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Best Practices for Efficient and Effective Planar EM Simulation 6 www.cadence.com/go/awr An EM simulator needs to know which polygons in the layout are supposed to be in the EM layout; in other words, they represent metal shapes on board layers. The EM mapping file maps the appropriate draw layers over to the EM stackup of physical layers. For example, in Figure 5, any polygon drawn on the Cu_01 draw layer is mapped over to the top of the third layer of the dielectric stackup. The layers are numbered from top to bottom of the stackup with the air above being Layer 1. In this example, Layer 2 is the solder mask. Layer 3 is the polytetrafluoroethylene (PTFE). The polygon is placed on top of Layer 3, which is the top of the PTFE. As another example, the draw layer Via01_02 is mapped to the top of dielectric STACKUP 3, which is the top of the PTFE. The box is checked to the right of the table, meaning the shape is a via going downward one layer (the via extent is set to 1). Figure 5: The EM mapping table (right), materials tab showing Cu01 (top right), and bulk copper defined under the Material Definitions tab (bottom right) The AWR AXIEM simulator also needs to know how thick the polygon is and what it is made of. This information is, again, set in the EM mapping table. The material setting in the table refers to the materials tab in the STACKUP block, in which the name of the material is mapped to a bulk material name and properties and to the polygon's thickness (Figure 5). For example, polygons on the draw layer Cu_01 use a material name Cu01 from the EM mapping table. The Cu01 material name gives polygons a thickness of 0.03556 mm (0.7mm) and are made out of copper. This is assigned in the materials tab. The material copper is assigned in the conductivity section of the material definitions tab. There are two common situations where confusion can occur. Designers might try to change the mapping file in the STACKUP block, which will cause a warning message to appear stating they are about to change the mapping file in the master layer process file (LPF). This is where most of the layout settings, such as draw layer information, units, and various export mapping tables, as well as the EM mapping table, are stored. The STACKUP block displays a copy of the mapping table. The reason for this behavior is historical; the LPF file existed long before the STACKUP block was invented. Designers can go ahead and change the mapping file, provided they understand what they are doing. The second situation occurs when the external layout is brought into AWR Microwave Office software. For example, if a DXF file is imported from AutoCAD, the file has its own draw layers, which are not properly mapped to EM.

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