Abstract: A power dual-band rotary joint simultaneously operating on two frequency bands. A and is made up of a couple of transducers, each between two rectangular waveguides, respectively operating, on bands A and B, and a nested coaxial waveguide. The nested coaxial waveguide is made up of two concentric cylindric waveguides. The transducers are conceived in such a way that only modes with azimuthal symmetry are excited. The nested coaxial waveguide dimensions are chosen so that, on band B, the TM01 mode can propagate in the circular waveguide delimited by the internal surface of the smaller cylinder. The external surface of the smaller cylinder is the internal conductor of the coaxial working on band A, while the internal surface of the bigger cylinder is the external conductor of the same coaxial. The two transducers are connected through the nested waveguide.