This article is about the protective properties of RF shielding or RF protection. RF protection protects sensitive electronic equipment from radiofrequency (“RF”) electromagnetic radiation. The purpose behind much of this type of protection is to reduce radio-frequency interference with other equipment and with people nearby.
Radio frequency interference is a disturbance that occurs in electronic circuits and systems containing active electronic components, usually caused by an unwanted RF signal. Such interference may affect equipment performance, create undesired operations such as malfunction or sometimes cause damage to equipment.
A protective shield (shielding or screening) is a conductive enclosure for electromagnetic radiation and electric currents. An ideal protective shield would be free of holes, gaps, or seams through which electromagnetic fields could propagate. However, it may be physically impossible to eliminate all holes and gaps, and their presence is often unavoidable due to the nature of the manufacturing process.
Protective shields are commonly used in electrical engineering to prevent electromagnetic interference with other devices. The main use of a protective shield is usually that of preventing electromagnetic interference with other devices.
An ideal protective shield would be completely closed to electromagnetic fields. However, it may be physically impossible to eliminate all holes and gaps, and their presence is often unavoidable due to the nature of the manufacturing process.
A typical protective shield consists of several conductive plates arranged in a grid pattern or mesh designed to block radiation least efficiently (in other words, the radiation must pass through many paths before it can reach its target).
Shielded cables, sometimes called screened cables or balanced cables, are shielded with a shield of braided wire or foil to keep unwanted RF signals from entering or leaving an electronic device. There are two kinds of shielded cable: balanced and unbalanced. Shielding confers several benefits to the cable system it is used with, including reduced emissions and immunity from electromagnetic interference. In unbalanced cables such as coaxial cables, the shield acts as the ground conductor in the cable.
There are several types of shielding that have been used. The most common is the “Wien” effect. This magnetic field creates a self-shielding effect in which electric currents moving through a conductor create an electromagnetic field in the same conductor. Further development of this principle is the use of ferrite cores in shielded transformers.
Many electronic devices require the protection of shielding. The main uses are usually environmental control, cable television, and high-frequency circuit design. Shielded equipment is often used in conjunction with radiofrequency receivers and transmitters. Shielding is used to prevent unwanted radio signals from entering or leaving the equipment. In addition to prevention, it also reduces emissions into the environment by preventing leakage or radiation from occurring during the normal operation of the equipment.
Material used to shield electronic devices usually comes in the form of a foil used to create ground planes. In this form, it is called Electrostatic Dissipative Polyethylene. The foil material can be conductive or non-conductive, and the dielectric properties of ESD Shielding will depend on the thickness specified in mils (thousandths of an inch).
Electromagnetic interference is a common phenomenon in electronic circuits and systems. It can be reduced through proper shielding or a Faraday Cage in many cases. The purpose behind much of this kind of protection is to protect against radio-frequency interference with other equipment and with people nearby.