A radiofrequency rotary joint for radio-electrically connecting together first and second parts of a rotary device for guiding RF waves and for transmitting RF electromagnetic signals between said first and second parts (6, 8) of said rotary device for guiding RF waves, the RF rotary joint comprising: - a first outer part (12; 212; 312; 422; 512), of generally annular shape, having a first internal electrically conductive surface (22; 222; 322; 522) for transmitting electromagnetic signals, which surface has rotational symmetry over an angular extension range of non-zero length and that is less than or equal to 360 degrees about a longitudinal axis of rotation (16; 216; 316; 516); and - a second part (18; 218; 318; 432; 518), inside the first part, having a second external electrically conductive surface (28; 228; 328; 528) for transmitting electromagnetic signals, which surface has rotational symmetry over the angular extension range about the longitudinal axis (16; 216; 316; 516) and is disposed without mechanical contact relative to the first internal surface and is free to rotate about the longitudinal axis (16; 216; 316; 516) over a predetermined angular rotation range; and - a whole number N, greater than or equal to 1, of separate RF transmission channel(s) Vi (4; 204, 206; 304, 306; 404, 406, 408, 410; 504), with i varying from 1 to N, between the first part and the second part of the rotary device for guiding RF waves; the first internal surface (22; 222; 322; 522) for transmitting electromagnetic signals comprising a series of a predetermined number NC, greater than or equal to 1 and less than or equal to N, of first sections of surfaces of revolution about the axis, located at different first levels L1(k), with k varying from 1 to NC, along the longitudinal axis of symmetry about first associated internal average radius(es) r1(k), with k varying from 1 to NC, and comprising N first RF access ports (32; 232, 233; 332, 333; 542) and first meta-material-based means (34; 234; 334; 544) for containing and guiding RF electromagnetic signals; and the second external surface (28; 228; 328; 528) for transmitting RF electromagnetic signals comprising a series of NC second sections of surfaces of revolution about the axis, respectively located at the different first levels L1(k), with k varying from 1 to NC, along the longitudinal axis of symmetry about second associated external average radius(es) r2(k), with k varying from 1 to NC, strictly less than the corresponding first internal average radius(es) r1(k), and comprising N second RF access ports (38; 238, 239; 338, 339; 546) and second meta-material-based means (40; 240; 340; 548) for containing and guiding RF electromagnetic signals; and the first and second RF transmission surfaces (22, 28; 222, 228; 322, 328; 522, 528) being configured by the first and second average radiuses r1(k), r2(k), the first longitudinal levels L1(k), with k varying from 1 to NC, the geometry of the first and second RF access ports, and the geometry of the first and second means (34, 40; 234, 240; 334, 340; 544, 548) for RF containment and guidance, such that: - each RF transmission channel Vi (4; 204, 206; 304, 306; 404, 406, 408, 410; 504), with i varying from 1 to N, comprises a first different curved sliding RF waveguide (42; 242, 243; 342, 343); and - the N first curved sliding RF waveguides (42; 242, 243; 342, 343) are angularly distributed over the NC first sections of surfaces of revolution about the axis, with each of the NC sections of surfaces of revolution about the axis being located along the longitudinal axis of symmetry at its first associated level L1(k), with k varying from 1 to NC. - a first outer part (12; 212; 312; 422; 512), of generally annular shape, having a first internal electrically conductive surface (22; 222; 322; 522) for transmitting electromagnetic signals, which surface has rotational symmetry over an angular extension range of non-zero length and that is less than or equal to 360 degrees about a longitudinal axis of rotation (16; 216; 316; 516); and - a second part (18; 218; 318; 432; 518), inside the first part, having a second external electrically conductive surface (28; 228; 328; 528) for transmitting electromagnetic signals, which surface has rotational symmetry over the angular extension range about the longitudinal axis (16; 216; 316; 516) and is disposed without mechanical contact relative to the first internal surface and is free to rotate about the longitudinal axis (16; 216; 316; 516) over a predetermined angular rotation range; and - a whole number N, greater than or equal to 1, of separate RF transmission channel(s) Vi (4; 204, 206; 304, 306; 404, 406, 408, 410; 504), with i varying from 1 to N, between the first part and the second part of the rotary device for guiding RF waves; - each RF transmission channel Vi (4; 204, 206; 304, 306; 404, 406, 408, 410; 504), with i varying from 1 to N, comprises a first different curved sliding RF waveguide (42; 242, 243; 342, 343); and - the N first curved sliding RF waveguides (42; 242, 243; 342, 343) are angularly distributed over the NC first sections of surfaces of revolution about the axis, with each of the NC sections of surfaces of revolution about the axis being located along the longitudinal axis of symmetry at its first associated level L1(k), with k varying from 1 to NC.