A frequency-tunable microwave band-pass filter, comprising at least one resonator, - each resonator comprising: * a cavity having a conducting wall that is substantially cylindrical along an axis Z, having a height H, with a position z along said axis Z being shown on an abscissa z between 0 and H, and being at least partly closed at two ends; and * at least one dielectric element disposed inside said cavity; - said resonator resonating in a mode in which two perpendicular polarisations (Px, Py) respectively have distributions of the electromagnetic field in said cavity that are derived from each other via a 90° rotation; - said mode having, in said cavity, N electric field maxima and N+1 electric field minima substantially located in a plane perpendicular to said axis Z, with the two ends of the cylinder respectively located on the abscissa z=0 and z=H corresponding to electric field minima, with a successive minima and maxima being separated by a separation distance H/2N, characterised in that it comprises: - rotation means adapted to set said element into rotation along an axis R that is substantially perpendicular to said axis Z between at least one first and one second position; - said element comprising at least one first end so that: * in a first position, said element is substantially disposed in a plane perpendicular to said axis Z and the centre of said first end is disposed at a height in said cavity that substantially corresponds to an electric field minima; * in a second position, said element is substantially parallel to Z and said first end is disposed in a plane that corresponds to an electric field maxima to the nearest +/- 30%. - each resonator comprising: * a cavity having a conducting wall that is substantially cylindrical along an axis Z, having a height H, with a position z along said axis Z being shown on an abscissa z between 0 and H, and being at least partly closed at two ends; and * at least one dielectric element disposed inside said cavity; * a cavity having a conducting wall that is substantially cylindrical along an axis Z, having a height H, with a position z along said axis Z being shown on an abscissa z between 0 and H, and being at least partly closed at two ends; and * at least one dielectric element disposed inside said cavity; - said resonator resonating in a mode in which two perpendicular polarisations (Px, Py) respectively have distributions of the electromagnetic field in said cavity that are derived from each other via a 90° rotation; - said mode having, in said cavity, N electric field maxima and N+1 electric field minima substantially located in a plane perpendicular to said axis Z, with the two ends of the cylinder respectively located on the abscissa z=0 and z=H corresponding to electric field minima, with a successive minima and maxima being separated by a separation distance H/2N, - rotation means adapted to set said element into rotation along an axis R that is substantially perpendicular to said axis Z between at least one first and one second position; - said element comprising at least one first end so that: * in a first position, said element is substantially disposed in a plane perpendicular to said axis Z and the centre of said first end is disposed at a height in said cavity that substantially corresponds to an electric field minima; * in a second position, said element is substantially parallel to Z and said first end is disposed in a plane that corresponds to an electric field maxima to the nearest +/- 30%. * in a first position, said element is substantially disposed in a plane perpendicular to said axis Z and the centre of said first end is disposed at a height in said cavity that substantially corresponds to an electric field minima; * in a second position, said element is substantially parallel to Z and said first end is disposed in a plane that corresponds to an electric field maxima to the nearest +/- 30%.