The primary function of the shield in coaxial cables is to act as a physical barrier that protects the inner conductor, which carries the signal, from external sources of electromagnetic interference. The shield is usually composed of highly conductive materials, such as copper, aluminum, or a combination of both, which have excellent electrical properties for blocking unwanted signals. By enveloping the inner core, the shield prevents external electromagnetic fields from penetrating the cable and interfering with the signal transmission. When external EMI impinges on the cable, the shield absorbs and redirects the interference, effectively preventing it from reaching the inner conductor. This is especially important in environments where high levels of electromagnetic noise are common, such as industrial settings or areas with dense electrical infrastructure. Without this protective layer, signals would be more susceptible to distortion and loss of quality due to the absorption of external interference.
Grounding is an essential feature of the shielding system in coaxial cables. In many applications, the shield is grounded at both ends of the cable, providing a direct pathway for unwanted interference to flow safely into the ground. This grounding mechanism ensures that any EMI that is absorbed by the shield does not remain trapped within the cable but is instead diverted away from the signal transmission path. By providing a low-resistance path to the earth, the grounding process not only prevents EMI from interfering with the signal but also helps to minimize the risk of electrical shock or equipment damage. This is particularly important in environments where the cable is exposed to fluctuating electrical currents, such as in industrial machinery or medical equipment. Grounding is also highly effective in eliminating low-frequency interference, such as power line hum or electrical noise generated by nearby devices.
The shield in coaxial cables serves a dual role: reflecting and absorbing electromagnetic interference. When EMI encounters the shield, part of the electromagnetic energy is reflected back toward the source, preventing it from entering the cable and affecting the signal. The remaining energy is absorbed by the conductive material in the shield, where it is dissipated as heat, further reducing the chances of interference. The efficiency of this reflection and absorption process depends on the material properties of the shield and its design. Copper, for instance, is a highly effective conductor and reflects a significant portion of external EMI. Aluminum, though less conductive than copper, is still effective at both reflecting and absorbing electromagnetic energy. Coaxial cable manufacturers select materials for shielding that offer the best balance of performance, durability, and cost-effectiveness for the intended application. In higher-interference environments, such as industrial plants or military operations, the shielding is often designed with thicker or more advanced materials that enhance the reflection and absorption capabilities, ensuring that more EMI is neutralized before it reaches the inner conductor.
