effect of ohmic contact of microstrip pcb

[moreho]

what happens if i use a metal carrier that have about 2-3 ohm surface resistance (not ~zero) to fabricate a microstrip board on it.

it seems that one of bad effect will appear on signal loss...

can anyone describe it...

 

[FvM]

What do you understand as "surface resistance"? Sheet resistance of the metal layer? How do you "fabricate" the microstrip? Can you show a cross section?

If you have a clearly defined geometry and material specification, you can simulate the setup with an EM tool.

 

[moreho]

consider a multimeter that we put the probes slightly on the surface of metal carrier without any pressure.
if the carrier has a good finishing, or it is a pure and good metal, the resistance measured by multimeter is a number for example under 1 ohm.
but otherwise, it may shown a number also about a few decades of ohms that is not constant and depend on the position of probes, the measured resistance will change rapidly.
if this carrier used to montage a board, the ground of ms line may degrade in quality and will affect in insertion loss.

i can simulate a ground with bad conductivity and see the results|! but i want to know in real world, any experience, any idea that may happen for other ones.

any idea,,, plz
thanks..

 

[vahidqc]

when you use full-wave simulation for any structure (your case is a simple one), the result of your simulation should be like the result of fabricated one. this is achievable when you define all elements(such as transmission line, inductor, capacitance, I/O connectors and etc) correctly in your structure.
for a transmission line (TL) in the low frequency( e.g. up to several GHz), this is usual that for TL is considered a real conductivity. in fact, it shows the amount of ohm of the TL.
so, if you define a correct conductivity for your metal carrier (or TL), the result of your simulation and experiment must be the same.

I hope these words be helpful.

 

[FvM]

A thin dielectric layer, e.g metal oxide, between metal and dielectricum won't affect the microstrip properties. A problem can be with semiconducting layers like copper or silver sulphide. So you'll need to ask for the exact material properties. The ohmeter test is probably not significant.