How does cable bending radius affect the electrical performance of a flexible coaxial assembly?
Bend Radius and Cable Performance
When a coaxial cable is bent, the outer wall stretches while the inner wall compresses. This deformation changes the cross-sectional geometry of the cable, affecting its electromagnetic properties. If the bend radius is too tight, the changes become permanent and the cable is damaged.
| Parameter | Semi-Rigid | Conformable | Flexible |
|---|---|---|---|
| Loss (dB/m at 10 GHz) | 0.8-2.5 | 1.0-3.0 | 1.5-5.0 |
| Phase Stability | Excellent | Good | Fair |
| Bend Radius | Fixed after forming | Hand-formable | Continuous flex OK |
| Shielding (dB) | >120 | >90 | >60-90 |
| Cost (relative) | 2-5x | 1.5-3x | 1x |
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
- Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture
Frequently Asked Questions
How does bending affect insertion loss?
A single gentle bend (at 5× diameter radius) adds approximately 0.01-0.05 dB loss at 10 GHz. A tight bend (at the minimum radius) can add 0.1-0.3 dB. Multiple tight bends in the same cable can accumulate significant loss. Keep bend radii as large as physically possible.
Does bending affect return loss?
Yes. The impedance change at the bend creates a reflection. For a gentle bend, the return loss impact is minimal (<0.1 dB). For a tight bend, the return loss can degrade by 5-10 dB, potentially causing system problems in impedance-sensitive applications.
Can bent semi-rigid cable be straightened?
No. Semi-rigid cable that has been bent cannot be straightened without risking damage to the inner conductor and dielectric. Once bent, it should remain in that shape. To change the routing, cut a new piece and re-form it. This is why semi-rigid cable assemblies are carefully planned before bending.