Presentation on theme: "USC Signal Integrity Lab Course 2 Ansoft High Frequency Structure Simulator (HFSS) ELCT 762 USC."— Presentation transcript:
1 USC Signal Integrity Lab Course 2 Ansoft High Frequency Structure Simulator (HFSS) ELCT 762USC
2 Driven Terminal Problem Analyze two micro strip lines that pass through via. Analyze the impact of return loss and insertion loss. (S11, S21 )Use the 4 layer PCB in the following stack up.Analyze the PCB at a size of 2 x 2 inch
3 Stack up 1 mil = 0.001 inch, Signal trace width = 5 mil 1Copper 1OZ1.4Sig5 mil / 10 mil spaceFR4DK = 4.152copper 1 OZGND4734total thickness ( mil )62.61 mil = inch,Signal trace width = 5 milSignal to signal space = 20 mil
4 Configuration Start HFSS Save file Insert HFSS design Setup solution type: Driven TerminalSetup grid to 0.1 inch
5 Structure DesignDraw a BOX at: 0, 0, 0, size: 2, 2, inch. Assign material: FR4_epoxy. Set transparent: 0.7 Rename it: FR4_1Draw 2nd BOX at 0, 0, 0.005, size: 2, 2, inch. Assign material: Copper. Set transparent: 0.7 Rename it: GND1Draw 3rd BOX at 0, 0, , size: 2, 2, inch. Assign material: FR4_epoxy. Set transparent: Rename it: FR4_2Select GND1 by clicking in command history window. Click: Edit-> copy, and Edit -> Paste. Now, GND2 is copied from GND1 and is placed at the exact same location!Double Click GND2 (create box) at command history window. At property window, put 0, 0, as new origin. This moves GND2 to upper layer
6 Stack up DesignDo the same thing to copy FR4_1 and make it FR4_3. Put new origin as: 0, 0,Now the stack up is ready. It has two ground layers and 3 FR4 layers.Grey color is for FR4 and Blue is for GNDSide view of PCB stackup
7 Add signal traceDraw a BOX at: 0, 1, , size: 1.005, 0.005, inchRename it: Trace1, Assign Material: Copper. Change the color to: REDCopy Trace1, and Paste it. Now you got trace2. Change trace2’s original at 0.995, 1, 0 inch, size: 1.005, 0.005, inchNow Trace1 and Trace2 are on two different sides of the PCB. They are located at center and overlap each other by 10mil.In order to see both traces, you need to set transparent property of all drawing to be ~ 0.7
9 What is via and anti-via What is via & anti-viaWhat does via do?What does anti-via do?
10 Add via and anti-viaClick the cylinder icon, draw a cylinder between two traces.Change the current position to: 1, , 0 inch, radius: and height: inch. Assign the material: copper. Change the color: RED Rename it: via1Do another cylinder (10mil radius), assign material: Fr4_epoxy, rename it: anti_via1Two cylinders overlap and center at same location. -- this will cause a problem and confuse the software! Why?
11 Bolean functionThe overlap of two different materials will cause design error. This can be corrected by using Boolean function – subtract.In command history window, hold: Ctrl key and click: FR4_1, FR4_2, FR4_3, GND1, GND2, anti_via1This selects the 6 items above to perform a Boolean functionClick: 3D Modeler -> Boolean -> Subtract..
12 Bolean Function - subtract Subtract window pops up.Move, FR4_1, FR4_2, FR4_3, GND1, GND2 to Blank Parts windowMove anti_via1 to Tool Parts windowSelect “Clone tool objects before subtracting” Why?Click “OK”
13 View - VisibilityAfter subtraction, graphic verification is hard since all the components overlap each other. (visibility setting can solve this problem)Click: View -> visibilityVisibility window pops up. Turn off the visibility on all FR4 and anti_via1It is verified that via passed through two layers of ground without touching it
14 Question. The overlap issue between FR4, GND and anti-via is solved. There’s another overlap error. Which one?
15 Overlap problem 2 There’s overlap between anti-via and via. Use Boolean subtraction function, subtract via from the anti-via. Don’t forgot to “clone” the viaUse the visibility command to verify that anti_via1 has a hole in the center.
16 Bolean function - unite Hold Ctrl key and click: FR4_1, FR4_2, FR4_3, anti_via1Click: 3D modeler -> Boolean -> uniteAll 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 and have same materialYour field solution is more accurate and process is faster after you unite the similar itemsIf you want to un-do the “unite”, go to command history window and delete the “unite” under FR4_1Do the same thing to unite: trace1, trace2, via
17 Create 2nd trace In command history window, click and select: trace1 Click: edit -> copy, then click: pasteNow, you have trace3 created at the exact same location of trace1. (they overlap each other)Click and select: trace3Click: Edit –> arrange -> moveUse the mouse, drag trace 3 in the positive Y direction 20mils. (note: DY = 0.02 indicator at bottom right)To verify the move, in the command history window, double click the move command.
18 Create 2nd trace, cont. Now, the sub window pops up. Make sure the move vector is 0, 0.02, 0This makes the 2nd trace 20mil away from 1st trace.What is the air gap size between the traces?
19 2nd Anti-viaCreate an anti-via for the 2nd trace. The center location should be 0, 1.023, 0Review slide 10 for creating an anti-viaRename the new item: anti_via2There’s an overlap issue between anti_via2 and FR4_1, GND1, GND2, trace3. Review slides 12 and 15 to solve the overlap errorUnite the FR4_1 with anti_via2. keep the name: FR4_1 for the united item.
