A multi-channel rotary joint, designed to couple a stationary and a rotary component of a radar system to each other, comprises a main channel centered on the axis of rotation and a plurality of axially spaced ancillary channels coaxially surrounding the main channel. Each ancillary channel is formed by two capacitively coupled coplanar rings respectively carried on a stationary and on a rotatable dielectric sleeve centered on the axis, each ring comprising two concentric annular conductor strips on the inner and the outer sleeve surface. The inner and outer conductor strips of each ring are interrupted by small equispaced gaps which are relatively offset to form overlapping segments of two concentric transmission lines which are electrically continuous except at one point at which the line is coupled to a respective balun also formed by arcuate conductor strips.