Rotating electrical joints with continuous metallic connections

The need for very low noise, low RF loss dynamic rotating electrical connections exist, in particular for pointing mechanisms requiring very high stability. Four basic designs are presented: • the cable-wrap (clock-spring shaped flat cable) • the vertical goose-neck (flat cable squeezed between two rotating cylinders) • the horizontal goose-neck (flat cable squeezed between two parallel disks) • the twist cable (twisted cable bundle in a cylindrical housing). The choice of the appropriate design is highly dependent on the following parameters: available space and shape, torque, angular range, current, signal type to be transferred. A discussion of the design selection parameters, and typical achievable performances will be presented. The cable wrap design is favourable when the Housing diameter (outer diameter O.D.) to Drum diameter (inner diameter I.D.) ratio is large. When this ratio tends to unity, the gooseneck design is preferable and is essentially limited by the bending radius of the cable sheet that is directly related to the life of the mechanism.