SMT Components on Microstrip

If a microstrip line is supposed to have a certain electrical length, but must be divided by an SMT component such as a DC blocking capacitor, does the length of the line need to be compensated (shortened) because of the gap placed in the line for the SMT part?

Any help would be appreciated, thanks
-Brandon

Hello Brandon,


There are couple of options...
Se in the Picture 1 Microstripline Length-I, say suppose it has length of 27.3mm
in the orginal trace , afte reducing the length say 17 mm it does not change the
Impedace it only changes loss & phase properties....
So use TXline Calculator freely available at AWR website to understand the feect..

OR use any RF simulation tools such as Microwave Office to study the effect on the design performance...


---manju---

I agree, the best thing would be to get a good model for the smt part and insert it into the line with a microwave analysis program.

If you were at a very low frequency, perhaps 100 MHz, I would not worry about it and just assume the length was the same with or without the part. If I was up at 3 GHz, I would HAVE TO analyze it, or the circuit would probably not work at all!

And I'll plug Modelithics again. Take a look at the app-notes to understand what effects they are modeling for SMT parts.

http://www.modelithics.com/