Sources and Boundary Condition Problem Handling
This page contains a list of the most important warning and error messages
in the context of source, boundary and material modeling together with
a detailed explanation of the meaning and proposal for handling and resolution.
Contents
Excitation sources
Waveguide ports
Multipin ports
Floquet ports
Source configuration
Materials
Boundaries
Lumped Network Elements
Excitation sources
Waveguide ports
Port number "xxx"
is completely filled with metal. Maybe the background material is defined
as PEC?
All degrees of freedom inside the port plane lie
inside metal material, so that no mode pattern can be calculated. Please
check whether the background material is defined as PEC or the port is
located inside a metal object.
Some higher order
propagating modes at port "xxx" are not considered in time domain
calculation. This possibly leads to an inaccurate energy balance. Consider
to increase the number of modes or decrease the upper frequency limit.
In case of a multi-conductor port usually TEM or
QTEM modes are of interest. Depending on the dimension of the waveguide
port and the upper limit of the global frequency range, there might also
occur higher order propagating modes in addition. Usually this is not
intended and these modes can be stopped from propagating by lowering the
upper frequency limit. In principle it is also possible to reduce the
port size, but this has to be done very carefully in order to still sufficiently
cover the mode patterns of the relevant TEM and QTEM modes. In case that
the higher order propagating modes are intended as e.g. box modes, the
number of modes should be increased to consider these modes correctly
for simulation.
Some higher order evanescent
modes at port "xxx" are not sufficiently decaying concerning
the structure dimension. This possibly leads to an inaccurate energy balance.
Consider to increase the number of modes or decrease the upper frequency
limit.
In case of a multi-conductor port usually TEM or
QTEM modes are of interest. Depending on the dimension of the waveguide
port and the upper limit of the global frequency range, there might also
occur higher order evanescent modes. Usually these modes have no important
influence on the simulation, because they are decaying over a very small
distance. However, in case that their damping constant is small their
influence cannot be neglected anymore. By lowering the upper frequency
limit these modes will be damped more intensively. In principle it is
also possible to reduce the port size, but this has to be done very carefully
in order to still sufficiently cover the mode patterns of the relevant
TEM and QTEM modes. In case that the higher order evanescent modes are
intended as e.g. box modes, the number of modes should be increased to
consider these modes correctly for simulation.
At least one propagating
mode at port "xxx" is not considered in the time domain calculation!
(At least one mode shares the same beta with considered mode(s) ->
degeneration) It might be better to increase the number of modes at port
"xxx".
"nnn" degenerated mode(s) at port "xxx" is/are not
considered in time domain calculation! It might be better to increase
the number of modes at port "xxx".
This warning is shown when some propagating TE or
TM modes are not considered in the simulation. Usually this is not intended
and the modes could be taken into account by increasing the number of
modes. In case of missing degenerated modes (sharing the same propagation
constant) this is even more important to provide an accurate simulation
result.
The first mode at inhomogeneous
port "xxx" is hybrid. This could lead to an inaccurate energy
balance. Please check your structure.
Hybrid modes exist at inhomogeneous port "xxx". This could lead
to an inaccurate energy balance. Please check your structure.
When the calculated field pattern at the port is
a six-component mode, which can not be decomposed into two or more degenerated
modes, this warning will be generated. Typically this is caused by incorrect
structure modeling such as a microstrip transmission line where the ground
plane does not intersect the port. Please check your port setup.
There exist non-(Q)TEM
modes for the inhomogeneous port "xxx". This may lead to an
inaccurate energy balance. Consider to decrease the upper frequency limit.
Although expected for a multiconductor port, one
or more modes could not be classified as (Q)TEM at some frequency point.
This usually happens at higher frequencies when longitudinal field components
become stronger. The modes are classified as TE/TM or hybrid in this case.
Consider to decrease the upper frequency limit.
The inhomogeneous
port "xxx" shows a strong dispersive behavior. Please increase
the number of modes.
At inhomogeneous ports it is necessary to track
the mode pattern over frequency in order to provide correct scattering
parameters. However, this is only possible if the mode patterns vary not
too much between the lower and upper frequency limit. Furthermore, mode
propagation constants might interchange over frequency such that the corresponding
mode cannot be found anymore. In this case it might be necessary to increase
the number of modes.
Inhomogeneous port accuracy
enhancement: Port "xxx" shows a strong dispersive behavior which
could lead to inaccurate S-parameter results. Please decrease the upper
frequency limit.
The inhomogeneous port accuracy enhancement can
compensate errors introduced by frequency dependent mode patterns. However,
this is only possible if the mode patterns vary not too much between the
lower and upper frequency limit. If this warning is issued please consider
decreasing the upper frequency limit or splitting the frequency range
in higher and lower bands.
Multipin ports
Multipin port "xxx"
is strongly inhomogeneous, i.e. the corresponding modes represent combinations
of field patterns with different propagation properties. This may lead
to an inaccurate energy balance.
At inhomogeneous multipin ports QTEM modes are combined
to satisfy the specified potential set definition. If the propagation
constants of the modes differ too much they cannot be considered as degenerate
anymore and they should not be combined.
Some (Q)TEM modes were not
found on port "xxx". Consider to increase the mode calculation
frequency.
To create a multpin port mode that satisfies the
specified potential settings it is necessary to linearly combine the existing
degenerated TEM or QTEM modes. If the mode calculation frequency is very
low not all modes may be available. Consider increasing the mode calculation
frequency in the specials
dialog of the time domain solver or adjusting the global frequency
range.
