Coaxial electric wire are used for the transmission of Radio Frequency energy.Coaxial wire is a two conductor electrical wire on alternating positions. A coaxial cable consists of an inner conductor, surrounded by an insulating layer which is then surrounded by another conductive layer, typically a fine woven braid or a thin metallic foil, and eventually outer covering of insulation. The center conductor and the outer conductor, or shield, are configured in such a way that they form concentric cylinders with a common axis that’s why are termed and name co-axial.
The shield serves four basic factors. First is to keep the desired electrical currents inside, and the second is to keep the undesired currents outside. High-quality cables use double-shield construction in which first shield is a braid and the other is a thin, coated aluminum foil underneath the braid. The foil screen reduces the transfer impedance at higher frequencies. As the frequency increases, the inside current is brought to the outside surface by the braid weave.
Coaxial cable functions as an electromagnetic energy interceptor. It prevents electrical interference from traveling to the cable’s center conductor and muck-up the data signal. In addition to blocking renegade electrical waves, shielding also ensures any potentially disruptive energy is disposed through efficient and proper grounding. In order for shielding to adequately perform its duties, it needs to be highly conductive, and typically comes in two forms: wire braid and foil.
Braid Shield: A braid is a woven mesh of bare or tinned copper wires. The braid provides a low-resistance path to ground and is much easier to termination by crimping or soldering when attaching a connector. But braided shields do not provide 100% coverage. They allow small gaps in coverage. Depending on the tightness of the weave, braids typically provide between 75% and 90% coverage with 70% most sufficient.
Braid/Foil Shielding: A type of cable electric wire shield composed of a thin layer of mylar-backed aluminum foil in contact with a copper drain wire used to terminate it. The foil shield wire combination is low-cost, but it severely limits flexibility and thus breaks down under repeated flexing. It’s the only commonly available shield type that offers true 100% coverage.
Quad Shield: Quad-Shield based on a foil-braid-foil-braid shield. It has very popular for community antenna television (EMI) and applications in high electromagnetic/radio frequency interference locations such as urban areas.
Coaxial electric wire are perhaps the most common, basic, and easy to understand cables of common transmission line designs In coaxial electrical wires, shielding is an important part of the overall composition of the wire. Shielding not only protects the loss of signal in high frequency application, but also helps to prevent EMI and RFI in the circuit.