2026-09-24
The outer conductor of a coaxial cable has two basic functions: serving as the return conductor of the transmission loop, and shielding against external electromagnetic interference. To ensure uniform characteristic impedance and high return loss, the outer conductor dimensions must be strictly controlled, and the copper must be high quality, highly conductive, and impurity-free.
Three main structures are used in practice:
1. Braid plus laminated tape composite: evolved from the single-braid structure, offering good flexibility, light weight, and reliable connections. A well-designed composite structure significantly improves shielding performance and is the most widely used today.
2. Longitudinally overlapped aluminum-plastic tape: high shielding effectiveness and low manufacturing cost, but the longitudinal slit allows some leakage, narrowing its application range.
3. Metal tube: longitudinally welded copper or aluminum tape, or seamless drawn tube, offers the best shielding but lower flexibility, commonly used for trunk cables.
The number of braid strands and copper coverage determine the anti-interference capability: a loose braid blocks about 80% of interference signals, suitable for low-interference environments, while strong-interference environments require high-coverage braid or metal tube outer conductors.