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Introduction to EM Simulation

Microwave Office Training. Introduction to EM Simulation. EM Simulation. EM simulation setup has changed in 7.5. EM uses drawing layers. Case 1: Draw and Simulate a Structure in the EM Environment. Case 2: Using a Layout Created in the EM Environment in normal layout.

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Introduction to EM Simulation

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  1. Microwave Office Training Introduction to EM Simulation

  2. EM Simulation • EM simulation setup has changed in 7.5. • EM uses drawing layers. • Case 1: Draw and Simulate a Structure in the EM Environment. • Case 2: Using a Layout Created in the EM Environment in normal layout. • Case 3: Importing DXF and GDSII Layouts Into EM. • Case 4: Extracting layout from the Schematic Layout. EM Simulation

  3. The EM Environment Step 1: Open up the project 4Layer_PCB_Start.emp. This is the EM Socket. Projects go in here. To create a project - RC on EM Structures. The various EM simulators - we are using EMSight. EM Simulation

  4. EM Enclosure Settings • The Enclosure menu controls many of the important features of EM: • X and Y box dimensions, and grid size. • Bulk material properties. • Dielectric Layer Setup. • The conducting line properties - layer, conductivity, and thickness. • EM Layer Mapping (Used when working with schematic layout and artwork cells. Note: Later we will be seeing the Stackup Element for extraction. It is almost the same as the Enclosure (with some extra features). EM Simulation

  5. EM Enclosure Settings - 2 Enclosure Sets the x and y dimensions of the enclosing box. The height (z) we set later. Sets the grid in the x and y directions. You want the box size a whole number of cells. EM Simulation

  6. Grid Size Tips • Lines should be 3 to 5 cells wide. • Edge couplers might require more. • Box size - Don’t have the wall too close to nearest metal ... two substrate heights away is good. • Make sure gaps / spacing in filters is an integer number of cells. • If possible - start on a simple problem you know the answer to - simple bend, open line, 2 coupled lines,... • Gives you an idea how many cells to use. • Double your number of cells and see if your answer changes a lot. Note: 1000 unknowns - runs in 30 seconds/frequency. Solution time grows as N3...10,000 unknowns - 30,000 seconds/frequency. Number of Unknowns. EM Simulation

  7. EM Enclosure Settings - 3 Material Definitions Adding Dielectrics Conductor Properties Used for Surface Impedances New in 7.5 - Preset values remember materials you added before. EM Simulation

  8. EM Enclosure Settings - 4 Dielectric Layers Draw scale used for 3D visibility. Materials can be picked from the list of Dielectrics. New in 7.5 - Place the mouse on a layer to see its properties. Can set the top and bottom Boundary Conditions. EM Simulation

  9. EM Enclosure Settings - 5 Materials New in 7.5: Perfect Conductor will always exist - made out of material definition - Perfect Conductor. • Sets the conducting lines properties: • The thickness of the line. • What it’s made of (from list of Conductors in Material Definitions). Note: Etch Angle and Roughness are reserved for future use. EM Simulation

  10. EM Enclosure Settings - 2 EM Layer Mapping New in 7.5: This mapping is in the Enclosure Options. This controls how drawing layers are mapped to EM layers. We’ll worry about it later. EM Simulation

  11. Drawing in the EM Environment • To draw in EM: • Select an EM Layer. • Select Material. • Select Conductor or Via. Extent is how many layers down the via extends. New in 7.5: The stackup display shows you the layer you are on. EM Simulation

  12. Drawing in the EM Environment - 2 Step 2: Draw a line - 60 mils wide - layer 3 to layer 4 connected by a via (50X60mils). Use material - c - as the conductor. New in 7.5: There is not any separate button for vias. Draw Tools EM Simulation

  13. Drawing in the EM Environment - 3 3D View The 3D view shows the structure to be simulated. New in 7.5: Always check the 3D view - it will only show what is being included in the simulation. EM Simulation

  14. Drawing in the EM Environment - 4 Adding Edge Ports EM Structure Layout • Step 3: Add an edge port to each of the lines. • Select the line. • Select the edge port icon, and click at the end of the line. • Double click the edge port and use the drag handles to select the deembedding length. EM Simulation

  15. Ports You can double click on a port and change its impedance. Also can change how much power goes into it. Note: This only affects current and antenna pattern viewing. S parameters are not changed. • There are 3 kinds of ports: • Edge Ports - Like network analyzer hooking up at edges of structure. • Via Port - One port to top or bottom of box (ground). Like 1 point probe. • Internal Port - Across gap - like 2 point probe. There are 3 Webinars in KB on this - EM Simulation: A Look Under the Hood: 1, 2, 3. Tip: Be careful! Where is ground for an internal port? EM Simulation

