A microwave component including a waveguide comprising at least one upper layer having at least one electrically conductive surface, a lower layer having at least one electrically conductive surface, and a central layer intermediate between the upper layer and the lower layer, said layers defining a zone of propagation for an electromagnetic wave, the propagation zone extending along a propagation axis (X-X), each of the upper layer, lower layer and central layer extending parallel to a plane, defined by the propagation axis (X-X) and by a transverse axis (Y-Y) orthogonal to the propagation axis (X-X), the propagation zone comprising a cavity, the cavity being bounded by the upper layer, the lower layer, and, laterally, by two opposite lateral edges of the central layer, the lateral edges of the central layer extending parallel to the propagation axis, the cavity being filled with a fluid having a dielectric constant, or defining a sealed closed volume and being empty of fluid. the waveguide comprising at least one dielectric strip placed in the propagation zone extending along a longitudinal direction parallel to the propagation axis (X-X), and wherein: * the dielectric strip is defined in one of the upper layer and the lower layer, or; * the dielectric strip is placed in the cavity away from the lateral edges of the cavity, the dielectric strip having a thickness smaller than the height of the cavity, the thickness of the dielectric strip and the height of the cavity being taken along a direction (Z-Z) orthogonal to the propagation axis (X-X) and the transverse axis (Y-Y). the propagation zone extending along a propagation axis (X-X), each of the upper layer, lower layer and central layer extending parallel to a plane, defined by the propagation axis (X-X) and by a transverse axis (Y-Y) orthogonal to the propagation axis (X-X), the propagation zone comprising a cavity, the cavity being bounded by the upper layer, the lower layer, and, laterally, by two opposite lateral edges of the central layer, the lateral edges of the central layer extending parallel to the propagation axis, the cavity being filled with a fluid having a dielectric constant, or defining a sealed closed volume and being empty of fluid. the waveguide comprising at least one dielectric strip placed in the propagation zone extending along a longitudinal direction parallel to the propagation axis (X-X), and wherein: * the dielectric strip is defined in one of the upper layer and the lower layer, or; * the dielectric strip is placed in the cavity away from the lateral edges of the cavity, the dielectric strip having a thickness smaller than the height of the cavity, the thickness of the dielectric strip and the height of the cavity being taken along a direction (Z-Z) orthogonal to the propagation axis (X-X) and the transverse axis (Y-Y). * the dielectric strip is defined in one of the upper layer and the lower layer, or; * the dielectric strip is placed in the cavity away from the lateral edges of the cavity, the dielectric strip having a thickness smaller than the height of the cavity, the thickness of the dielectric strip and the height of the cavity being taken along a direction (Z-Z) orthogonal to the propagation axis (X-X) and the transverse axis (Y-Y).