# Super high frequency

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Range 3-30 GHz of the electromagnetic spectrum

Super high frequency Frequency range 3 to 30 GHz Wavelength range 10 to 1 cm Related bands F G H I J K (NATO) S C X Ku K Ka (IEEE)

Radio bands ITU 1 (ELF) 2 (SLF) 3 (ULF) 4 (VLF) 5 (LF) 6 (MF) 7 (HF) 8 (VHF) 9 (UHF) 10 (SHF) 11 (EHF) 12 (THF) EU / NATO / US ECM A B C D E F G H I J K L M N IEEE HF VHF UHF L S C X Ku K Ka V W mm Other TV and radio I II III IV V VI v t e

**Super high frequency** (**SHF**) is the [ITU](/source/International_Telecommunication_Union) designation[1][2] for [radio frequencies](/source/Radio_frequency) (RF) in the range between 3 and 30 [gigahertz](/source/Gigahertz) (GHz). This band of frequencies is also known as the **centimetre band** or **centimetre wave** as the [wavelengths](/source/Wavelength) range from one to ten centimetres. These frequencies fall within the [microwave](/source/Microwave) band, so radio waves with these frequencies are called microwaves. The small wavelength of microwaves allows them to be directed in narrow beams by [aperture antennas](/source/Antenna_aperture) such as [parabolic dishes](/source/Parabolic_antenna) and [horn antennas](/source/Horn_antenna), so they are used for [point-to-point](/source/Point-to-point_(telecommunications)) communication and data links[3] and for [radar](/source/Radar). This frequency range is used for most [radar](/source/Radar) transmitters, [wireless LANs](/source/Wireless_LAN), [satellite communication](/source/Satellite_communication), [microwave radio relay](/source/Microwave_radio_relay) links, [satellite phones](/source/Satellite_phone) ([S band](/source/S_band)), and numerous short range terrestrial data links. They are also used for heating in industrial [microwave heating](/source/Microwave_heating), medical [diathermy](/source/Diathermy), [microwave hyperthermy](/source/Hyperthermy) to treat cancer, and to cook food in [microwave ovens](/source/Microwave_oven).

Frequencies in the SHF range are often referred to by their [IEEE radar band](/source/Radio_band#IEEE) designations: [S](/source/S_band), [C](/source/C_band_(IEEE)), [X](/source/X_band), [Ku](/source/Ku_band), [K](/source/K_band_(IEEE)), or [Ka band](/source/Ka_band), or by similar [NATO](/source/NATO_bands) or EU designations.

## Propagation

A variety of [parabolic antennas](/source/Parabolic_antenna) on a [communications tower](/source/Radio_masts_and_towers) in [Australia](/source/Australia) for [point-to-point](/source/Point-to-point_(telecommunications)) [microwave communication](/source/Microwave_transmission) links.  Some have white plastic [radomes](/source/Radome) over their apertures to protect against [rain](/source/Rain).

[X-band](/source/X-band) (8 - 12 GHz) [marine radar](/source/Marine_radar) antenna on a [ship](/source/Ship). The rotating bar sweeps a vertical fan-shaped beam of microwaves around the water surface to the horizon, detecting nearby ships and other obstructions

[Microwaves](/source/Microwave) propagate solely by [line of sight](/source/Line-of-sight_propagation); because of the small [refraction](/source/Refraction) due to their short wavelength, the [groundwave](/source/Groundwave) and ionospheric reflection ([skywave](/source/Skywave) or "skip" propagation) seen with lower frequency radio waves do not occur.[4] Although in some cases they can penetrate building walls enough for useful reception, unobstructed rights of way cleared to the first [Fresnel zone](/source/Fresnel_zone) are usually required. Wavelengths are small enough at microwave frequencies that the antenna can be much larger than a wavelength, allowing highly [directional](/source/Directional_antenna) (high [gain](/source/Antenna_gain)) [antennas](/source/Antenna_(radio)) to be built which can produce narrow beams. Therefore, they are used in [point-to-point](/source/Point-to-point_(telecommunications)) terrestrial communications links, limited by the visual horizon to 30–40 miles (48–64 km). Such [high gain antennas](/source/High_gain_antenna) allow [frequency reuse](/source/Frequency_reuse) by nearby transmitters. They are also used for communication with [spacecraft](/source/Spacecraft) since the waves are not [refracted](/source/Refraction) (bent) when passing through the [ionosphere](/source/Ionosphere) like lower frequencies.