  16. Drawing in the EM Environment - 5 Properties of an EM Shape RC on any shape - Properties. You can change a shape’s material and EM layer. You can see the shape properties in the Lower left corner of the UI. Note: The Mesh Options Tab controls how finely a shape is meshed. You normally don’t change this - unless you want to override default automesh settings. EM Simulation

  17. Drawing in the EM Environment - 6 Showing Only Active Layer New in 7.5: There are various new viewing options for understanding layers. RC in the stackup display - Hide Shapes on Non-active Layers. In this example - only layer 3 conductors and vias will be visible. Tip: You can use the mouse wheel to go through the layers. EM Simulation

  18. EM Simulation Options RC to set solver options. RC on project to get individual project options. Some global options under: Options > EM Options. This tab is simulator specific. EM Options for an EM Structure EM Simulation

  19. EM Simulation Options - 2 Frequency Control Project frequencies can be overridden locally. Tip: Often you want fewer EM frequencies because of long simulation times. You can set the meshing frequency if you wish. EM Simulation

  20. EM Simulation Options - 3 Advanced Frequency Sweep AFS - simulates over frequency band with (hopefully) fewer frequencies and (hopefully) more accuracy than just set, discrete frequencies. EM Simulation

  21. EM Simulation Options - 4 AFS adds frequency points up to the maximum - until convergence is reached. You can specify a band besides the default if you want. Note: When AFS is finished, the frequency points displayed in graphing will be the original points in the frequency tab... So - you might want to set at a high number. EM Simulation

  22. EM and Normal Layout • Schematic Layout and Artwork Cells use Drawing layers that have already been named. • The EM Mapping file is used to give drawing layers material properties (conductivity and thickness) and layer position. • There are a number of scenarios where this is needed: • Importing Artwork cells to EM for simulation. • Using an EM layout in schematic layout. • Extracting a circuit’s schematic layout to EM layout. EM Simulation

  23. Using an EM Layout in Schematic Layout When we created our EM project - what drawing layers did it use? Remember - If you can see it, it’s a drawing layer! Answer - it autogenerated these drawing layers. Note: All autogenerated EM layers begin in +. So long as we are only in EM - this is fine. But - what happens if we use this layout in the schematic layout? EM Simulation

  24. Using an EM Layout in Schematic Layout - 2 Step 4: Create a new schematic - EM_as_Sub-circuit. - Add the EM Structure as a sub-circuit. Layout View It draws on the error layer. Schematic View The problem is the schematic layout has no idea where to put the auto-generated layers. EM Simulation

  25. Using an EM Layout in Schematic Layout - 3 The secret is to understand the EM mapping file. It lives in the LPF file. All layouts - schematic layout, artwork cells, EM projects ... have an LPF file. All LPF files have an EM mapping file - it tells the materials and line position in the stackup for each drawing layer. EM Mapping file for EM project - start. These 3 layers have material and EM layer position. Note: Layer number is top of dielectric layer. EM Simulation

  26. Using an EM Layout in Schematic Layout - 4 The schematic layout uses the default project LPF, and its EM Mapping. Default LPF for project. This is why it doesn’t know what to do with the autogenerated layers... They aren’t even defined in the schematic layout LPF. EM Simulation

  27. Using an EM Layout in Schematic Layout - 5 • To fix the problem - • The EM project’s LPF was generated from the project LPF - then the autogenerated layers were added. • We fix the project LPF - so that any EM project we create will have the right mapping. Note: A common mistake is to misspell the material name. Modified default LPF. Step 5: Modify 4LayerPCB.lpf. EM Simulation

  28. Using an EM Layout in Schematic Layout - 6 Step 6: Update the dependent LPFs (i.e. the EM projects created). RC on the LPF in Layer Setup - and Update. You can select the Dependent LPFs to update. EM Simulation

  29. Using an EM Layout in Schematic Layout - 7 The EM auto generated layers have disappeared. Schematic Layout They aren’t needed. For example, it knows if you want a conductor on em layer 3, you are on drawing layer met2. Note: Any new EM projects will also have this mapping - as they are generated from the default project LPF. EM Simulation

  30. Options for Viewing Layers There are a variety of viewing options. • RC in the drawing layers pane. • Options for viewing: • Shapes on unmapped layers. • Shapes on mapped layers. • Shapes on missing layers. I’ve uncloaked all unmapped layers. An X indicates unmapped. Tip: The 3D EM view only shows mapped layers. Good way to see what is really simulating. EM Simulation

