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Re: gEDA-user: gschem: directly connecting two nets?

On 1/26/2011 12:34 PM, Stephan Boettcher wrote:
Peter Clifton<pcjc2@xxxxxxxxx>  writes:

On Mon, 2011-01-24 at 07:48 -0800, Ouabache Designworks wrote:
The special symbols is supposed to fuse netnames as issued on the
    not labels on the schematic.
    If you are also fusing the copper on the board then I would kind of
    like to see that when I am viewing the schematic.
    You want to give the user a choice. If I pull up a component view then
    I want to see the signal names from the original designer. If I am
    traversing a hierarchy and open an instance view then I want to see the
    signal names that match the names in the parent instance.
    John Eaton
For a loop antenna, for example, the solution needs to be in PCB.. allow
footprints / "functional groups" which implement RF components by
placing copper on some layer.

For me, this raises a very interesting design question:

How do I go from abstract inductor / transmission line / (capacitance
even?) representations on a schematic, to correctly DRC'd board layout?
This will probably require an additional tool.  The tool needs to
extract the properties of the wiring from the layout via some techology
file that describes the properties of the board materials (layer stack,

The schematic will have attributes on nets that spec what to check for.
IMHO, net segments should be explicitly marked with the short-symbol
that was discussed.  A gnetlist backend will provide a netlist to the
verification tool that includes the attributes and net segments.  The
PCB gnetlist backend merges the net segments.  How to split out the net
segments during extraction is probably not easy.

The inductor will end up as a shaped piece of copper tracking, and at
this point, you realise that "net" is a very DC term!
The inductor could be a subschematic with shorted pins via two short
symbols, with a net in between that asks for an inductance check of
some sort.

We would need to have some way to demarcate the start and end of the
inductor in PCB, or to draw it on a layer, or with an attribute which
causes the copper making up the "component" to be disjoint from either
net connecting to that section. That piece of board layout becomes a
"component", not an interconnect between components.
The DRC could be told to treat certain layers in a group as component

One might imagine a similar method being useful to join two
hierarchically shorted nets together... have a "link" component which
joins AGND and DGND, which is implemented by copper drawn on the board
between those two power planes.

This would then allow preservation of important DRC checks such as
making sure the correct plane / return path is used for signals.

I guess I am missing something significant with this. Why wouldn't the inductor just be a component on the schematic and a component in layout just like any other inductor? The only difference is that the footprint defined for the component would be the copper that makes up the antenna. It would have a pad on each end for the signal connection. Is arbitrary copper in a footprint not supported?

As to DRC, I would think design of an antenna would be a pretty complex thing to analyze automatically. A 3D field solver comes to mind. Is any of that capability currently interfaced with these tools?


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