Post on 19-Aug-2018
1
Introduction to EM SimulationIntroduction to EM SimulationIntroduction to EM SimulationIntroduction to EM Simulation
Microwave Office Training
2 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.
• Case 3: Importing DXF and GDSII Layouts Into EM.
• Case 4: Extracting layout from the Schematic Layout.
2
3 EM Simulation
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.
4 EM Simulation
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).
3
5 EM Simulation
EM Enclosure Settings - 2
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.
Enclosure
6 EM Simulation
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.
4
7 EM Simulation
EM Enclosure Settings - 3Material Definitions
Adding Dielectrics
Conductor Properties
Used for Surface Impedances
New in 7.5 - Preset values remember materials you added before.
8 EM Simulation
EM Enclosure Settings - 4
Dielectric Layers
Materials can be picked from the list of Dielectrics.
Draw scale used for 3D visibility.
New in 7.5 - Place the mouse on a layer to see its properties.
Can set the top and bottom Boundary Conditions.
5
9 EM Simulation
EM Enclosure Settings - 5
Materials
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.
New in 7.5: Perfect Conductor will always exist -made out of material definition - Perfect Conductor.
10 EM Simulation
EM Enclosure Settings - 2
EM Layer Mapping
This controls how drawing layers are mapped to EM layers. We’ll worry about it later.
New in 7.5: This mapping is in the Enclosure Options.
6
11 EM Simulation
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.
12 EM Simulation
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.
Draw Tools
New in 7.5: There is not any separate button for vias.
7
13 EM Simulation
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.
14 EM Simulation
Drawing in the EM Environment - 4
Adding Edge Ports
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 Structure
Layout
8
15 EM Simulation
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.
Tip: Be careful! Where is ground for an internal port?
There are 3 Webinars in KB on
this - EM Simulation: A Look
Under the Hood: 1, 2, 3.
16 EM Simulation
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.
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.
You can see the shape properties in the Lower left corner of the UI.
9
17 EM Simulation
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.
18 EM Simulation
EM Simulation Options
RC to set solver options.
RC on project to get individual project options.
Some global options under: Options > EM Options.
EM Options for an EM Structure
This tab is simulator specific.
10
19 EM Simulation
EM Simulation Options - 2
Frequency Control
Project frequencies can be overridden locally.
You can set the
meshing frequency if
you wish.
Tip: Often you want fewer EM frequencies
because of long simulation times.
20 EM Simulation
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.
11
21 EM Simulation
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.
22 EM Simulation
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.
12
23 EM Simulation
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?
24 EM Simulation
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.
Schematic View
Layout View
It draws on the error layer.
The problem is the schematic layout has no idea where to put the auto-
generated layers.
13
25 EM Simulation
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.
26 EM Simulation
Using an EM Layout in Schematic Layout - 4
Default LPF for
project.
The schematic layout uses the default project LPF, and its EM Mapping.
This is why it doesn’t know what to do with the autogenerated layers...
They aren’t even defined in the schematic layout LPF.
14
27 EM Simulation
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.
Step 5: Modify 4LayerPCB.lpf.
Modified default LPF. Note: A common mistake is to misspell the
material name.
28 EM Simulation
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.
15
29 EM Simulation
Using an EM Layout in Schematic Layout - 7
Schematic Layout
The EM auto
generated layers
have disappeared.
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.
30 EM Simulation
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.
16
31 EM Simulation
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.
Different EM
Mappings
Examples:
• Switch between lossy lines and perfect conductors.
•In MMIC - might not want to map
to EM all metal layers.
Different LPF files.
32 EM Simulation
Importing DXF and GDSII into EM
External World
• GDSII Libraries
•DXF Libraries
Artwork Cell Layout
EM Layout
Looks for Model
Layers by same
name - or
creates them.Step 7: Import mypad.dxf.
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.
17
33 EM Simulation
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_Cellinto the EM Project.
- You can use Ctrl - C, Ctrl - V.
34 EM Simulation
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
18
35 EM Simulation
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.
36 EM Simulation
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.
19
37 EM Simulation
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.
38 EM Simulation
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.
20
39 EM Simulation
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.
40 EM Simulation
EM Extraction - 2
Step 15: Open up the project double_stub.emp.
21
41 EM Simulation
EM Extraction - 3
Make sure the layout is connected. Simulation Results.
42 EM Simulation
EM Extraction -4
To extract the circuit to EM we need two elements.
The Extraction Element
Elements > Simulation Control
Elements > Substrates
The Stackup Element
Controls
• Size of enclosure and mesh
•Simulator Type
•What elements are extracted.
Controls
• Layers, Materials, ...
•It’s essentially the same as Enclosure with
extra feature of Line Type extractions.
22
43 EM Simulation
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.
Extension - The box will be this
much bigger than nearest
conductor.
Note: Put in “ “.
44 EM Simulation
EM Extraction - 6
Step 17: Configure the Stackup block.
23
45 EM Simulation
EM Extraction - 7
Note: When you change the mapping file - you will get a
warning ... next slide.
46 EM Simulation
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.
24
47 EM Simulation
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.
48 EM Simulation
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!
25
49 EM Simulation
EM Extraction - 10
Selecting the Extract block shows the elements are enabled for extraction.
50 EM Simulation
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.
26
51 EM Simulation
EM Extraction - 12
Step 20: Enable AFS for the EM Project.
Simulate - and look at the results in the graph. Note the S parameters are automatically updated.
52 EM Simulation
EM Extraction - 13
Note: After simulating the EM:
• I froze the traces: Ctrl - F.
•Went to the schematic and disabled the Extraction Block.
•Resimulated. There is a large difference in filter response.
27
53 EM Simulation
Viewing the Mesh
The mesh is viewed in the 3D view as an annotation.
Note: It doesn’t need to simulate to see the mesh.
54 EM Simulation
Viewing Currents
Currents can be viewed as a 3D annotation.Note: You cannot view currents with AFS turned on.
I disabled AFS, and simulated at 1
point - 20 GHz.