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 (XY), 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 (XY), 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). <EOS>