Independent Frequencies of Interest
In earlier versions of LC, the user was required to set the frequencies of interest in the Define Model Paramerers dialog if far field data was to be obtained. The same frequencies had to be specified for each far field sweep defined, or else an error would occur. With LC 2.5, each far field sweep definition, as well as the total power radiated plot, can have its own frequencies of interest. If the total radiated power plot is not of interest, then no frequencies need be specified in the Define Model Parameters dialog at all.When a simulation is started, the sets of frequencies of interest are merged automatically. Thus, it is often most efficient to conform to the old rule and have each far field sweep include the same frequencies. However, this new capability allows much more flexibility in the collection of frequency domain far field data.
The rising and falling waveforms from an IBIS (I/O Buffer Information Specification)
file can now be used to define a source.
IBIS is defined by the ANSI/EIA-656 standard.
To define an IBIS source, specify the input file name containing the IBIS
specification for the driver and the name of the model within the file.
Either the typical, minimum, or maximum curve can be used.
If desired, the hold time between the end of the rising waveform and
the beginning of the falling waveform can be given by the Duration
parameter.
Thus, if a model requires a very small cell size in one dimension, but the
other dimensions are not so constrained, the amount of memory required by
the simulation can be greatly reduced by making the cells non-cubic.
By doubling the size of the cell along one axis, the amount of memory
required is reduced nearly in half.
Doubling the cell size in two dimensions reduces the memory requirement
to a quarter of the original.
Since there are fewer cells, there is also less computation required for
every time step. However, the calculation for each cell is a little
more complex, increasing the per-cell computation time.
So the overall speedup in run time is somewhat less than the memory
requirement reduction.
The number of contour lines to be displayed can be specified.
In this case, ten contour lines were used.
Note that the number of colors used is controlled by the same value
as the number of contour lines.
Again the number of colors was fixed at ten, rather than the default
of 100.
Line Patterns for Plotting
When multiple curves are plotted on the same graph, LC can now show the
individual curves in different colors, or as different line patterns.
These features can be selected from the View menu of the X-Y Graph dialog.
Currently, printing from the dialog menu does not support line patterns.
Automatic Run Termination
Toggle buttons are now available in the Run Start and Run Terminate dialogs
to make the simulation terminate when the time stepping is complete.
This feature is useful for forcing the far field sweeps to be calculated
automatically at the end of the simulation during interactive sessions.
IBIS Driver Source Waveforms
The rising and falling waveforms given in the IBIS file for the model
specified are combined together to create a single curve.
The plots are time-shifted and voltage-shifted to make the combined
curve continuous.
The falling waveform is placed after the end of the rising waveform data
after an optional duration or hold time has been inserted.
The first point of the falling waveform is matched to the last point of
the rising waveform to create a continuous curve.
Non-cubic Grid Cells
In the simplest formulation of FD-TD, used in LC version 2.4 and earlier,
all of the cells of the computational grid are cubes of the same size.
The dimensions of every cell are defined by a single parameter, the
cell width.
This is still the default grid type for LC, but a little more flexibility
has been added by allowing three parameters to be defined: the cell
length, width, and height.
Contour Lines For Plane Probes
In addition to the colored-cell and the shaded-cell visual formats for
plane probe display, a option for contour lines is available.
This is an image of a contour line display of an electric field plane probe
above a microstrip.
The same plane probe shown as colored cells.
Each colored cell corresponds to an FDTD cell.
The same plane probe shown as shaded cells.
Return to What's New
Copyright © Cray Inc.
Maintained by Kevin Thomas (kjt@cray.com).
Last modified
Wed Jul 1 14:43:08 CDT 1998