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HFSS Tutorial 4: 20-dB Microstrip
Coupled Line
Goal: design a 20-dB microstrip coupled line operating at 2.42 Ghz. substrate thickness 1.6 mm and. Lessons learned:
- Wave port of microstrip lines.
- Wave port with 2 modes.
- Even-odd mode analysis. Initial size: , , ,.
- First, verify the microstrip line. Insert a New Design. Rename it to “50 Ohm Line”. Project->Insert HFSS Design
- Save it as tutorial File->Save as
- First we want to determine the adequate port size. From the
guideline of HFSS, make the port size.
- Create two rectangular boxes with the following parameters. a. Substrate: size ( ), position ( ). b. Air: size ( ), position ( ). Draw->Box
- Create three rectangular sheets with the following parameters. a. Feedline: size ( ), position ( ). b. Gound: size ( ), position ( ). c. Port: size ( ), position ( ). Set
- Assign Perfect-E Boundary to the feedline and ground.
- Assign Wave Port to the port surface.
- Add two solve-port-only simulation. One with “Maximum Delta ” set to 2% and one with 0.1%. Analysis->Add Solution Setup
- Add Interpolation Sweep from 1 GHz to 3 GHz. Step size 0.01. Setup1->Add Frequency Sweep
- Perform simulation. Check the mode field to see if it is the right mode. Check the mesh too. Sweep->Analyze
- Plot the propagation constant and. Check the convergence. It appears that “Maximum Delta ” must set to 0.1% to get better.
- Add Parametric Sweep for. Optimetrics->Add->Parametric Plot the propagation constant and. Use n as te sweep variable. It can be seen that convergence is reached after.
- Second, design the coupled line. Create the first part of the coupled line by modifying the size and position of the feedline..
set. Then, adjust the size of the substrate and air by setting and. Also set to reduce computation cost.
- Create the first feedline. Size ( ), position ( ).
- Use duplicate to reproduce the second line. Edit->Duplicate->Along Line Set “Total Number” to 2. Set “Vector” to ( ).
- Use duplicate again to reproduce the third and forth lines. Select the first and second lines. Edit->Duplicate->Along Line Set “Total Number” to 2. Set “Vector” to ( ).
- Use line to form the triangle connecting the coupled line and the first feedline. Draw->Line Set the position of the three points to ( ), ( ), ( ).
- Use duplicate and mirror to reproduce the second triangle. Edit->Duplicate->Mirror Set “Normal Position” to ( ).
- Select the two triangles and use duplicate and mirror to reproduce the third and fourth triangles. Edit->Duplicate->Mirror Set “Normal Position” to ( ).
- Set the port 1 size and position to Size: ( ). x -directed. Position ( ).
- Use duplicate to reproduce the second port. Edit->Duplicate->Along Line Set “Total Number” to 2. Set “Vector” to ( ).
- Use duplicate again to reproduce the third and forth ports.
1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3. Freq [GHz] -50. -40. -30. -20. -10. -0.
dB S Parameter (^) Curve Info dB(S(1,1)) Setup1 : Sweep dB(S(1,2)) Setup1 : Sweep dB(S(1,3)) Setup1 : Sweep dB(S(1,4)) Setup1 : Sweep 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3. Freq [GHz] -90. -88. -87. -86. an g_ de g( S( 1 ,^2 ))- an g_ de g( S( 1 , 4 )) [d eg ] S Parameter_ Curve Info ang_deg(S(1,2))-ang_deg(S(1,4)) Setup1 : Sweep Select the first and second ports. Edit->Duplicate->Along Line Set “Total Number” to 2. Set “Vector” to ( ).
- Assign PEC boundary to the lines.
- Assign wave port to all ports. Set de-embed length to.
- Perform a frequency sweep. Plot the S-parameters and to verify the results. Check the four port field to make sure they are in correct alignment.
