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FastHenry Partition Editor

As was described in the section discussing terminals, the initial partition divides at all boundaries of the object, and at the boundaries of the objects on conducting layers above and below the object. This initial partitioning is generally not bad, however for greatest accuracy one may wish to further subdivide the partitions in areas with high field gradients. This will increase FastHenry execution time, but if done correctly improves accuracy. Generally, process variation leads to quite a bit of uncertainty anyway, so obtaining extreme accuracy is probably not worth the effort. The FastHenry partition editor provides the capability of refining (subdividing) the partitioning where necessary.

Pressing the Edit FastHenry Partition button in the RLC Extraction panel Partition page starts the FastHenry partition editor. The editor remains active until the Esc key is pressed, the Edit FastHenry Partition button is pressed again, or some other command is invoked which forces exit.

Initially, all partitions for all objects on all layers are displayed. Clicking on a conducting object will change the display to show only the partitioning for that object, which will be termed the ``current object''. Clicking on another object will change the display to show the new object's partitioning, and make it the current object.

Clicking on the current object will ``refine'' the partition where the user clicked. The original partition rectangle will be replaced with nine smaller rectangles that cover the same area. Pressing and dragging over the current object will refine all of the partitions that overlap the rectangle defined by dragging.

The layer-specific mode can be used to limit object selection to specific layers. This is often necessary to ensure that the button presses apply to the current object, rather than selecting another object at the same location (or vice-versa).

It is presently not possible to ``un-refine'' a partition box. However, pressing the Delete key will, for the current object, destroy all partitioning, and recreate the initial partitions.

The partitioning is remembered between invocations of the partition editor, until the interface is cleared, reset, or a new object is saved. The partitioning can be saved with the Dump Saved button in the RLC Extraction panel General page.

The interface partitions the conductors into oriented volume elements. The connection points of the volume elements are at ``nodes'' which are points in space. The nodes for adjacent volume elements must coincide for current to flow.

Since we do not know a-priori which direction current is flowing in the x-y plane, volume elements must support flow in both directions. Since the films are thin, the z-direction is ignored. A basic volume element is a rectangular prism which consists of four segments and five nodes. A ``segment'' is a rectangular parallelopiped oriented between two nodes, that carries current between the nodes. There is a node in the center of each element edge, and one in the center of the element. Two of the segments are x-directed, and two are y-directed. The x and y segments join at the central node. This element is used to tile the conductors. The tiling is such that all tiles that have a neighbor will share a node with the neighbor. The highlighted rectangles that are visible in the partition editor are the outlines of these volume elements. Given the spatial node coincidence constraint, some thought should reveal why it is necessary to refine an element by trisecting rather than, for example, bisecting. This is necessary to retain the node at the midpoint of each side of the volume element.


next up previous contents index
Next: FastCap Partition Editor Up: The FastCap/FastHenry Interface Previous: Defining FastHenry Terminals   Contents   Index
Stephen R. Whiteley 2012-04-01