Simulating Self inductance value of a microstrip trace

[viperpaki007]

I want to simulate inductance of a microstrip trace over a ground plane in an EM software like FastHenry. Is it necessary for me to define a return current path in simulations and connect the ground plane with microstrip trace, for estimating the inductance?

 

[maxwellian]

You can't have inductance without at least some implied return current path. However, there are software tools that will build in the ground plane assumption for you. There are a number of free transmission line calculators out there, like AppCAD that can do that for you. I think FastHenry will do it, and Sonnet Lite is another one that will give you Z-, Y- or S-parameters for a certain length of microstrip or stripline from which you can extract the equivalent inductance. I think they can extract the equivalent inductance as well, but you have to take care in setting up the problem so that your ports are neither too close together nor too far apart.

 

[viperpaki007]

Hi Maxwellian, Thanks for the answer. If i have to include the return ground path then i suppose the overall simulated inductance will include the inductance of ground trace as well. I just want to extract the inductance of microstrip trace. How can i do that?

 

[volker@muehlhaus]

If i have to include the return ground path then i suppose the overall simulated inductance will include the inductance of ground trace as well.

Correct. And it also includes the siginificant mutual inductance between microstrip and ground.

I just want to extract the inductance of microstrip trace. How can i do that?

You could do that with EM tools like FastHenry, but that value has not much practical meaning. The ground below will change the effective inductance by a large amount, due to the mutual coupling.

 

[FvM]

Perhaps you should first clarify the exact problem. A microstrip doesn't by definition exist without a ground plane. It's inductance can't be separeted into "trace" and "ground plane".

 

[viperpaki007]

Thanks for the help. Things are more clear to me now