question about stub matching

It is important to keep the total stub length as short as possible, if wider bandwidths are required.

Every time you add a half wavelength to the stub length the reactance of the stub comes back to the same value.

It is good design practice to make stubs in the range 0 to 0.5 wavelengths long. However, this may require an impractically short stub, so then one can make the stub just a little over 0.5 wavelengths.

Re-check here...

http://personal.ee.surrey.ac.uk/Pers...ies/stubs.html

How looks a 0 wavelength stub?

It is a theoretical value for high-frequency applications. ( > 60 GHz applications ).

The same way you mention a pulse (infitinitely small in time) in communications while you always have a certain time for it in real life in pulse generators.

does it somehow affect the resonant frequency if the stub too short?

" How Long is Too Long? A Via Stub Electrical Performance Study "

http://www.endicottinterconnect.com/...gnCon_2009.pdf