A stub is an open-circuited or short-circuited section of transmission
line. It can be a series stub or a parallel stub. It can be inductive,
capacitive, or resonant depending upon length. At a single frequency, a
stub can replace an inductor or capacitor and/or cause a change in
impedance, i.e. a change in the voltage to current ratio. (Not to be
confused with software stubs.)
--
73, Cecil http://www.qsl.net/w5dxp