21 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: air1Draw a box at 0, 0, 0, size 2, 2, -1, Material: air, rename it: air2Change the color of air to: white with transparent setting of 0.95Air boxes overlap with trace1 and trace3. Use the Boolean function to do the subtraction
23 View at different angle Click: View -> Modify Attribute -> OrientationYou can set the Top view, front view or side view. This helps a lot when you design with 2D objects.Now, set the view as: front view. See top pictureSelect the FR4_1 item, make the transparent property: 0
26 Port & terminal Terminals 1 2 3 4 Port is a 2D rectangular area wh6h to 10h10w, w hor5w (3h to 4h), w < hPort is a 2D rectangular areaTerminals are each end of tracesPort contains terminals
27 Port Assignment Set the view at: Front view Draw a 2D rectangle by clicking: Draw->Rectangle ( Set in plane direction: YZ)Enter original: 2, 0.988, Y size: 0.05, Z size: -0.05Set transparency: 0.8Rename: Port1Do another 2D rectangle at: 0, 0.988, Y size: 0.05, Z size: 0.05See picture next slide.
29 Terminals Set the view at: front view Select by clicking: Port1 Click: HFSS -> Excitation -> Assign -> Wave PortClick: Next , the Wave Port terminal window pops up.Set: Number of Terminals = 2, Click: updateChange the name of 2nd Terminal line to T3.At T1 Terminal Line cell, click & select: New LineUse coordinate system to key in terminal lines
30 Terminal LinesThe terminal lines have to be on the Port1 plane. It has to go from GND1 to Trace1It is very hard to use the mouse to set the terminal line because it will snap to a point somewhere outside of the Port1 plane.It is highly recommended to key in the coordinate system below the progress windows ( lower right corner). See picture
31 Terminal lines, cont.At coordinate system, enter: 2.0, , inch for xyz. Hit: EnterEnter: 0, 0, for Delta x, y, z, hit EnterNow you got a terminal line T1 from GND1 points to trace1. It is on the Port1 plane.Note the point direction, It is point from low voltage (GND) to high voltage (trace1)
32 Terminal lines, cont. Add a second terminal lines for T3 Starting point is: 2, , Delta Z =Hit: Enter, Enter, Finish.Now, the Port1 is defined with 2 terminal lines named: T1, T3Do same thing to define Port2 with terminal lines of T2 and T4. (Note, Port2 is on plane location x=0 )
33 Assign BoundaryAssign radiation boundary on external surface of airbox.Click: Edit -> Select -> FaceHold down CTRL key, and select the external face of air1. Hold the ALT key to rotate the object to select facesClick: HFSS -> Boundary -> Assign -> Radiation. Hit Enter.In project window, click boundary -> RAD1, the radiation boundary shows on drawing windowDo the similar boundary assignment for air2
34 Boundary Assignment, cont. Now assign a radiation boundary on all external faces of FR4 material (faces on the outside)Don’t assign boundary on any metal objectsDon’t assign boundary on internal facesSometimes, it is easy to click one face and assign one boundary. ( Click multiple faces and assign one boundary is also OK)
35 Boundary overlap warning message If you run the validation check, there will be warning messages regarding the boundaries. It is because waveport1 assignment overlaps with radiation boundary. In this case, the port always has higher priority to overwrite the boundary.
36 Solution setupClick: HFSS-> Analysis Setup -> Add Solution SetupThe Solution setup window will pop up.We want to solve at 1 Ghz. Change the number of Passes: 5Change the Max Delta S: 0.01Click OK to accept default for rest of the settings.
37 Setup another solution Now, setup a sweep under first solutionClick: HFSS -> Analysis Setup -> Add Sweep. Click OK to pick setup1Edit Sweep window popupChange Sweep type: fastChange Sweep size: 0.5 GhzClick OK
38 Simulation! Click: HFSS -> Analyze Wait 15 min for this small simulation.
39 Simulation Results What simulation results can be found? S, Y, Z parameters, impedance matrixPlotting of above matrixE, H fields inside the structureCurrent density of structureNear & Far field radiations
40 S parameter Click: HFSS -> Results -> Solution Data Click on tab: Matrix DataSolution Data window pops up. It shows the S parameter matrix.To show data for all frequencies, click: All Freqs.This table gives you data for point analysis. For a general AC analysis, a plot is a better way
41 Plot of S11 Click: HFSS -> Results -> Create Report Change display type: Smith ChartPick Report Type: Terminal S parameters. Press OKPick Quantity: first entry, this is S11.Double Click this entry (trace appears at top)Click Done
43 Plot S21 Click: HFSS -> Results -> Create Report Set Display Type: Rectangular PlotClick: OKAt Plot window, select quantity: waveport T2, T1. This is the S21At function sub-window, select: dB. This will plot the magnitude of S21 in dBDouble Click (put entry at top)Click: Done
46 Homework Plot S31 Magnitude in dB (near end of cross talk) Find S31, S41 at 1Ghz.Plot Electric field that generated by via. Hint: Use HFSS -> Field -> Plot Field -> E Mag. Plot the E mag on the face of FR4_1 (center layer face)Do an animation for above E – field.
47 Project 1Compare the T-lines pass via with a typical micro strip. ( no via )Do the same simulation to find the difference on return loss, insertion loss and cross talkSuggest what is the cause of those differencesHow to improve it? Suggestions?Show the improved result on simulation
48 Project 2 Do the same thing as project 1 for a strip line. Copper 1 OZ 1.4FR4 DK = 4.11Copper 1OZSig5 mil / 10 mil spaceFR4DK = 4.152copper 1 OZGND4734Copper 1Oz 1.4
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