Extremely high frequency
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| extremely high frequency (EHF) |
|---|
| Cycles per second: 30 GHz to 300 GHz Wavelength: 10 mm to 1 mm |
Extremely high frequency is the highest radio frequency band. EHF runs the range of frequencies from 30 to 300 gigahertz, above which electromagnetic radiation is considered to be low (or far) infrared light, also referred to as Terahertz radiation. This band has a wavelength of ten to one millimetre, giving it the name millimeter band or millimetre wave.
Radio signals in this band are extremely prone to atmospheric attenuation, making them of very little use over long distances. Even over relatively short distances, rain fade is a serious problem, caused when absorption by rain reduces signal strength.
Applications
This band is commonly used in radio astronomy.
In the United States, the band 38.6 - 40.0 GHz is used for licensed high-speed microwave data links, and the 60 GHz band can be used for unlicensed short range (1.7 km) data links with data throughputs up to 2.5 Gbit/s (gigabits per second). This is a Civil Air Patrol frequency, as well. It is used commonly in flat terrain.
The 71-76, 81-86 and 92-95 GHz bands are also used for point-to-point high-bandwidth communication links. These frequencies, as opposed to the 60 GHz frequency, require a transmitting license in the US from the FCC, though do not suffer from the effects of oxygen absorption as the 60 GHz does. There are plans for 10 GBit/s links using these frequencies as well. In the case of the 92-95 GHz band, a 100 MHz band has been reserved for space-borne radios, making this upper band limited to a transmission rate of only a few gigabits.
Applications include radar systems with high resolution. A recent development has been imagers for security applications as clothing and other organic materials are translucent in some mm-wave atmospheric windows.
See also
| Radio spectrum | ||||||||||
| ELF | SLF | ULF | VLF | LF | MF | HF | VHF | UHF | SHF | EHF |
| 3 Hz | 30 Hz | 300 Hz | 3 kHz | 30 kHz | 300 kHz | 3 MHz | 30 MHz | 300 MHz | 3 GHz | 30 GHz |
| 30 Hz | 300 Hz | 3 kHz | 30 kHz | 300 kHz | 3 MHz | 30 MHz | 300 MHz | 3 GHz | 30 GHz | 300 GHz |
| The Electromagnetic Spectrum (Sorted by wavelength, short to long) Gamma ray | X-ray | Ultraviolet | Visible spectrum | Infrared | Terahertz radiation | Microwave | Radio waves
Visible (optical) spectrum: Violet | Blue | Green | Yellow | Orange | Red
Microwave spectrum: W band | V band | K band: Ka band, Ku band | X band | C band | S band | L band
Radio spectrum: EHF | SHF | UHF | VHF | HF | MF | LF | VLF | ULF | SLF | ELF
Wavelength designations : Microwave | Shortwave | Mediumwave | Longwave
|
External links
Academic
- Tomislav Stimac, "[Definition of frequency bands (VLF, ELF... etc.)]". IK1QFK Home Page (vlf.it).
- [Millimetre-Wave Technology Group] at Rutherford-Appleton Laboratory
- [St. Andrews University mm-wave group]
- [A Survey of University Capabilities for a New Canadian Radio Telescope]
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