Hi,
currently I am doing package simulation using EMPro 2009. The structure has 3 layers, the underlying two are the
same ceramic material, in between is the gold conducting sheet. On the bottom side of the lowest layer, there are
four sheet type Au electrodes (port 1 and port 2 being hot, port 3 and 4 as GND).
What I wanted to do is simulation of this package and get the S parameters. Then, export the S parameters file to
other design software, like Ansoft Designer, link the S-para file to the block, do the simulation in Ansoft designer,
with port 1 and port 2 both 50 ohm terminated.
My simple questions are as follows,
1)Simulations->New FEM Simulation->Mesh/Convergence Properties Setting
In EMPro, for FEM simulation, in the Mesh/Convergence Properties tap setting, in the advanced tap, in the bottom, there is one option, "Merge objects with same material". I wonder what is the advantage of this option? What I guess is that this will speed up the simulation. I am not sure whether this option can be applied to my simulation as described above?
2)Simulation Domain->Boundary Condition Setting
In EMPro, main window left column, there is the Simulation Domain setting, for the Boundary Condition, I am not sure whether I should set the lower boundary of Z to PEC(perfect electrical conductor). I noticed that as in the EMPro offered example "microstrip line", the lower boundary Z is set to PEC since it is used as the GND. In my case, only part of the lower boundary of Z is GND, therefore I set the lower boundary Z to Absorbing.
3)Cicuit components/Ports setting
There are two options, one is the waveguide port, the other is the feed (line source) port. In my case, I used the line source, I am not quite sure whether I am correct.
4)Simulation Domain->FEM Padding setting
I set the padding to be 1mm greater than the package in X, Y, Z lower and upper dimensions. My question is that whether the S-parameters would be affected by the padding setting? Personally I think it will not be affected.
Sorry for making it so long. Really appreciate your help.
With my best wishes,
currently I am doing package simulation using EMPro 2009. The structure has 3 layers, the underlying two are the
same ceramic material, in between is the gold conducting sheet. On the bottom side of the lowest layer, there are
four sheet type Au electrodes (port 1 and port 2 being hot, port 3 and 4 as GND).
What I wanted to do is simulation of this package and get the S parameters. Then, export the S parameters file to
other design software, like Ansoft Designer, link the S-para file to the block, do the simulation in Ansoft designer,
with port 1 and port 2 both 50 ohm terminated.
My simple questions are as follows,
1)Simulations->New FEM Simulation->Mesh/Convergence Properties Setting
In EMPro, for FEM simulation, in the Mesh/Convergence Properties tap setting, in the advanced tap, in the bottom, there is one option, "Merge objects with same material". I wonder what is the advantage of this option? What I guess is that this will speed up the simulation. I am not sure whether this option can be applied to my simulation as described above?
2)Simulation Domain->Boundary Condition Setting
In EMPro, main window left column, there is the Simulation Domain setting, for the Boundary Condition, I am not sure whether I should set the lower boundary of Z to PEC(perfect electrical conductor). I noticed that as in the EMPro offered example "microstrip line", the lower boundary Z is set to PEC since it is used as the GND. In my case, only part of the lower boundary of Z is GND, therefore I set the lower boundary Z to Absorbing.
3)Cicuit components/Ports setting
There are two options, one is the waveguide port, the other is the feed (line source) port. In my case, I used the line source, I am not quite sure whether I am correct.
4)Simulation Domain->FEM Padding setting
I set the padding to be 1mm greater than the package in X, Y, Z lower and upper dimensions. My question is that whether the S-parameters would be affected by the padding setting? Personally I think it will not be affected.
Sorry for making it so long. Really appreciate your help.
With my best wishes,
Merge objects is to merge objects overlapped or touching each other. By merging objects, the number of vertices of combined object might be smaller than the total of individual objects, which may result in a faster simulation since FEM mesher starts from the given number of object's vertices. As an example, you can imagine two rectangles (one smaller that the other) overlapped each other. As two objects, the total number of vertices is 10 including two additional vertices added by overlapped rectangles. With the merge, it becomes 8, saving 2 vertices. Therefore the size of matrix may be smaller.
2. Lower boundary
In your case, you shouldn't set the lower boundary to PEC since it will make everything short circuited. For this ceramic package, is it mounted on a PCB or similar kind? If so, it would be better to use the lower side of PCB as ground, means you can set it to PEC. If not, your reference ground pin should be on port 3 and 4, them the lower will be ABC (Absorbing boundary condition) with some padding distance.
3. Ports (Waveguide or Voltage/Feed)
Generally speaking, you should be using the waveguide port as much as possible since it is calibrated, means less parasitics with the port itself. However in your case, it would be better to use the voltage source since the pads may not be on the boundary surfaces. In this case, please use sheet ports which comes with less parasitics than the voltage source.
4. Size of padding
In fact, the size of padding will affect the s-parameter results. As a rule of thumb, you should have enough padding to decouple any boundary conditions to your design. Simply you can use 8~10 times rule. For example, if the substrate thickness is 100 mils, then put 800 mil for the padding.
Hope this helps.
HeeSoo LEE