8 EM Simulation

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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 EMEnvironment.

Case 2: Using a Layout Created in the EM Environment innormal layout.

Case 3: Importing DXF and GDSII Layouts Into EM.

Case 4: Extracting layout from the Schematic Layout.


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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 EMsimulators - we are

using EMSight.

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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 andartwork cells.

Note: Later we will

be seeing theStackup Element for

extraction.

It is almost the same

as the Enclosure

(with some extra

features).


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EM Enclosure Settings - 2

Sets the x and y dimensions of the enclosing box. The height (z) weset later.

Sets the grid in the x and y directions. You want the box size a wholenumber of cells.

Enclosure

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Grid Size Tips

Lines should be 3 to 5 cells wide.

Edge couplers might require more.

Box size - Dont have the wall too close to nearestmetal ... two substrate heights away is good.

Make sure gaps / spacing in filters is an integernumber of cells.

If possible - start on a simple problem you know theanswer 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 answerchanges 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.


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EM Enclosure Settings - 3Material Definitions

Adding Dielectrics

Conductor Properties

Used for Surface Impedances

New in 7.5 - Preset values remember materials you added before.

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Dielectric Layers

Materials can be picked from

the list of Dielectrics.

Draw scaleused 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.


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9 EM Simulation


Materials

Sets the conducting lines properties:

The thickness of the line.

What its 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 - PerfectConductor.

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EM Layer Mapping

This controls how drawing layers are mapped to EM layers. Wellworry about it later.

New in 7.5: This mapping is in the Enclosure Options.


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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.

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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 isnot any separate

button for vias.


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3D View

The 3D view shows the

structure to be simulated.

New in 7.5: Always check the

3D view - it will only showwhat is being included in the

simulation.

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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 StructureLayout


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Ports

You can double click

on a port and changeits 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 networkanalyzer hooking up at edges

of structure.

Via Port - One port to top orbottom of box (ground). Like 1point 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 LookUnder the Hood: 1, 2, 3.

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Properties of an EM Shape

RC on any shape- Properties.

You can change a shapes material and EM layer.

Note: The Mesh Options Tab controls how finely a shape is

meshed. You normally dont change this - unless you want tooverride default automesh settings.

You can see the shape properties in the Lower left corner of the UI.


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Showing Only Active LayerNew 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 3conductors and vias will be

visible.

Tip: You can use the mouse wheel to go through the layers.

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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.


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EM Simulation Options - 2

Frequency Control

Project frequencies can

be overridden locally.

You can set themeshing frequency if

you wish.

Tip: Often you wantfewer EM

frequencies

because of longsimulation times.

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Advanced Frequency Sweep

AFS - simulates over frequency band with (hopefully) fewer frequencies

and (hopefully) more accuracy than just set, discrete frequencies.


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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 thefrequency tab... So - you might want to set at a high

number.

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EM and Normal Layout

Schematic Layout and Artwork Cells use Drawing layers that havealready 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 circuits schematic layout to EM layout.


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Using an EM Layout in SchematicLayout

When we created our EM project - what drawing layers did it use?

Remember - If you can see it, its 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?

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Using an EM Layout in SchematicLayout - 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.


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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 materialsand 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.

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Default LPF forproject.

The schematic layout uses the default project LPF, and

its EM Mapping.

This is why it doesnt know what to do with the autogenerated layers...

They arent even defined in the schematic layout LPF.


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To fix the problem - The EM projects 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 commonmistake is to

misspell the

material name.

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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.


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Schematic Layout

The EM auto

generated layers

have disappeared.

They arent needed. For example, itknows if you want a conductor on em

layer 3, you are on drawing layer

met2.

Note: Any new EM projects will alsohave this mapping - as they are

generated from the default project LPF.

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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.

Ive uncloaked all unmapped

layers. An X indicates unmapped.

Tip: The 3D EM view only showsmapped layers. Good way to see

what is really simulating.


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Multiple EM Mapping Files

You can have multiple EM Mapping Files. You can create these forthe project LPF, or for EM Mapping File for a given project.

Different EM

Mappings

Examples:

Switch between

lossy lines and

perfectconductors.

In MMIC - mightnot want to map

to EM all metallayers.

Different LPF files.

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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 canrepeatedly use the mapping in the future.


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Method 1: Import and Change theLayers

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.

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Method 1: Import and Change theLayers - 2

Its 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


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Method 1: Import and Change theLayers - 3

To finish it up - you would change the box size, and extend the

line and add a port.

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Method 2: Update the EM Mapping inthe 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.


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Method 2: Update the EM Mapping inthe LPF File - 2

Step 13: Copy the EM Project - start - rename it to Pad_with_Mapping.

- Delete the shapes.

Step 14: Update Dependent LPFs - select only+Pad_with_Mapping.

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Method 2: Update the EM Mapping inthe LPF File - 3

You have the EM Mappings from the LPF in the EM project.Select PadMap - and you can now import the shapes.


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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.

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EM Extraction - 2

Step 15: Open up the project double_stub.emp.


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EM Extraction - 3

Make sure the layout is connected. Simulation Results.

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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, ...

Its essentially the same as Enclosure withextra feature of Line Type extractions.


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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 thismuch bigger than nearest

conductor.

Note: Put in .

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EM Extraction - 6

Step 17: Configure the Stackup block.


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EM Extraction - 7

Note: When you

change the mappingfile - you will get a

warning ... nextslide.

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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 aLine Type to use.

Note: It is normally used with iNets.


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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

dont overwrite the original.

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EM Extraction - 9

Step 18: Select all the elements.

- RC on properties - enable all of them for extraction under

Model Options.

Dont use quotes!


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EM Extraction - 10

Selecting the Extract block shows the elements are enabled

for extraction.

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EM Extraction - 11

Step 19: RC on the schematic icon and Add Extraction.

The EM project is created.

Tip: Its always agood idea to checkthings over the first

time you extract.Look at the 3D, etc.


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EM Extraction - 12

Step 20: Enable AFS for the EM Project.

Simulate - and look at the results in the graph. Note the Sparameters are automatically updated.

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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.


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Viewing the Mesh

The mesh is viewed in the 3D view as an annotation.

Note: It doesnt need to simulate to see the mesh.

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Viewing Currents

Currents can be viewed as a 3D annotation.Note: You cannot

view currents withAFS turned on.

I disabled

AFS, and

simulated at 1

point - 20

GHz.


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Viewing Currents - 2

You can animate it - cycles throughphase.

EM 3D Layout Toolbar.

Documents

8 EM Simulation