Extremely high frequency

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Millimetre wave
)
Extremely high frequency
Extremely high frequency
Frequency range
30 to 300
mm
Related bands
  • K / L / M (NATO)
  • Ka / V / W / mm (IEEE)
Millimetre band (IEEE)
Frequency range
110 to 300 GHz
Wavelength range
2.73 to 1 mm
Related bands
EHF (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
IEEE
Other TV and radio

Extremely high frequency is the

terahertz band. Radio waves in this band have wavelengths from ten to one millimeter, so it is also called the millimeter band and radiation in this band is called millimeter waves, sometimes abbreviated MMW or mmWave. Millimeter-length electromagnetic waves were first investigated by Jagadish Chandra Bose, who generated waves of frequency up to 60 GHz during experiments in 1894–1896.[1]

Compared to lower bands, radio waves in this band have high

beam width, further increasing frequency reuse potential. Millimeter waves are used for military fire-control radar, airport security scanners, short range wireless networks
, and scientific research.

In a major new application of millimeter waves, certain

cell phone networks, 5G networks.[2] The design of millimeter-wave circuit and subsystems (such as antennas, power amplifiers, mixers and oscillators) also presents severe challenges to engineers due to semiconductor and process limitations, model limitations and poor Q factors of passive devices.[3]

Propagation

Atmospheric attenuation in dB/km as a function of frequency over the extremely high frequency band. Peaks in absorption at specific frequencies are a problem, due to atmosphere constituents such as water vapour (H2O) and molecular oxygen (O2). The vertical scale is logarithmic.

Millimeter waves propagate solely by

frequency reuse.[4]

Millimeter waves show "optical" propagation characteristics and can be reflected and focused by small metal surfaces and

Doppler shift of frequency can be significant even at pedestrian speeds.[4] In portable devices, shadowing due to the human body is a problem. Since the waves penetrate clothing and their small wavelength allows them to reflect from small metal objects they are used in millimeter wave scanners
for airport security scanning.

Applications

Scientific research

America, a millimeter wave radio telescope

This

band is commonly used in radio astronomy and remote sensing. