Phase-stable v Flexure
Coaxial RF Cable Assemblies

Phase-stability vs flexure is largely affected by changes in the outer conductor as a cable is flexed or even moved. Movement causes small changes in dimensions along the length of the cable resulting in multiple impedance discontinuities. These variations are additive and can significantly affect VSWR and phase distortion. In addition to small dimensional changes in the core (center conductor and dielectric), small gaps in the outer conductor during flexure create small areas of decreased shielding effectiveness. While the dimensional changes in the cylindrical core cannot, to a significant extent, be controlled; outer conductor constructions have been developed to significantly reduce discontinuities in the outer conductor. Some vendors utilized additional shielding layers and/or bonding layers to prevent movement of braids during flexure. Suppliers include Gore PhaseFlex® and Storm Products AccuTest®. Other vendors have improved the outer conductor with an interlocking coil that nearly eliminates the gaps in shielding effectiveness along the length of the cable and limits bending to a larger bend radius. This latter construction also improves durability as its construction resembles common spiral-wrapped RF cable armor. Suppliers include Flexco Microwave and MegaPhase GrooveTube®.
As Koaxis is primarily a supplier of small diameter cable assemblies, these solutions are more difficult to implement. At this time, Koaxis is NOT a supplier of RF cable assemblies with improved Phase-stability vs Flexure. There is good news for some applications, however.

A Low-tech Approach...
Armored Semi-rigid Cable Assemblies

We know it's blasphemy in a high-tech world. But, if you dare, ask yourself these questions,

- Is my test setup sensitive to phase changes?
- Is my test setup static or undisturbed once setup?
- Can I calibrate for differences in Phase-length between multiple test cables?
- Am I open to more cost-effective solutions for VNA and Test cables?

If you answered "yes" to these questions, then perhaps a set of semi-rigid RF cable assemblies is right for you. Not only does the phase remain unchanged when semi-rigid assemblies are set up, they can also be armored to allow for protection and bending by hand without fear of kinking or breaking the precious outer conductor beneath. It's what we use here at Koaxis, so we have found that others enjoy this unique approach to VNA and Test cables, too. All of this for a fraction of the price of the RF cable assemblies that you are using now. It's not for everyone, but, it is available now. We (will soon) have this solution available Ready 48™.