# Lossy Metal Medium

LossyMetalMedium represents a lossy metal that can be modeled with a surface impedance boundary condition (SIBC).

This object corresponds to tidy3d.rf.LossyMetalMedium (opens new window).

# Name

name: Optional unique name for the medium.

# Type

type: Medium model used by this material entry.

  • Options: LossyMetalMedium

# Color

color: Display color used for the medium in the GUI.

  • Type: color
  • Default: automatically assigned by the GUI

# General Properties

conductivity: Electric conductivity used to model metal loss.

  • Type: float number
  • Unit: S/um
  • Constraint: greater than or equal to 0
  • Required field

set_from_global_frequency: Toggle whether the frequency range is set from the Global Settings frequency range.

  • Options:
    • True: Use the global frequency range and disable manual frequency range inputs.
    • False: Manually set frequency_range.

frequency_range: Frequency range where the medium model is valid.

  • Type: two float numbers
  • Unit: Hz, kHz, MHz, GHz, THz, or other available frequency unit
  • Required field

roughness: Optional surface roughness model that applies a frequency-dependent scaling factor to the surface impedance.

  • Options:
    • None: Do not apply a surface roughness correction.
    • Hammerstad: Use the modified Hammerstad surface roughness model.
    • Huray: Use the Huray surface roughness model.
  • Default: None

# Fitting Parameters

max_num_poles: Maximal number of poles in complex-conjugate pole residue model for fitting surface impedance.

  • Type: integer
  • Constraint: greater than 0
  • Default: 5

tolerance_rms: Root-mean-square tolerance used for fitting the surface impedance model.

  • Type: float number
  • Constraint: greater than 0
  • Default: 0.001

frequency_sampling_points: Number of frequency sampling points used for the fitting process.

  • Type: integer
  • Constraint: greater than 0
  • Default: 20

log_sampling: Toggle whether the fitting frequencies are sampled on a logarithmic scale.

  • Options: True/False
  • Default: True

# Advanced

thickness: Optional conductor thickness.

When the conductor thickness is not much greater than the skin depth, a one-dimensional transmission line model is applied to compute the surface impedance of the thin conductor.

  • Type: float number
  • Unit: m, mm (default in the RF GUI), um, or other available length unit
  • Constraint: greater than 0
  • Default: None

allow_gain: Toggle whether the medium is allowed to be active.

  • Options: True/False
  • Default: False

NOTE

SIBC is most accurate when the skin depth is much smaller than the structure feature size. If this condition is not satisfied, use a regular medium or choose an appropriate lossy metal subpixel averaging method.