Coupled Lines -two microstrip lines running parallel on FR4

[arefeidi]

Coupled Lines

Hi,

I have to microstrip lines (length smaller than λ / 4) running parallel on FR4. The distance between them is about 2.5mm, frequency is about 1 GHz. Substrate thickness is about 400µm, width of each line about 1mm.

Am I right that there is about no coupling between them, so that I don't have to simulate with coupled lines?

 

[vfone]

Re: Coupled Lines

Theoretically you get coupling between lines placed at any distance, but lower coupling could be ignored.
Now depends how smaller than λ/4 is your line, to get insignificant coupling.
For example if the length is λ/8 for this spacing can get a coupling of 40dB.

 

[arefeidi]

Re: Coupled Lines

The length is not yet decided as I still have to figure out the right length to do the impedance matching - though it will be about λ/6 to λ/4 though as it looks.

30...40dB can be neglected in my case...so no need to take the coupling into account. Thanks!

 

[flyhigh]

Re: Coupled Lines

Hi

as a rule of thumb, you can consider two microstrip lines to be uncoupled if they are separated more then 5 line widths, so your lines can be considered coupled. The amount of coupling is related to electrical lengths. Not sure about the nature of the signals running on these lines, but my advice would be to be careful!

flyhigh