The Params page

This page provides entry areas for parameters used by the interface.

FhUnits
This is an option menu which is used to set the length units used in files produced by the interface. Choices are meters, centimeters, millimeters, microns (the default), inches, and mils. The selection, if not the default, will set the FhUnits variable. Similarly, setting the variable with the !set command will update the state of the menu. The choice currently in effect will be applied when input files are generated. The choice of units will not affect the computed inductance/resistance.

FhManhGridCnt
Value: real number 1e2-1e5.
When a non-Manhattan polygon is ``Manhattanized'' for FastHenry, it is converted to an approximating Manhattan polygon. The value in this entry is used to set the minimum rectangle width and height allowed in the decomposition. It sets, and is set by, the FhManhGridCnt variable. The minimum size is given by

sqrt(area_of_interest/FhManhGridCnt)

The default entry value is 1000. Larger values are more accurate but slow processing, sometimes dramatically. The area_of_interest is the layout area being processed for input to FastHenry.

FhDefaults
Any text entered into this area will be included in a .defaults line in FastHenry input. The text must be understood by the FastHenry program in use. The text will also be saved in and track the FhDefaults variable.

FhDefNhinc
This entry tracks the value of the FhDefNhinc variable, which sets a default value for the FastHenry nhinc parameter. This will be overridden by values set by the layer keyword FH_nhinc in the technology file, unless the FhOverride variable is set, in which case the variable has precedence.

FhDefRh
This entry tracks the value of the FhDefRh variable, which sets a default value for the FastHenry rh parameter. This will be overridden by values set by the layer keyword FH_rh in the technology file, unless the FhOverride variable is set, in which case the variable has precedence.

Override Layer NHINC, RH
When this check box is set, the values of the FhDefNhinc and FhDefRh entries override values set with technology file keywords on individual layers. This tracks the state of the FhOverride variable (set or not).

Use FastHenry Internal NHINC, RH
If set, the >nhinc and rh values are passed to FastHenry, which will use the values internally for filament generation. If not set, the values will be used in the input file generation to refine segments according to the same parameters, and FastHenry will not create additional filaments. This button tracks the state of the FhUseFilament variable (set or not).

The FastHenry Volume Element Refinement allows one to crudely refine the raw segmentation. By default, this is not enabled, so that only tiling provides refinement. This may be a good starting point for a third-party refinement algorithm, but with present FastHenry programs is unlikely to provide accurate results as-is. When enabled, the crude refinement should provide somewhat better results.

The refinement algorithm works as follows. For each conductor, find the volume and divide by the film thickness. The maximum size is taken as the square root of the sum of these terms divided by the FhVolElTarget as entered. If a side of a tile exceeds this length, it is subdivided. This is repeated until no tiles have sides larger than the calculated length. The total number of tiles (or ``volume elements'') is approximately the target value entgered. The total number of segments is approximately six times larger.

Additionally, a minimum dimension can be defined. Volume elements with a dimension smaller than the minimum will be ignored.

The refinement is ``crude'' due to each refined volume element being approximately the same size. If the size is small enough, sufficient spatial resolution for accurate calculation is achieved. This resolution is needed along edges, and at corners, where there are strong field gradients, but is gross overkill for most areas. Since the solving time is related to the total number of segments, this type of refinement is very inefficient with respect to memory use and execution speed.

Enable
This check box will enable or disable the refinement. When pressed, the two numerical entry areas will become un-grayed, and internally the FhVolElTarget variable will be set to the number shown in the FhVolElTarget entry area, and the FfVolElMin variable will be set to the number shown in the FhVolElMin entry area. When the Enable button is set inactive, the FhVolElTarget and FhVolElMin variables are unset. The FhVolEnable variable tracks the state (set or unset) of the Enable button.

FhVolElTarget
This entry area is sensitive only when the Enable check box is checked. It tracks the value of the FhVolElTarget variable, which can be set to a real value of 1e2 - 1e5. This will be the approximate number of refined tiles generated in the input file.

FhVolElMin
This entry area is sensitive only when the Enable check box is checked. It tracks the value of the FhVolElMin variable, which can be set to a real value of 0 - 1.0. Volume elements with a dimension smaller that this fraction of the maximum dimension computed for the volume element target will be ignored.