ROTARY SWAGING TECHNOLOGY

The patented rotary swaging (RS) technology addresses the common trade-off between flexibility and low attenuation. The inner conductor possesses the surface of a solid wire and the core of a stranded wire, providing flexibility and phase stability without compromising on attenuation or return loss.

Trade-off

Existing coaxial cables on the market today consist of either a solid or stranded inner conductor. Thus, the current cable selection is always a trade-off, with users having to choose between lower loss (solid wire) or more flexibility (stranded wire).

The stranded wire causes a higher attenuation compared to the solid wire. The signal only flows in the outermost few micrometers of the inner conductor and so the signal path in the strand is longer than in the solid wire. This behaviour is more pronounced with microwave signals than with low frequency signals and it is called the ‘skin effect’. In addition, there are the contact resistances between the individual stranded wires, which also contribute to higher damping.

On the contrary, microwave cables with solid wires have greater phase deflection through bending than cables with stranded wires. This is especially true for cable types with a dielectric diameter greater than 2 mm. Here, the cable length is slightly reduced by bending movements, which results in a deformation of the inner conductor. This leads to the phase shift. The effect is caused by interaction with the various construction elements of the cable. To plastically deform the individual wires of the strand, a stronger bending movement is required. This leads to smaller length changes in the overall construct of a microwave cable and to a more stable phase versus bending behaviour.
 

Rotary swaging technology

To resolve the trade-off issue facing the coaxial cable market, our supplier HUBER+SUHNER combined the advantages of the solid and the stranded wire into one product: a low loss, phase stable and flexible inner conductor cable with a long lifetime. To achieve this, HUBER+SUHNER has launched a two-in-one solution, enabled by its patented rotary swaging technology.

Rotary swaging is a process of mechanical deformation and is achieved by generating repeated blows to a conventional strand. Using hammers, the surface of the stranded wire is smoothened. A nearly perfect round and smooth surface is guaranteed.

This smooth surface prevents the occurrence of possible discontinuities in the microwave cable, which reduces regular return loss peaks. The conventional stranded wire has a regular structure and is thus more susceptible to return loss peaks caused by changes in diameter and hence impedance. As a result of the changes, part of the microwave signal is reflected. If several discontinuities occur at regular intervals, this results in a strongly reflected signal at a certain frequency – called return loss peak. The rotary swaged stranded wire eliminates this risk by mimicking the signal path of the solid wire and through that improving the return loss level as well. Additionally, the contact resistance is reduced when compared with a conventional, true concentric stranded wire leading to a lower insertion loss.