Tutorials about CPW design on a PCB

Hi

I am a beginner in the design of PCB's. I normal design RF connectors.

So, I have a question regarding the use of CPW on a PCB. When I run my sim in HFSS I find the the impedance is not consistant thru the frequency range, i.e. it starts at 51 ohms and ends at 79 ohms at the high frequency. I read that there are some methods that are used to fix this problem but I have not found, anywhere that tells me what are these methods.

So, can anyone guide me to some tutorials on this subject.

Thanks

HFSS help has specific guidelines for Zo calculations. Look into that and the set up of wave ports relative to CPW lines. Your problem may go away. Search on Impedance calculation to find the sections.

when you use waveport, it will calculate the real port impedance. However, you can always normalize it to 50 ohm. You can use lumped port where you can pre-define the port impedance.

i met the same problem, but i guess it is normal since it is not exact TEM mode and dispersion.

Thanks for your comments but what I am trying to do is create a stable 50 ohms PC board design. When I look at the TDR it shows me that the board impedance is not 50 ohms and I need some advise on how the PCB designer's acomplish this. Do they use via's, or add capacitors, or ....