Radio frequencies refer to the rate of oscillation of electromagnetic radio waves in the range of 3 kHz to 300 GHz. This band is used for communications transmission and broadcasting. Different radio frequencies are useful for different wireless technologies. For example, some frequencies are used to fore radio broadcasting; some frequencies are used for television broadcasting.
The use of radio waves is in many different types of communication which are defined in the electromagnetic spectrum. The electromagnetic spectrum contains all the frequencies of electromagnetic waves including visible light waves, microwaves, and radio waves. The radio wave spectrum is included in the electromagnetic waves spectrum having the frequency range between 3 kHz and 300 GHz.
The radio frequency spectrum is divided into different ranges called radio frequency bands for a huge number of applications including AM Radio, FM radio, television, cellular networks, Bluetooth, walkie-talkies, satellite communications, military applications, and much more. All wireless devices operate in the radio frequencies range of the electromagnetic spectrum.
The radiofrequency allocation from the spectrum is the responsibility of the International Telecommunication Union – Radiocommunication Sector (ITU-R). The radio frequency bands are allocated for different purposes. Some bands in the electromagnetic spectrum are used for applications, such as air traffic control and emergency responder communications networks. Some bands are free of license, for example, the Industrial, Scientific, and Medical band (ISM) and the unlicensed national information infrastructure (UNII) band.
The frequency range for wireless communication is 3 Hz to 300 GHz. The WLANs, Bluetooth, cellular, and satellite communication all operate in the microwave UHF, SHF, and EHF ranges. The WLAN frequency is 2.4GHz ISM bands and 5 GHz UNII bands. Specifically, the following frequency bands are allocated to 802.11 wireless LANs:
- 4 GHz (UHF)- 802.11b/g/n/ad
- 5 GHz (SHF)- 802.11a/n/ac/ad
- 60 GHz(EHF) – 802.11ad
The components of the electromagnetic spectrum are gamma-rays, x-rays, ultra-violet, visible light, infra-red, microwaves and radio-waves. We will discuss the radio-waves in detail. Radio wave has the longest wavelengths, from a few centimetres to thousands of meters. The figure below illustrates the radio frequency band.