Some (Q)TEM modes are
not considered at port "xxx". This may lead to an inaccurate
energy balance.
It is important that the number of defined potential
sets equals the number of degenerated QTEM or TEM modes in the waveguide.
If not a large part of the field may propagate in the unconsidered mode
patterns. The waveguide port boundary still treats these fields internally
but they will not contribute to the scattering matrix and may therefore
lead to an inaccurate energy balance.
The multipin potential
settings on port "xxx" result in linearly dependent field patterns.
Please note that the mode fields will be orthogonalized to ensure stability.
The defined potential sets should result in linear
independent field patterns, e.g. the “even” and “odd” modes in a three
conductor port. Otherwise the fields at the port cannot properly be decomposed
into mode amplitudes. Please check whether the potential set definition
is meaningful or consider treating the port as single-ended.
Multipin port
"xxx" calculates a zero mode pattern. Maybe your structure shows
some unwanted electric cavities. Changing boundaries from electric to
magnetic possibly solves this problem.
This warning is shown when a multipin port area
has some decoupled mode regions, so called cavities. This might happen
either by an incorrect port setup or by electric transversal port boundary
conditions which creates cavities between themselves and the outer port
conductor. In the latter case changing the boundary conditions to magnetic
can remove these unwanted cavities.
Floquet ports
At least one
propagating Floquet mode is not considered at port "xxx". Please
increase the number of modes at this port.
It is important to consider all propagating modes
in the simulation, since those parts of the fields attributed to unconsidered
modes will be reflected at the Floquet port boundary. This usually may
lead to inaccurate S-parameters. Please include all propagting modes by
increasing the number of modes considered at the Floquet port in the Settings
for Floquet Boundary dialog.
Materials
The material
"xxx" has a very high conductivity for the given mesh. It may
be better to use a lossy metal type for this material.
The material "xxx" has a very low conductivity for the lossy
metal model. It may be better to use a normal type for this material.
In order to simulate conductive material, the mesh
has to be refined such, that the field variation (e.g. skin depth) is
sufficiently discretized. This might lead to an extremely fine mesh representation
for highly conductive materials. For these kind of materials the "lossy
metal" model should be applied, which takes into account the skin
effect without refining the mesh. However, if the skin depth is larger
than the metal thickness and a radiation effect through the metal is of
importance, the “lossy metal” model cannot be used anymore and type "normal"
should be selected. This is also true for materials with very low conductivity
where the "normal" material type offers a more accurate simulation
result than the "lossy metal" surface model.
The two warning messages indicate which material
type selection should be preferred. Please find a more detailed description
on these and other material types on the Material
Overview page.
Boundaries
Lumped Network Elements
At least one end point of "xxx" is not connected to any good
conductor.
At least one end point of the following discrete ports or lumped elements
is not connected to any good conductor: ...
Some discrete ports or lumped network elements were
found which are not connected to any good conductor, for instance "floating"
some distance away from a conductor due to modelling tolerances. Especially
at low frequencies, results then can differ from what is expected, since
the connection to the remaining three-dimensional representation of the
circuit is uncertain. Please zoom in to inspect the connectivity of the
network elements, and create them again if necessary (preferably pick
a part of the conductors the network element should be connected to).
The check for floating elements considers the end
points of edge lumped network elements. This also the case for the face
ports and face lumped network elements: they have an alternative edge
lumped network element associated with them which is used by solvers that
do not support the face type lumped network elements. For the sake of
simplicity and performance of the connectivity check, these associated
edges will be used for the face lumped network elements. For each of their
end points, the check tries to find a conductor body that contains the
point. PEC and lossy metal solids are considered as good conductors, as
well as normal materials with a conductivity higher than 1000 S/m.
Face lumped elements are only supported over rectangular, cylinder-barrel
or radial surfaces.
The error message is displayed if the shape of the
face lumped network elements is not supported or not recognized, for instance
due to modelling accuracy. Rectangular, cylinder-barrel and radial lumped
network elements are supported. They are illustrated by the first three
lumped network elements in the picture below. Please delete and re-create
the lumped network elements so that their shape is either rectangular,
cylinder-barrel, radial like, or use straight edge lumped network elements.
from left to right: a rectangular discrete port, a cylinder-barrel lumped
network element, a radial discrete port, a lumped network element of different
shape
The dimensions of the discrete face port "xxx" are not consistent:
The length is "yyy" in the model and "zzz" in the mesh.
The width is "yyy" in the model and "zzz" in the mesh.
The inner radius is "yyy" in the model and "zzz" in the mesh.
The general purpose frequency domain solver with tetrahedral mesh
verifies the dimensions of the discrete face ports to check if the mesh representation of
the discrete face port agrees with how the source was modeled.
In order to apply one of the face port definitions shown in the
picture above, the characteristic dimensions must be known to the solver and the mesh
needs to be consistent with that data.
One reason for this error message is an overlap of the discrete face
port with solids made of PEC or lossy metal material. They effectively reduce the area of
the discrete face port.
Another case where this error message is shown may occur if symmetry conditions are present
and the face port touches the symmetry plane without being symmetric to the symmetry condition.
Please enlarge the discrete face port in that case.
The two examples below show the unsupported case at the top and the recommended solution at the
bottom:
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