or None to use air_pad_frac.

Returns:

((x_lo, x_hi), (y_lo, y_hi), (z_lo, z_hi)) in millimetres, or None when no explicit padding is set.

Return type:

tuple[tuple[float, float], …] or None

air_pad_frac: float = 0.25

air_pad_mm: float | tuple | None = None

boundary: str = 'silver_muller'

elems_per_wavelength: float = 16.0

fe_order: int = 1

kappa_freq: float | None = None

max_solve_points: int | None = None

mesh_fine_scale: float = 1.0

mesh_freq: float | None = None

min_layers: int = 3

num_solve_points: int = 10

port_mode_eps_eff: float | None = None

port_mode_index: int = 0

port_mode_modes: int = 6

port_mode_zc: float | None = None

port_type: str = 'lumpedport'

symmetry: tuple | None = None

waveport_height_mm: float | None = None

waveport_width_mm: float | None = None