impedance coplanar stripline
I am simulating a Coplanar Strip Line on ground plane. I m using waveport at one end with 2 modes....and differntial port with reference impedance of 100Ω in differential mode and 25Ω as common mode reference. The waveport is normalized to 50Ω impedance. I am connecting a lumped element say a resistance of 100 Ω at other end of the coplanar strip line. I am defining it by a rectangle of lumped RLC boundary.
I am trying to calculate the ZL in my case (should be ≈100Ω), by using standard transmission line equations. I am considering the complex γ, for my calculations but ..... I do not get the correct approximation.....for load impedance. I am not able to validate my results....can soem one look into my problem and comment on it...
any help is appreciated.....
Hi maverick,
I'd like to help you but I think I didn't really understand your question; could you share your project to let me have a look at it?
Antonio
[quote="maverick09"]Hi,
I am simulating a Coplanar Strip Line on ground plane. I m using waveport at one end with 2 modes....and differntial port with reference impedance of 100Ω in differential mode and 25Ω as common mode reference. The waveport is normalized to 50Ω impedance. I am connecting a lumped element say a resistance of 100 Ω at other end of the coplanar strip line. I am defining it by a rectangle of lumped RLC boundary.
quote]
hi, maybe you can choose HFSS->solution type->driven terminal, then, you can assign waveport, you will see that differential mode and common mode. hope help for you!~
Edmund
hi,
here it is....
Your resistor was not snapped to the top of your traces. After fixing that I think the input impedance is better. Zcomm is good but Zdiff has some VSWR.
but why do you think iam not getting teh right value of the load impedance from the calculations?....i want to validate my design.....how can it de done?
In order to get Zdiff=25 ohms I believe you must tie the center of the resistor to the ground plane. To model this you must have two 50 ohm resistors in series, with the center point grounded.
Here are some tips I have from looking at the circuit:
1) Instead of using thick conductors, start with rectangles and assign PEC boundries. Once you get things working then add thickness.
2) Don't put the resistor at the edge of the box where it touches a boundry. End effects of the CPW will not be computed correctly.
3) De-embed your port into the box so port discontinuities are removed from your results. You should be able to de-embed almost to the resistor and remove the transmission line effects to verify your result.
4) Don't snap your port integration line to the center of a thick conductor. I don't think a integration line can be tangent to a conductor.
5) You can assign the whole box as one radiation boundry, you don't need a seperate one for each face.
6) Assign transparency of 0.8 to all objects so they are easier to manipulate.
7) Your solution frequency must be higher than your sweep or else the adaptive meshing will not be accurate. Your mesh does look good though.
hi,
I am attaching a load impedance of say 25 Ω;, at one end of the coplanar strip lines.
I simulate the structure......I take S(waveport1:diff1,waveport1:diff1),then I calculate Γ, then input impedance Zin. Similarly I calculate the value of my short circuit impednace and open circuit impedance. Then I am using these values to obtain my ZL (actual load impedance of 25 Ω)......My question is why I cannot get the value of 25 Ω; at the other end? ....
Also could you please explain to me how can I tie the resistors to ground......
Also I am trying to simulate my structure by placing the resistor near to the waveport....(rather than other end)......