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Radio frequency (RF) is any of the electromagnetic wave frequencies that lie in the range extending from around to , which include those frequencies used for communications or radar signals.〔 〕 RF usually refers to electrical rather than mechanical oscillations. However, mechanical RF systems do exist (see mechanical filter and RF MEMS). Although radio ''frequency'' is a rate of oscillation, the term "radio frequency" or its abbreviation "RF" are used as a synonym for radio – i.e., to describe the use of wireless communication, as opposed to communication via electric wires. Examples include: * Radio-frequency identification * ISO/IEC 14443-2 ''Radio frequency power and signal interface'' == Special properties of RF current == Electric currents that oscillate at radio frequencies have special properties not shared by direct current or alternating current of lower frequencies. * The energy in an RF current can radiate off a conductor into space as electromagnetic waves (radio waves); this is the basis of radio technology. * RF current does not penetrate deeply into electrical conductors but tends to flow along their surfaces; this is known as the skin effect. For this reason, when the human body comes in contact with high power RF currents it can cause superficial but serious burns called ''RF burns (Radiation burns)''. * RF currents applied to the body often do not cause the painful sensation of electric shock as do lower frequency currents. This is because the current changes direction too quickly to trigger depolarization of nerve membranes. * RF current can easily ionize air, creating a conductive path through it. This property is exploited by "high frequency" units used in electric arc welding, which use currents at higher frequencies than power distribution uses. * Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric insulator of a capacitor. * When conducted by an ordinary electric cable, RF current has a tendency to reflect from discontinuities in the cable such as connectors and travel back down the cable toward the source, causing a condition called standing waves. Therefore, RF current must be carried by specialized types of cable called transmission line. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Radio frequency」の詳細全文を読む スポンサード リンク
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