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Best Practices for Efficient and Effective Planar EM Simulation 5 www.cadence.com/go/awr Chapter 2: EM Environment Best Practice Tip #2: Understand how EM layer definitions work in the STACKUP block. A STACKUP block should be used when EM projects are created in AWR Microwave Office ® circuit design software. This is true not only for the AWR AXIEM simulator, but also for the AWR Analyst™ 3D finite-element method (FEM) simulator and the EMSight simulator. The STACKUP block contains the important material and layer stackup information for developing the AWR AXIEM project. The STACKUP block is usually placed in the Global Definitions page, which is in the upper-left part of the project browser. Figure 4 shows STACKUP blocks on the Global Definitions page. When the designer creates a new EM project by right clicking the EM Structures in the project browser and selecting New EM Structure, a STACKUP block must be chosen, as shown in Figure 4. (Note that while it is possible to not use a STACKUP block in the menu, it is strongly recommended to always use one. The older, obsoleted options exist for backward compatibility.) Figure 4: Two different STACKUP blocks on a Global Definitions page (left) and STACKUP block creation in a new EM project (right) The created EM project has an Enclosure folder, most of which is a copy of the STACKUP block and can be accessed by looking under the EM project tree in the project browser. The first Enclosure tab sets the grid size and did not come from the STACKUP block. This is discussed in Best Practice Tip #5 on grid settings. The settings in the Enclosure folder can be changed, but the original STACKUP block is not changed and only the local EM project is affected. Any process design kit (PDK) that a designer uses as part of a chip technology, such as a gallium arsenide (GaAs) or silicon (Si) process, will have a STACKUP defined in the global definitions. PCB designers usually do not have a PDK supplied to them and are forced to create their own STACKUP. This task can be made much easier by using the process creator that ships with AWR Microwave Office software. To access it, go to the tools menu and select Create Process. After filling in the necessary infor- mation, a library is created for the designer to use. A STACKUP has been created in the library for EM purposes. It is important that the designer have some understanding of the various parts of the STACKUP, even if it has been precon- figured. The first menus on material properties and layer STACKUP are relatively straightforward—the confusion comes when looking at the EM mapping layer table. It is important to understand the basics of this table in order to better control EM setup and correct any potential problems. Figure 5 shows the EM mapping file in a typical PCB STACKUP block. The left column lists the draw layers in the project. Draw layers are fundamental to all layout in AWR Microwave Office software because polygons are created on draw layers. A draw layer has a name, a color, and a fill pattern, and all planar layout tools use draw layers of some kind. Most of the layers have nothing to do with physical metal shapes but are needed in order to manufacture the PCB board. For example, Figure 5 shows there are draw layers with names like "Error," "Ink," and "SolderStencil." They are necessary for layout but are not used by the AWR AXIEM simulator.

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