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USC Signal Integrity Lab Course 2

Ansoft High Frequency Structure Simulator (HFSS)

ELCT 762

USC

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Stack up

1 Copper 1OZ 1.4 Sig 5 mil / 10 mil space

FR4 DK = 4.1 5

2 copper 1 OZ 1.4 GND

FR4 DK = 4.1 47


FR4 DK = 4.1 5

4 copper 1 OZ 1.4 Sig 5 mil / 10 mil space

total thickness ( mil ) 62.6

1 mil = 0.001 inch,

Signal trace width = 5 mil

Signal to signal space = 20 mil

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Configuration

Start HFSS

Save file

Insert HFSS design Setup solution type: Driven Terminal

Setup grid to 0.1 inch

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Add signal trace

Draw a BOX at: 0, 1, 0.0598, size: 1.005, 0.005, 0.0014inch

Rename it: Trace1, Assign Material: Copper. Change thecolor to: RED

Copy Trace1, and Paste it. Now you got trace2. Changetrace2s original at 0.995, 1, 0 inch, size: 1.005, 0.005,-0.0014 inch

Now Trace1 and Trace2 are on two different sides of the

PCB. They are located at center and overlap each otherby 10mil.

In order to see both traces, you need to set transparentproperty of all drawing to be ~ 0.7

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Bolean Function - subtract

Subtract window pops up.

Move, FR4_1, FR4_2,FR4_3, GND1, GND2 toBlank Parts window

Move anti_via1 to ToolParts window

Select Clone tool objects

before subtracting Why?

Click OK

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Question.

The overlap issue between FR4, GND andanti-via is solved.

Theres another overlap error. Which one?

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Bolean function - unite

Hold Ctrl key and click: FR4_1, FR4_2, FR4_3, anti_via1

Click: 3D modeler -> Boolean -> unite

All of above items will be united into one item. Name:FR4_1. ( the new name is the first item you selected )

You can only unite the items that touch each other andhave same material

Your field solution is more accurate and process is fasterafter you unite the similar items

If you want to un-do the unite, go to command historywindow and delete the unite under FR4_1

Do the same thing to unite: trace1, trace2, via

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Create 2nd trace

In command history window, click and select: trace1

Click: edit -> copy, then click: paste

Now, you have trace3 created at the exact same locationof trace1. (they overlap each other)

Click and select: trace3

Click: Edit> arrange -> move

Use the mouse, drag trace 3 in the positive Y direction20mils. (note: DY = 0.02 indicator at bottom right)

To verify the move, in the command history window,double click the move command.

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Create 2nd trace, cont.

Now, the sub windowpops up.

Make sure the move

vector is 0, 0.02, 0 This makes the 2ndtrace 20mil away from1st trace.

What is the air gapsize between thetraces?

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2nd Anti-via

Create an anti-via for the 2nd trace. The centerlocation should be 0, 1.023, 0

Review slide 10 for creating an anti-via

Rename the new item: anti_via2

Theres an overlap issue between anti_via2 and

FR4_1, GND1, GND2, trace3. Review slides 12

and 15 to solve the overlap error Unite the FR4_1 with anti_via2. keep the name:

FR4_1 for the united item.

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Structure with 2 traces

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Add Air Box

Need to add Air boxes on top& bottom of PCB. Why?

Draw a box at 0,0, 0.598, size:2, 2, 1, Material: air, rename it:air1

Draw a box at 0, 0, 0, size 2, 2,-1, Material: air, rename it:air2

Change the color of air to:white with transparent settingof 0.95

Air boxes overlap with trace1and trace3. Use the Booleanfunction to do the subtraction

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View at different angle

Click: View -> ModifyAttribute -> Orientation

You can set the Top view,front view or side view.

This helps a lot when youdesign with 2D objects.

Now, set the view as:front view. See toppicture

Select the FR4_1 item,make the transparentproperty: 0

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Port & Terminals Sample

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Terminals

Set the view at: front view

Select by clicking: Port1

Click: HFSS -> Excitation ->Assign -> Wave Port

Click: Next , the Wave Port

terminal window pops up. Set: Number of Terminals = 2,

Click: update

Change the name of 2ndTerminal line to T3.

At T1 Terminal Line cell, click& select: New Line

Use coordinate system to keyin terminal lines

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Assign Boundary

Assign radiation boundary onexternal surface of airbox.

Click: Edit -> Select -> Face

Hold down CTRL key, andselect the external face of air1.

Hold the ALT key to rotate theobject to select faces

Click: HFSS -> Boundary ->Assign -> Radiation. Hit Enter.

In project window, click

boundary -> RAD1, theradiation boundary shows ondrawing window

Do the similar boundaryassignment for air2

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Setup another solution

Now, setup a sweepunder first solution

Click: HFSS -> AnalysisSetup -> Add Sweep.

Click OK to pick setup1

Edit Sweep windowpopup

Change Sweep type: fast

Change Sweep size: 0.5Ghz

Click OK

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Simulation!

Click: HFSS -> Analyze

Wait 15 min for this small simulation.

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S parameter

Click: HFSS -> Results ->Solution Data

Click on tab: Matrix Data Solution Data window

pops up. It shows the Sparameter matrix.

To show data for allfrequencies, click: AllFreqs.

This table gives you datafor point analysis. For ageneral AC analysis, aplot is a better way

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Plot of S11

Click: HFSS -> Results ->Create Report

Change display type:Smith Chart

Pick Report Type:Terminal S parameters.Press OK

Pick Quantity: first entry,this is S11.

Double Click this entry(trace appears at top)

Click Done

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S11 on Smith Chart

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Plot S21

Click: HFSS -> Results ->Create Report

Set Display Type: RectangularPlot

Click: OK

At Plot window, select quantity:waveport T2, T1. This is theS21

At function sub-window, select:dB. This will plot the

magnitude of S21 in dB Double Click (put entry at top)

Click: Done

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S21, Real & Image Part

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Project 1

Compare the T-lines pass via with atypical micro strip. ( no via )

Do the same simulation to find the

difference on return loss, insertion lossand cross talk

Suggest what is the cause of those

differences How to improve it? Suggestions?

Show the improved result on simulation

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Project 2

Do the same thing as project 1 for a strip line.

Copper 1 OZ 1.4

FR4 DK = 4.1 5

1 Copper 1OZ 1.4 Sig 5 mil / 10 mil space

FR4 DK = 4.1 5


FR4 DK = 4.1 47


FR4 DK = 4.1 5

4 copper 1 OZ 1.4 Sig 5 mil / 10 mil spaceFR4 DK = 4.1 5

Copper 1Oz 1.4

Class 09

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