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1、1,Signal Integrity,Software name: Ansoft HFSS 9,2,What is HFSS,High Frequency Structure Simulator Uses Finite Element Method to solve EM problems Frequency Domain Solution Full wave Solver,3,4,Different Methods in Electromagnetic Analysis,MOM,5,What is Finite Element Method (FEM) Software?,FEM softw
2、are is a design tool for engineers and physicists, utilizing rapid computations to solve large problems insoluble by analytical, closed-form expressions The “Finite Element Method” involves subdividing a large problem into individually simple constituent units which are each soluble via direct analy
3、tical methods, then reassembling the solution for the entire problem space as a matrix of simultaneous equations FEM software can solve mechanical (stress, strain, vibration), aerodynamic or fluid flow, thermal, or electromagnetic problems,6,FEM Problem Constraints,Geometry can be arbitrary and 3-di
4、mensional Model subdivision is generally accomplished by use of tetrahedral or hexahedral (brick) elements which are defined to fill any arbitrary 3D volume Boundary Conditions (internal and external) can be varied to account for different characteristics, symmetry planes, etc. Size constraints are
5、predominantly set by available memory and disk space for storage and solution of the problem matrix Solution is created in the frequency domain, assuming steady-state behavior,7,Example of Adaptive meshing,Waveguide Filter at right (symmetry along top face) shows effect of mesh adaptation. The regio
6、n between posts has a denser mesh, due to the superposition of reflected energy found in the solution process.,Post,Post,8,When is an FEM solver appropriate for Electromagnetic Problems (Lower Bound)?,/100,0,Use a Quasi-Static Solver,Use a FEM Full-Wave Solver,Problem Scale,Example: Finding Signal I
7、ntegrity impacts of a Via in the signal path,/10,(OVERLAP),Example: Coax to WG Transformer,When the Electrical Length (in wavelengths) requires phase consideration /10 is a guideline; there are exceptions When radiation from the device must be considered When S-Parameters are the desired output When
8、 lossy dielectric materials have significant effects,9,Some Typical High-Frequency Electromagnetic Applications,Waveguide Components,Antenna,RF Integrated Circuits,EMC,10,Example 1: Eigenmode Problem,Find the resonant frequencies of a perfect metal box filled with “glass”. The box size is 3x2x2 inch
9、. Draw the electric field inside the box at those resonant frequencies.,11,Ansoft HFSS Project Flow,Configuration,Drawing,Boundary,Source Excitation,Solution Setup,Solving,Analyze Data Plot,12,Configuration,Click HFSS 9 to start the problem Click: File - Save As - filename Click: Project - Insert HF
10、SS Design Now, HFSS design interface has 6 sub-windows: project window, property window, drawing window, history window, message window and execution window,13,14,Configuration cont.,Click: HFSS - Solution type, Pop up window shows three types Pick the Eigenmode,15,Configuration,Click: Tool - Option
11、 - General Option Option window pop up. Select Default Units tab Change the length to: “inch”,16,Configuration,Click: View - Grid Setting Grid setting screen pops up Select grid size as 1 inch,17,Structure Drawing,Click: Draw - Box ( You can also click on the draw box toolbar) On Drawing window, fir
12、st click will set the start point, second click will set the base end point, and the third click will set the height of box. ( draw a 3 inch x 2 inch x 2 inch box) The property window will pop up. In the command tap, make sure the Position is at 0, 0, 0. The x-size, y-size and z-size is what you wan
13、ted. In the Attribute tab, change the material to “glass”. Change the Transparency to be “0.8”,18,Drawing,Here is the picture of what you get. You can always change the item properties by clicking the item, and modifying them at property window,19,Hint,Hold the keyboard “Shift” and drag the mouse, y
14、ou can PAN the drawing Hold the keyboard “ALT” and drag the mouse, you can rotate the drawing Hold the “Shift” and “ALT” and drag the mouse, you can zoom the drawing,20,Boundary,Click Selection toolbar. See picture. Change the Selection from Object to Face Now, click the face of box. Hold down the C
15、TRL key and click face to add all 6 faces as selected. You may need to rotate the BOX so you can select all 6 faces. In menu, click HFSS - Boundaries - Assign - Perfect E. This assigns perfect Electric conductor on all 6 faces of box,21,Hint,You can also set the selection box as “Object”, and select
16、 the whole box to assign the boundary. In that case, the software will assign same type of boundary on every surface of this objective You can also select one face assigned as “Perfect E” and another face assigned as “Radiation” or any other type of boundary.,22,Question,If the object is already a m
17、etal, you dont need to assign the boundary on that face. Why? For Eigenmode solution, you must assign Perfect E or Finite conductor on all face. Why?,23,Source Excitation,For eigenmode solution, you dont need to add source excitation. The software will automatically add the EM excitation inside the
18、boundary. For driven modal or driven terminal projects, you DO need to add source excitation. And, it is very important you do it right. ( more on later),24,Solution Setup,The structure is ready to simulate. Click: HFSS - Validation check to see if theres any mistakes in drawing or boundary assignme
19、nts. Click: HFSS- Analysis Setup - Add Solution Setup,25,Solution Setup,The Solution setup window pops up. Change Minimum Frequency to: 1GHz Change Number of Modes to 5. ( find first 5 resonant frequencies) Change Maximum Number of Passes to 5 Click OK,26,Solution Setup 2,You can enter multiple solu
20、tion setups. This is useful and convenient when you are seeking for multiple answers. Go to Solution setup menu again, this time enter (1) Minimum Freq. 1GHz, (2) Number of Modes: 1, (3) Number of pass to 5. Now, you have two solutions in the project. If you check the project manager window, they ar
21、e called setup1 and setup2 under Analysis tab.,27,Run Simulation,Click: HFSS - Analyze Relax and wait. This project takes less than a couple minutes to simulate. Large projects will take more than 24 hours to simulate. Watch the “execute window” or “message window” for any errors or warnings.,28,Sol
22、ution Data,Click: HFSS - Results - Solution Data Click Eigenmode Data tab. It shows the results of first 5 modes Question: What is first resonant frequency? What is 2nd Freq? What is the 3rd ?,29,EM Plot,Click the BOX1 on drawing window Plot the Electric field inside the box by clicking: HFSS - Fiel
23、ds - Plot Fields - Mag_E Field plot window will pop up.,30,EM plot cont.,Select Solution Setup2 Last Adaptive Only plot the first resonant frequency Select “BOX1” at In Volume sub-window. Select “Mag_E” at Quantity sub-window. Click: Done,31,E Field Plots,32,Plot Animation,Click: HFSS - Field - Animate Select: 18 frames (steps) Click: OK,33,4th Resonant Plot,34,4th Resonant, Vector Plot,35,Homework,Design a cylinder cavity Base Radius = 2 inch Height = 5 inch Inside material = FR4_eposy Find: first 5 resonant frequencies Plot: Mag_E field for 5th resonant,