Electromagnetic simulation
is used heavily in the design of many
electromagnetic systems and components.
An example of this is sensors for ADAS
And, when designing these sensors
the excitation of the signal
is critical to the accuracy of the design
for collision avoidance.
Ansys HFSS is often used during the
design stage
and is an integral part of the design process
And, in order to calculate the fields and
S-parameter matrix that's associated
with the model geometry
HFSS needs 'Ports'.
The excitation or ports are where the
signal goes in to a model geometry.
And, they have a direct
impact on the quality of the results
that HFSS yields for a given model.
The proper creation and use
of excitation is important to obtain the most
accurate HFSS results.
And, in this video module
I'm going to describe the available port types
inside of HFSS Ansys Electronics Desktop
There are several port types
several different types of excitations in HFSS
We have Wave ports, Lumped ports,
Floquet ports, Incident fields,
Current sources, Voltage sources,
Magnetic bias sources, Circuit ports.
A wave port is the most commonly used type
of excitation in HFSS. And, the wave port
represents the region or the area where the
energy enters or sources the solution space
And, this port therefore is literally
suited to sourcing structures
that are good transmission lines such as
Microstrips, Strip lines, Coaxial or Waveguide
transmission line. And, the wave port
should be applied only at the outer
faces of the solution volume.
And, the wave port yields S, Y, Z parameters,
characteristic wave impedance and gamma,
the propagation and attenuation constant.
The S-parameters that are produced
by the wave port are generalized
and can be viewed as S-parameters that
use the frequency dependent characteristic
wave impedance of the port as their
normalization constant.
A key consideration when getting a wave port
is the port size. The stated wave ports
are regions where
energy enters into the solution space.
So, wave ports are also attached
to the virtual waveguide and this is the
fundamental reason why the exact size
of a wave port is important.
HFSS generates a solution by exciting
each wave port individually,
where, each desired incident mode contains
1 Watt of time average power
And, to find a solution to a given port
the desired port
is energized with 1 Watt of power
while all the other ports in the
simulation are set to 0 Watts,
to zero incident power. And, wave ports
can be used either in the driven mode
solution type or the driven terminal solution type
Depending on the solution type chosen,
the wave port setup is slightly different.
When you create a wave port in a driven
modal solution type,
the user, you, must specify the number of
modes desired.
And, for waveguide simulations the
determination
of the needed or the wanted modes is
pretty straight-forward
but, when a wave port is used to source
a transmission line
such as a microstrip line the number of
modes should be set equal to the number
of signal traces that are enclosed
within the given wave port.
For instance, for a clone planar pair of
microstrip lines
enclosed within a single wave port,
two modes should be specified.
And, in the final solution
these two modes represents the even and
odd modes of propagation.
So, the user should also
set an integration line in the port
and while the integration line allows
the calculation
of the voltage-based wave impedance
that's traveling
on the transmission line it also serves
as a phase reference. So, as a result the
integration line
should be drawn in a consistent fashion
for all the ports.
If the integration lines are drawn
in a non-consistent manner on the
different ports
you can artificially induce a 180 degree
phase shift. So it's good modeling practice
to draw the integration lines between
the points of the maximum potential
difference in a wave port
And, when creating the wave port in the
driven terminal solution type,
the location and the number of modes
needed is automatically determined by HFSS
Additionally, the proper number of
integration lines needed is also
automatically created by HFSS.
Lumped ports are the other commonly used
excitation type in HFSS
and this port type is analogous to a
current sheet source
and it can also be used to excite
commonly used transmission lines
Lumped ports are also useful to excite
voltage gaps
or other instances where the wave ports are not
applicable. They should only be applied
internally, to the solution space.
And, lumped ports are
ports that can be used in simulations
where energy needs to be sourced
internally to a model. The ports are
simpler to create than wave ports
and that they don't yield as much information
as wave ports. So, lumped ports can yield
the S Y and Z parameters and fields, but they
don't provide the gamma or the wave
impedance information.
And, the results of a lumped port cannot
be de-embedded, but can be pre-normalized
and, unlike to the wave ports a lumped port
can support only one single mode of
propagation.
A lumped port can be defined on
any 2D object that has edges which contact
two conducting objects and the boundary
that is applied to
all edges that do not touch a conductor
is defaulted to be a perfect H
and that ensures that the normal
electric field is equal to zero Watts
on those edges.
And, when you're creating a lumped port
it's necessary
that you draw an integration line for
each port
And, the integration line should be drawn
between the center
points of the edges that contact the
conductor or metal objects.
And, the complex impedance that's defined
when the port was created
serves as the reference impedance of the
S matrix of the lumped port.
And, that impedance has the characteristics
of a wave impedance and is used to
determine the strength of the source
such as the modal voltage V and the
modal current I
and do the complex power normalization.
And, the main differentiator between the
lumped port and the wave port
is the location of where they're applied
in the model.
The wave ports in general should be
applied to the outer faces
of your solution space, outside your volume.
And, lumped ports should only be used
internal to the solution space.
So, another key difference is that wave
ports are specifically
suited to source good transmission lines
and while lumped ports are well suited to
source structures
that are not good transmission lines
such as BGAs, Wire bonds etc.
So, in this video we reviewed the most
commonly used ports
inside the Ansys HFSS EM simulation tool,
wave ports and lumped ports. And, port setup
is very important as they define the
excitation or the signal
that induces the field response
inside your model geometry.
And, in ADAS collision avoidance applications,
signal tracking along with the
electromagnetic field response
in your sensor design is not only
essential but is necessary!!
Thank you for watching this video!