Tabulated Surface Impedance
Materials New/EditNew MaterialType: Surface imp. (table) Properties
Edit Object Properties (
Materials:material1PropertiesType: Surface imp. (table) Properties)
This dialog allows to define a frequency dependent,
isotropic surface impedance model. The data is provided in tabulated form,
with the resistance and reactance given for discrete frequencies. This
option is available for the transient solver and the frequency domain
solver with tetrahedral mesh. See the material overview for details.
Surface impedance
Fitting scheme: For the Tabulated Surface impedance the
only available dispersion model is
General Nth order, due to its wide range of application
and generality. For
detailed information about this scheme see the Material Overview.
Frequency/Resistance/Reactance/Weight:
In
this list box, the specific resistance and reactance can be defined by
setting several values at different frequency points. Moreover
to each frequency a weight (value greater than/equal to 0.0) is assigned
in order to direct the interpolation algorithm and to enforce a reduced
error in correspondence of the given frequency point.
An important observation
is that in correspondence of General
Nth order fitting, due to specific algorithm requirements,
the weight behaves as a switch between considered and ignored samples.
A weight less then 1.0 forces the interpolation algorithm to ignore the
given sample, whereas a weight greater/equal 1.0 to consider the sample
itself.
Max order: This control, available in case
of General Nth order fitting, enables the user to specify the maximum allowed model
order (total number of real and complex poles each counted with the corresponding
multiplicity). The search of the best fitting model is then stopped to
the given maximum order even if the error convergence criterion is not
fulfilled.
It
should always taken into account that increasing the model order may improve
the quality of the fitting but at the same time the simulation complexity
in terms of memory and computational time.
Used order: Displays the effective model order provided
by the interpolation algorithm. The model order corresponds to the total
number of real and complex poles each counted with the corresponding multiplicity
(in formulas, Order = num Real Pole + 2 x num Complex Poles).
Error limit: This
control, available in case of General
Nth order fitting, enables the user to specify
the error stopping criterion during the search of the best fitting model.
The error should be interpreted as the maximum relative error computed
in correspondence of each given frequency point between the (complex)
impedance value and the fitting curve. A useful interpretation of the Error limit
is as "error" or "inaccuracy" during measurement of
the real material properties.
Error: Displays the obtained fitting error. The error should
be interpreted as the maximum relative error computed in correspondence
of each given frequency point between the (complex) impedance value and
the fitting curve.
Details...: Opens a
dialog displaying information about the fitted model, in terms of position
of zeroes and poles in the complex plane for the impedance transfer function, see also Material
Overview (HF).
The representation
is subdivided in constant, linear, first and second order contributions.
The constant term
corresponds to a frequency independent contribution, whereas the linear
term is related physically to the contribution of an inductance (purely
reactive element).
The first order
contribution corresponds to a real pole, whose frequency is computed and
shown.
The second order
contribution may derive from a couple of real poles or from a couple of
complex conjugate poles. In the former case the frequency of the poles
is computed. In the latter case the resonance frequency of the pole together
with the quality factor (Q) is shown.
The description
of these parameters and the mathematical formulas that relate the first
and second order polynomial coefficients to the physical interpretation
of poles, zeroes and resonance frequencies may be found in Material
Overview (HF).
Use data in frequency range: This control, available in case of General Nth order
fitting, allows the fitting algorithm to use only the frequency data points
that lie within the "frequency range settings" defined by the
user (see also Frequency
Range Settings). Activating this check box enables an accurate data
fitting of the material resonances which occur in the simulation bandwidth
of interest using possibly a reduced number of poles and zeroes with respect
to the complete data fitting. And this, in turn, translates into benefits
for the simulation complexity in terms of memory and computational time.
Transparent sheets: Sheets may be either transparent, with
the electric field being the same on both sides of the sheet, or opaque,
which means that there will not be any direct coupling between front-
and back-side of a sheet.
Load
File...: Opens a file selector dialog to specify a ASCII file containing
point coordinates.
The file is formatted
in lines which specify the frequency points. Each line has four entries
specifying respectively frequency, value of real and imaginary part of
the impedance (i.e. resistance and reactance)
and weight. The weight field may be skipped and is assumed by default
equal to 1.0.
Moreover
it is possible to set a default frequency unit scale which is applied
to all loaded data samples.
Delete: Press this button to delete all selected rows in
the impedance versus frequency list box.
Clear List: Press this button to delete all entries of
the impedance versus frequency list box.
OK
Accepts the
input and closes the dialog.
Cancel
Closes this
dialog box without performing any further action.
Apply
To apply the settings and show
the fitted curve.
Help
Shows this
help text.
See also
Material Parameters: Material
Overview (HF)
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