by

Steve DiBartolomeo
Applications Manager
Artwork Conversion Software, Inc.

As circuits get faster it becomes necessary to have a close look at the high frequency behavior prior to building them.

Many circuits are designed using PCB layout tools that do not have the ability to do accurate simulation at RF and microwave frequencies. Nor is it possible to design a direct link between every PCB tool and every electrical simulation tool.

One approach is to take the output from a PCB layout software and to bring it into Agilent’s ADS program. The various metal layers can then be analyzed across a wide range of frequencies.

The first problem one encounters is discovering that each PCB design tool has its own unique and proprietary database. The only common format one can reliably export out of all PCB tools is the Gerber photoplot code used to make the artwork.

The second problem is that the Gerber data produced for artwork purposes is often not useful for analysis. It can contain multiple overlapping entities.

GBRUnion addresses both issues -- it converts Gerber into a format that ADS can import (EGS archive) and simultaneoulsy “cleans” the data prior to conversion by performing a boolean on all elements.

Union Cleans it Up

To clean up a Gerber file, GBRUnion runs a boolean operation on the data until no touching or overlapping polygons are found. First, each draw or flash command is converted into a boundary. Any touching or overlapping boundaries are combined into a single boundary. The process is repeated until no more union operations can be completed. Only then is the data converted into EGS archive.