The present invention relates to a band rejection filter. The band rejection filter includes a first signal transmission channel called a direct channel and a second signal transmission channel called a secondary channel. The direct channel and the secondary channel being designed to introduce at a first rejection frequency a phase difference of 180° between the signal circulating via the direct channel and the signal circulating via the secondary channel. Additionally, the secondary channel includes a filtering element for which the cut-off frequency is different from the first rejection frequency in a way to create a second rejection frequency.