Radio frequency ( RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around 20 kHz . This is roughly between the upper limit of 300 GHz audio frequencies and the lower limit of infrared frequencies;  these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as  radio waves. Different sources specify different upper and lower bounds for the frequency range.
Electric currents that oscillate at radio frequencies ( RF currents) have special properties not shared by direct current or alternating current of lower frequencies.
Energy from RF currents in conductors can radiate 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. RF currents applied to the body often do not cause the painful sensation and muscular contraction of
electric shock that lower frequency currents produce.  This is because the current changes direction too quickly to trigger  depolarization of nerve membranes. However this does not mean RF currents are harmless; they can cause internal injury as well as serious superficial burns called . RF burns 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. This is because capacitive reactance in a circuit decreases with frequency. In contrast, RF current can be blocked by a coil of wire, or even a single turn or bend in a wire. This is because the
inductive reactance of a circuit increases with frequency. 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, such as coaxial cables.
radio spectrum of frequencies is divided into bands with conventional names designated by the International Telecommunications Union (ITU):
ITU designation IEEE bands
5–10 4 km
Extremely low frequency
4–10 3 km
Super low frequency
Ultra low frequency
Very low frequency
300 kHz – 3 MHz
1 km – 100 m
Very high frequency
300 MHz – 3 GHz
1 m – 10 cm
Ultra high frequency
UHF UHF, L, S
Super high frequency
SHF S, C, X, Ku, K, Ka
1 cm – 1 mm
Extremely high frequency
EHF Ka, V, W, mm
300 GHz – 3 THz
1 mm – 0.1 mm
Tremendously high frequency
Frequencies of 1 GHz and above are conventionally called
microwave, while frequencies of 30 GHz and above are designated  millimeter wave.
More detailed band designations are given by the standard IEEE letter- band frequency designations and the EU/NATO frequency designations. 
Radio frequencies are generated and processed within very many functional units such as
transmitters, receivers, computers, televisions, and mobile phones, to name a few. Radio frequencies are also applied in carrier current systems including telephony and control circuits.
RF circuit technology is widely used in wireless telecommunications, such as mobile communication. A typical smartphone contains a number of metal–oxide–semiconductor (MOS) integrated circuit (IC) RF chips, including RF CMOS chips such as a baseband cellular modem, RF transceiver, and wireless communication chips ( Wi-Fi, Bluetooth, and GPS receiver), as well as  LDMOS (lateral diffused MOS) RF power amplifiers.  
Radio frequency (RF) energy, in the form of radiating waves or electrical currents, has been used in medical treatments for over 75 years,
generally for minimally invasive surgeries using  radiofrequency ablation including the treatment of sleep apnea.
RF energy RF energy, also known as solid-state RF energy, is an electronic technology that uses solid-state electronics to provide RF electromagnetic radiation in a controlled manner for a wide range of applications, such as heating and home appliances. RF energy was introduced in the 2010s, as a replacement of traditional cavity magnetron tubes previously used for appliances such as microwave ovens. 
The basis for RF energy technology is the
LDMOS (laterally-diffused metal–oxide–semiconductor) transistor.   Common applications of LDMOS-based RF energy technology include the following.
Test apparatus for radio frequencies can include standard instruments at the lower end of the range, but at higher frequencies, the test equipment becomes more specialized.
While RF usually refers to electrical oscillations, mechanical RF systems are not uncommon: see
mechanical filter and RF MEMS.
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