The Quarter-wave stub
The Quarter-wave stub can be used for many purposes. If it
is left with an open end it can be used as a notch filter to attenuate certain
frequencies. A quarter wave length of a transmission line can also be used as an
impedance transformer, to know more about the Quarter-wave impedance
The bandwidth of a quarter-wave notch filter is about 20 % (i.e. center frequency +/- 10 %).
Be aware of the fact that the Quarter-wave notch filter will not only attenuate the design frequency and the frequency band around the design frequency, but it will also attenuate the frequency band around the odd harmonics of the design frequency.
This page was last updated 21.12.14