A basic concept behind how an RF filter works is impedance changes with frequency. The reason why an inductor would have a higher impedance at a higher frequency and a capacitor has a lower impedance at a higher frequency is due to the different ways these two components react to different frequencies. An RF filter uses this fact as a basis for creating transmission paths that will only allow frequencies within a certain range to be transmitted while blocking all other frequencies. Regardless of whether the RF filter is designed as low pass, high pass, bandpass or band-stop, every RF filter performs frequency selection by using the resonate structures of the RF filter. In this way, an RF filter cleans a signal prior to the signal being sent to the sensitive receiver circuits.