How to calculate microstrip gap capacitance?

[Terminator3]

I read that if gap is large, then effect of capacitor can be ignored. But to understand quantities i want to know approximate capacitance depending on gap size. For example, for 50Ohm line with gap size of 0.1, 0.2, 0.3 mm etc.. I found something for coupled lines, but it is unclear how to use it for simplier gap

 

[tony_lth]

In AWR, you can set the gap and simulated the different gaps and then you can reduct the cap capcitance.

 

[ferdows]

the formula for gaps was presented in many microstrip book by Bahl and others

 

[biff44]

a proper model for a gap is a series capacitance, with shunt capacitances on either side. The shunt capacitances become important in some cases.