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1、1,Signal Integrity Lab 2 Ansoft High Frequency Structure Simulator (HFSS),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
2、 inch,3,Stack up,1 mil = 0.001 inch, Signal trace width = 5 mil Signal to signal space = 20 mil,4,Configuration,Start HFSS Save file Insert HFSS design Setup solution type: Driven Terminal Setup grid to 0.1 inch,5,Structure Design,Draw a BOX at: 0, 0, 0, size: 2, 2, 0.005 inch. Assign material: FR4_
3、epoxy. Set transparent: 0.7 Rename it: FR4_1 Draw 2nd BOX at 0, 0, 0.005, size: 2, 2, 0.0014 inch. Assign material: Copper. Set transparent: 0.7 Rename it: GND1 Draw 3rd BOX at 0, 0, 0.0064, size: 2, 2, 0.047 inch. Assign material: FR4_epoxy. Set transparent: 0.7 Rename it: FR4_2 Select GND1 by clic
4、king 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, 0.0534 as new origin. This moves GND2 to upper layer,6,Stack up Design,
5、Do the same thing to copy FR4_1 and make it FR4_3. Put new origin as: 0, 0, 0.0548 Now the stack up is ready. It has two ground layers and 3 FR4 layers. Grey color is for FR4 and Blue is for GND,Side view of PCB stackup,7,Add signal trace,Draw a BOX at: 0, 1, 0.0598, size: 1.005, 0.005, 0.0014 inch
6、Rename it: Trace1, Assign Material: Copper. Change the color to: RED Copy Trace1, and Paste it. Now you got trace2. Change trace2s 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 o
7、ther by 10mil. In order to see both traces, you need to set transparent property of all drawing to be 0.7,8,9,What is via and anti-via,What is via & anti-via What does via do? What does anti-via do?,10,Via: vertical connection between layers Barrel: conductive cylinder filling the drilled hole Pad:
8、connects the barrel to the component/plane/trace Antipad: clearance hole between via and no-connect metal layer,Barrel,Pad,Via pad does not contact plane; void is the anti-pad,Trace connected to pad on layer 1.,11,A Via might: Connect metal planes of the same potential (e.g., all ground planes condu
9、ctively attached) Carry a signal from a trace on one layer to another (e.g., every data signal must get from the silicon bump down to the motherboardand possibly through the motherboard!) Connect components (such as a capacitor) to a signal trace or a voltage plane.,12,Add via and anti-via,Click the
10、 cylinder icon, draw a cylinder between two traces. Change the current position to: 1, 1.0025, 0 inch, radius: 0.005 and height: 0.0598 inch. Assign the material: copper. Change the color: RED Rename it: via1 Do another cylinder (10mil radius), assign material: Fr4_epoxy, rename it: anti_via1 Two cy
11、linders overlap and center at same location. - this will cause a problem and confuse the software! Why?,13,Bolean function,The 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: FR
12、4_1, FR4_2, FR4_3, GND1, GND2, anti_via1 This selects the 6 items above to perform a Boolean function Click: 3D Modeler - Boolean - Subtract,14,Bolean Function - subtract,Subtract window pops up. Move, FR4_1, FR4_2, FR4_3, GND1, GND2 to Blank Parts window Move anti_via1 to Tool Parts window Select “
13、Clone tool objects before subtracting” Why? Click “OK”,15,View - Visibility,After subtraction, graphic verification is hard since all the components overlap each other. (visibility setting can solve this problem) Click: View - visibility Visibility window pops up. Turn off the visibility on all FR4
14、and anti_via1 It is verified that via passed through two layers of ground without touching it,16,Question.,The overlap issue between FR4, GND and anti-via is solved. Theres another overlap error. Which one?,17,Overlap problem 2,Theres overlap between anti-via and via. Use Boolean subtraction functio
15、n, subtract via from the anti-via. Dont forgot to “clone” the via Use the visibility command to verify that anti_via1 has a hole in the center.,18,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 int
16、o 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 material Your field solution is more accurate and process is faster after you unite the similar items If you want to un-do the “unite”, go to command history wind
17、ow and delete the “unite” under FR4_1 Do the same thing to unite: trace1, trace2, via,19,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 location of trace1. (they overlap each other) Click and s
18、elect: trace3 Click: Edit arrange - move Use 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.,20,Create 2nd trace, cont.,Now, the sub window pops up. Make sure the
19、 move vector is 0, 0.02, 0 This makes the 2nd trace 20mil away from 1st trace. What is the air gap size between the traces?,21,2nd Anti-via,Create an anti-via for the 2nd trace. The center location should be 0, 1.023, 0 Review slide 10 for creating an anti-via Rename the new item: anti_via2 Theres a
