This beam passes through an input cavity resonator. Hansen proposed replacing the coil with a cavity resonator. One option is to measure the resonance frequency of a cavity resonator. A basic component of waveguide filters is the cavity resonator. Following this, the next step is the subwavelength cavity resonator. A reverberation chamber is a cavity resonator with a high Q factor. The beam first passes through the "buncher" cavity resonator, through grids attached to each side. A cavity resonator is an empty (or sometimes dielectric-filled) space surrounded by conducting walls.