  31. Multiple EM Mapping Files You can have multiple EM Mapping Files. You can create these for the project LPF, or for EM Mapping File for a given project. • Examples: • Switch between lossy lines and perfect conductors. • In MMIC - might not want to map to EM all metal layers. Different EM Mappings Different LPF files. EM Simulation

  32. Importing DXF and GDSII into EM • External World • GDSII Libraries • DXF Libraries Artwork Cell Layout Looks for Model Layers by same name - or creates them. Step 7: Import mypad.dxf. • EM Layout • Method 1: • Copy and paste the drawing layers. • Select the shapes and change the layers. • Method 2: • Change the EM Mapping file - so can repeatedly use the mapping in the future. EM Simulation

  33. Method 1: Import and Change the Layers Step 8: Copy the EM project - start. Rename the copy to Via_Sim. - Delete the structures. Tip: One way to make many EM projects with same settings - is to copy an empty EM project. Step 9: Copy and paste the artwork cell - New_DXF_Cell into the EM Project. - You can use Ctrl - C, Ctrl - V. EM Simulation

  34. Method 1: Import and Change the Layers - 2 It’s placed on the Error layer. You can fix it by selecting the properties of each element ... and moving it to the right drawing layer. Step 10: Set the shapes on TopMetal to met1... the shape on Pad to EMLayer 2, Via. Settings for TopMetal Settings for Pad EM Simulation

  35. Method 1: Import and Change the Layers - 3 To finish it up - you would change the box size, and extend the line and add a port. EM Simulation

  36. Method 2: Update the EM Mapping in the LPF File Step 11: Create a new EM Mapping - call it PadMap. Step 12: Setup the mapping or Pad and TopMetal. Note: We could have just modified the Default Mapping - but this gives us practice with multiple EM Mappings. EM Simulation

  37. Method 2: Update the EM Mapping in the LPF File - 2 Step 13: Copy the EM Project - start - rename it to Pad_with_Mapping. - Delete the shapes. Step 14: Update Dependent LPF’s - select only +Pad_with_Mapping. EM Simulation

  38. Method 2: Update the EM Mapping in the LPF File - 3 You have the EM Mappings from the LPF in the EM project. Select PadMap - and you can now import the shapes. EM Simulation

  39. EM Extraction • Extraction sends selected PCells and other shapes to the EM Socket. • Advantages • Drawing carried out by the PCells. • As schematic layout changes - can keep sending new layout to EM simulator easily. • Ports, and deembedding lines are automatically included. • S parameter results are automatically brought back into the schematic and re-simulated. • Disadvantages • Almost too easy! Never see the EM layout. • Box can be too small, wrong layers, boundary conditions... • Can get off mesh. EM Simulation

  40. EM Extraction - 2 Step 15: Open up the project double_stub.emp. EM Simulation

  41. EM Extraction - 3 Simulation Results. Make sure the layout is connected. EM Simulation

  42. EM Extraction -4 To extract the circuit to EM we need two elements. The Extraction Element • Controls • Size of enclosure and mesh • Simulator Type • What elements are extracted. The Stackup Element Elements > Simulation Control • Controls • Layers, Materials, ... • It’s essentially the same as Enclosure with extra feature of Line Type extractions. Elements > Substrates EM Simulation

  43. EM Extraction - 5 Step 16: Add the Extraction block to the schematic and configure it. EM_Doc - The EM Project created. Name - The extraction group name. Note: Put in “ “. Extension - The box will be this much bigger than nearest conductor. EM Simulation

  44. EM Extraction - 6 Step 17: Configure the Stackup block. EM Simulation

  45. EM Extraction - 7 Note: When you change the mapping file - you will get a warning ... next slide. EM Simulation

  46. EM Extraction - 8 Line Type Mapping - This can be used as an alternative to EM mapping - when you setting up what EM Layer and Material for a Line Type to use. Note: It is normally used with iNets. EM Simulation

  47. EM Extraction - 8 The project LPF - will be changed to the new EM Mapping file. Be careful before you do this. Tip: Make a new EM mapping file - before you do this - so you don’t overwrite the original. EM Simulation

  48. EM Extraction - 9 Step 18: Select all the elements. - RC on properties - enable all of them for extraction under Model Options. Don’t use quotes! EM Simulation

  49. EM Extraction - 10 Selecting the Extract block shows the elements are enabled for extraction. EM Simulation

  50. EM Extraction - 11 Step 19: RC on the schematic icon and Add Extraction. The EM project is created. Tip: It’s always a good idea to check things over the first time you extract. Look at the 3D, etc. EM Simulation

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