The [wavelength](/source/Wavelength) of SHF waves creates strong reflections from metal objects the size of automobiles, aircraft, and ships, and other vehicles. This and the narrow [beamwidths](/source/Beamwidth) possible with high gain antennas and the low atmospheric attenuation as compared with higher frequencies make SHF the main frequencies used in [radar](/source/Radar). Attenuation and scattering by moisture in the atmosphere increase with frequency, limiting the use of high SHF frequencies for long range applications.

Small amounts of microwave energy are randomly scattered by water vapor molecules in the [troposphere](/source/Troposphere). This is used in [troposcatter](/source/Troposcatter) communications systems, operating at a few GHz, to communicate beyond the horizon. A powerful microwave beam is aimed just above the horizon; as it passes through the [tropopause](/source/Tropopause) some of the microwaves are scattered back to Earth to a receiver beyond the horizon. Distances of 300 km can be achieved. These are mainly used for military communication.

## Antennas

Microwaves are often carried by [waveguide](/source/Waveguide), such as this example from an [air traffic control](/source/Air_traffic_control) [radar](/source/Radar), since other types of cable have large power losses at SHF frequencies.

The [wavelength](/source/Wavelength) of SHF waves is short enough that efficient transmitting antennas are small enough to be conveniently mounted on handheld devices, so these frequencies are widely used for wireless applications. For example a [quarter wave whip](/source/Whip_antenna) antenna for the SHF band is between 2.5 and 0.25 centimeters long. [Omnidirectional antennas](/source/Omnidirectional_antenna) have been developed for applications like wireless devices and [cellphones](/source/Cellphone) that are small enough to be enclosed inside the device's case. The main antenna used for these devices is the printed [inverted F antenna](/source/Inverted_F_antenna) (PIFA) consisting of a [monopole antenna](/source/Monopole_antenna) bent in an L shape, fabricated of copper foil on the [printed circuit board](/source/Printed_circuit_board) inside the device. Small [sleeve dipoles](/source/Dipole_antenna) or [quarter-wave monopoles](/source/Monopole_antenna) are also used. The [patch antenna](/source/Patch_antenna) is another common type, often integrated into the skin of aircraft.

The wavelengths are also small enough that SHF waves can be focused into narrow beams by [high gain](/source/High_gain_antenna) [directional antennas](/source/Directional_antenna) from a half meter to five meters in diameter. Directive antennas at SHF frequencies are mostly [aperture antennas](/source/Aperture_(antenna)), such as [parabolic antennas](/source/Parabolic_antenna) (the most common type), [lens](/source/Lens_antenna), [slot](/source/Slot_antenna) and [horn antennas](/source/Horn_antenna). Large parabolic antennas can produce very narrow beams of a few degrees or less, and often must be aimed with the aid of a [boresight](/source/Antenna_boresight). Another type of antenna practical at microwave frequencies is the [phased array](/source/Phased_array), consisting of many dipoles or [patch antennas](/source/Patch_antenna) on a flat surface, each fed through a [phase shifter](/source/Phase_shifter), which allows the array's beam to be steered electronically. The short wavelength requires great mechanical rigidity in large antennas, to ensure that the radio waves arrive at the feed point in phase.

### Waveguide

At microwave frequencies, the types of cable ([transmission line](/source/Transmission_line)) used to conduct lower frequency radio waves, such as [coaxial cable](/source/Coaxial_cable), have high power losses. Therefore, to transport microwaves between the transmitter or receiver and the antenna with low losses, a special type of metal pipe called [waveguide](/source/Waveguide_(electromagnetism)) must be used. Because of the high cost and maintenance requirements of long waveguide runs, in many microwave antennas the output stage of the transmitter or the [RF front end](/source/RF_front_end) of the receiver is located at the antenna.

## Advantages

SHF frequencies occupy a "sweet spot" in the [radio spectrum](/source/Radio_spectrum) which is currently being exploited by many new radio services.[5] They are the lowest frequency band where radio waves can be directed in narrow beams by conveniently sized antennas so they do not interfere with nearby transmitters on the same frequency, allowing frequency reuse. On the other hand, they are the highest frequencies which can be used for long distance terrestrial communication; higher frequencies in the [EHF](/source/Extremely_high_frequency) (millimeter wave) band are highly absorbed by the atmosphere, limiting practical propagation distances to one kilometer or less. The high frequency gives microwave communication links a very large information-carrying capacity ([bandwidth](/source/Bandwidth_(signal_processing))). In recent decades many new solid state sources of microwave energy have been developed, and microwave [integrated circuits](/source/Integrated_circuit) for the first time allow significant [signal processing](/source/Signal_processing) to be done at these frequencies. Sources of EHF energy are much more limited and in an earlier state of development.