20、n 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.,22,Structure with 2 traces,23,Add Air Box,Need to add “Air” boxes on top & bottom of PCB. Why? Draw a box at 0
21、,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 setting of 0.95 Air boxes overlap with trace1 and trace3. Use the Boolean function to do the subtraction,24,Structure Desig
22、n is completed,25,View at different angle,Click: View - Modify Attribute - Orientation You 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 picture Select the FR4_1 item, make the transparent property: 0,26,27,
23、Port & Terminals Sample,28,Port & terminal,1,2,3,4,Terminals,Port is a 2D rectangular area Terminals are each end of traces Port contains terminals,29,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, 0
24、.005. Y size: 0.05, Z size: -0.05 Set transparency: 0.8 Rename: Port1 Do another 2D rectangle at: 0, 0.988, 0.0548. Y size: 0.05, Z size: 0.05 See picture next slide.,30,31,Terminals,Set the view at: front view Select by clicking: Port1 Click: HFSS - Excitation - Assign - Wave Port Click: Next , the
25、 Wave Port terminal window pops up. Set: Number of Terminals = 2, Click: update Change the name of 2nd Terminal line to T3. At T1 Terminal Line cell, click & select: New Line Use coordinate system to key in terminal lines,32,Terminal Lines,The terminal lines have to be on the Port1 plane. It has to
26、go from GND1 to Trace1 It 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,33,Terminal lines, cont.,At co
27、ordinate system, enter: 2.0, 1.0025, 0.005 inch for xyz. Hit: Enter Enter: 0, 0, -0.005 for Delta x, y, z, hit Enter Now 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),34,Terminal
28、lines, cont.,Add a second terminal lines for T3 Starting point is: 2, 1.0225, 0.005. Delta Z = -0.005 Hit: Enter, Enter, Finish. Now, the Port1 is defined with 2 terminal lines named: T1, T3 Do same thing to define Port2 with terminal lines of T2 and T4. (Note, Port2 is on plane location x=0 ),35,As
29、sign Boundary,Assign radiation boundary on external surface of airbox. Click: Edit - Select - Face Hold down CTRL key, and select the external face of air1. Hold the ALT key to rotate the object to select faces Click: HFSS - Boundary - Assign - Radiation. Hit Enter. In project window, click boundary
30、 - RAD1, the radiation boundary shows on drawing window Do the similar boundary assignment for air2,36,Boundary Assignment, cont.,Now assign a radiation boundary on all external faces of FR4 material (faces on the outside) Dont assign boundary on any metal objects Dont assign boundary on internal fa
31、ces Sometimes, it is easy to click one face and assign one boundary. ( Click multiple faces and assign one boundary is also OK),37,Boundary overlap warning message,If you run the validation check, there will be warning messages regarding the boundaries. It is because waveport1 assignment overlaps wi
32、th radiation boundary. In this case, the port always has higher priority to overwrite the boundary.,38,Solution setup,Click: HFSS- Analysis Setup - Add Solution Setup The Solution setup window will pop up. We want to solve at 1 Ghz. Change the number of Passes: 5 Change the Max Delta S: 0.01 Click O
33、K to accept default for rest of the settings.,39,Setup another solution,Now, setup a sweep under first solution Click: HFSS - Analysis Setup - Add Sweep. Click OK to pick setup1 Edit Sweep window popup Change Sweep type: fast Change Sweep size: 0.5 Ghz Click OK,40,Simulation!,Click: HFSS - Analyze W
34、ait 15 min for this small simulation.,41,Simulation Results,What simulation results can be found? S, Y, Z parameters, impedance matrix Plotting of above matrix E, H fields inside the structure Current density of structure Near & Far field radiations,42,S parameter,Click: HFSS - Results - Solution Da
35、ta Click on tab: Matrix Data Solution 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,43,Plot of S11,Click: HFSS - Results - Create Report Change
36、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,44,S11 on Smith Chart,45,Plot S21,Click: HFSS - Results - Create Report Set Display Type: Rectangular Plot Click: OK At Plot
37、window, select quantity: waveport T2, T1. This is the S21 At function sub-window, select: dB. This will plot the magnitude of S21 in dB Double Click (put entry at top) Click: Done,46,S21 Magnitude in dB,47,S21, Real & Image Part,48,Homework,Plot S31 Magnitude in dB (near end of cross talk) Find S31,
38、 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.,49,Project 1,Compare 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 talk Suggest what is the cause of those differences How to improve it? Suggestions? Show the improved result on simulation,50,Project 2,Do the same thing as project 1 for a strip line.,