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Wierd S-Parameter results simulating C-Band PCB traces in CST Studio.
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Hi,
This is my first time posting question about CST microwave studio. I am having some issues with simulating a section of my PCB and have gone through a great deal of revisions to get even to this position; where the simulation goes through and actually gets processed. I have extended some of the traces and flushed out the conductor between the lumped elements, since I have a co-planar design. I have surrounded these small areas with a vacuum block element and removed any vias which intersect with the flow of the signal.
The issue that I am having is that my S-Parameter results are quite weird, my s41 is giving me -25 dB and my s21 is -12 dB, upon inspection it seems that an incredible amount of energy is being lost as the signal propagates through the board. This to me seems quite unreasonable as the traces are perfect copper conductors and are impedance matched with the respective dielectric below the copper. I am expecting maybe a 1 to 2 dB low through all the traces.
I am simulating by exciting only 1 discrete port, using the default library of excitation signals, simulating from 5.7 to 5.9 GHz and using 2.5 million mesh cells (mm) I believe resolving ports or resolution problems are no longer an issue. I set up an S-Parameter task, giving results in magnitude/phase and then clicking on update tasks.
Another thing to note is that when my 1D results come through, it says that my Input port has an impedance of 14 Ohms, even though I have set the impedance of all ports to be 50 Ohms and prior stage in CST reports the impedance of a signal on the top layer to be 49.3 Ohms. I feel that something is going fundamentally wrong either some setting that I have forget to select or some element of the pre simulation setup that I am missing.
If anybody reading this require the graphs or any further information please post below and I will send them over or update this post immediately. Any help is greatly appreciated.
Thank you, Jay.
This is my first time posting question about CST microwave studio. I am having some issues with simulating a section of my PCB and have gone through a great deal of revisions to get even to this position; where the simulation goes through and actually gets processed. I have extended some of the traces and flushed out the conductor between the lumped elements, since I have a co-planar design. I have surrounded these small areas with a vacuum block element and removed any vias which intersect with the flow of the signal.
The issue that I am having is that my S-Parameter results are quite weird, my s41 is giving me -25 dB and my s21 is -12 dB, upon inspection it seems that an incredible amount of energy is being lost as the signal propagates through the board. This to me seems quite unreasonable as the traces are perfect copper conductors and are impedance matched with the respective dielectric below the copper. I am expecting maybe a 1 to 2 dB low through all the traces.
I am simulating by exciting only 1 discrete port, using the default library of excitation signals, simulating from 5.7 to 5.9 GHz and using 2.5 million mesh cells (mm) I believe resolving ports or resolution problems are no longer an issue. I set up an S-Parameter task, giving results in magnitude/phase and then clicking on update tasks.
Another thing to note is that when my 1D results come through, it says that my Input port has an impedance of 14 Ohms, even though I have set the impedance of all ports to be 50 Ohms and prior stage in CST reports the impedance of a signal on the top layer to be 49.3 Ohms. I feel that something is going fundamentally wrong either some setting that I have forget to select or some element of the pre simulation setup that I am missing.
If anybody reading this require the graphs or any further information please post below and I will send them over or update this post immediately. Any help is greatly appreciated.
Thank you, Jay.
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