  In particle accelerator components, parasitic resonances must be reduced
because they heat up the equipment and cause beam instabilities. In this paper,
a method for designing and characterizing Higher Order Mode (HOM) couplers for
reducing such resonances in a broad bandwidth is proposed. A case study is
considered for a specific component, called QuattroTank, showing geometrical
discontinuities and thus causing significant electro-magnetic resonances.
Results of numerical simulation and experimental emulation prove the capability
of the proposed method to reduce the peaks and the $Q-factor of the resonances.