## See also

- [Knife-edge effect](/source/Knife-edge_effect)

- [Microwave burn](/source/Microwave_burn)

## References

1. **[^](#cite_ref-1037B_1-0)** [*US Federal Standard 1037B: Telecommunications, Glossary of Telecommunications Terms*](https://books.google.com/books?id=zYLXU4fkD34C&pg=RA15-PA18). Office of Technology Standards, General Services Administration. 3 June 1991. pp. S-18.

1. **[^](#cite_ref-itu-2015-acts_2-0)** [*Final Acts WRC-15*](https://www.itu.int/dms_pub/itu-r/opb/act/R-ACT-WRC.12-2015-PDF-E.pdf) (PDF). World Radiocommunication Conference. Geneva, Switzerland: International Telecommunications Union. 2015. p. 4. Retrieved 2025-01-12.

1. **[^](#cite_ref-Freedman_3-0)** Freedman, S. (September 1946). ["Two-way radio for everyone"](https://www.worldradiohistory.com/Archive-Radio-News/40s/Radio-News-1946-09.pdf) (PDF). *Radio News*. **36** (3). New York: Ziff-Davis Publications: 25–27. Retrieved March 24, 2014. This article from the beginning of the microwave era predicted the future value of microwaves for point-to-point communication.

1. **[^](#cite_ref-Seybold_4-0)** Seybold, John S. (2005). [*Introduction to RF Propagation*](https://books.google.com/books?id=4LtmjGNwOPIC&dq=cross+polarization+discrimination&pg=PA57). John Wiley and Sons. pp. 55–58. [ISBN](/source/ISBN_(identifier)) [0471743682](https://en.wikipedia.org/wiki/Special:BookSources/0471743682).

1. **[^](#cite_ref-Lee_5-0)** Lee, Thomas H. (2004). [*Planar Microwave Engineering: A Practical Guide to Theory, Measurement, and Circuits*](https://books.google.com/books?id=cnhhBAAAQBAJ&pg=PA27). Cambridge University Press. p. 27. [ISBN](/source/ISBN_(identifier)) [1316175774](https://en.wikipedia.org/wiki/Special:BookSources/1316175774).

## External links

- Tomislav Stimac, "*[Definition of frequency bands (VLF, ELF... etc.)](http://www.vlf.it/frequency/bands.html)*". IK1QFK Home Page (vlf.it).

- Inés Vidal Castiñeira, "*[Celeria: Wireless Access To Cable Networks](http://www.broadbandhomecentral.com/report/backissues/Report0308_3.html)*"

v t e Radio spectrum (ITU) ELF 3 Hz/100 Mm 30 Hz/10 Mm SLF 30 Hz/10 Mm 300 Hz/1 Mm ULF 300 Hz/1 Mm 3 kHz/100 km VLF 3 kHz/100 km 30 kHz/10 km LF 30 kHz/10 km 300 kHz/1 km MF 300 kHz/1 km 3 MHz/100 m HF 3 MHz/100 m 30 MHz/10 m VHF 30 MHz/10 m 300 MHz/1 m UHF 300 MHz/1 m 3 GHz/100 mm SHF 3 GHz/100 mm 30 GHz/10 mm EHF 30 GHz/10 mm 300 GHz/1 mm THF 300 GHz/1 mm 3 THz/0.1 mm Radio portal

v t e Electromagnetic spectrum Gamma rays X-rays Ultraviolet Visible Infrared Microwave Radio ← higher frequencies, higher energy, shorter wavelengths longer wavelengths, lower frequencies, lower energy → Gamma rays Very-high-energy Ultra-high-energy X-rays Soft X-ray Hard X-ray High-energy X-rays Ultraviolet Extreme ultraviolet Vacuum ultraviolet Lyman-alpha FUV MUV NUV UVC UVB UVA Visible (optical) Violet Blue Cyan Green Yellow Orange Red Infrared NIR (Bands: J, K, H) SWIR MWIR (Bands: L, M, N) LWIR FIR Microwaves W band V band Q band Ka band K band Ku band X band C band S band L band Radio THF EHF SHF UHF VHF HF MF LF VLF ULF SLF ELF Wavelength types Microwave Shortwave Medium wave Longwave

Authority control databases International GND Other Yale LUX

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Adapted from the Wikipedia article [Super high frequency](https://en.wikipedia.org/wiki/Super_high_frequency) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Super_high_frequency?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.