I am not sure exactly what you are describing, but the impedance of stubs changes with their electrical length, so if you change their length they appear to be open circuit, or short circuit, at a different frequency, so I would expect the positions of the zeros to change.

I see from a previous question that you do not seem to understand what a stub is. It is a transmission line that acts as a transformer to transform the impedance at one end to a usually different impedance at the other. The transformation ratio depends on the length of the stub measured in wavelengths in the transmission line. It will transform an open circuit to a short circuit over a quarter wavelength, and back to an open circuit in another quarter wavelength. In between it will appear as a capacitor or an inductor with a value depending on the line impedance and the electrical length. You need to read an introductory book on transmission lines.

Thank you Dr Malcolm very very much for such elaborate and nice explanation. I do understand it now.. Can you help me out if possible refer a book/journal on-"how change in electrical length effect the frequency of TZs"..Is there any relation/formula?? kindly guide. ...i am really thankful to you for kind reply..

ThanksRegards

Nitin

Look up transmission line on the internet. Look up transmission line stub, or transmission line choke.

OKK Sir. Thanks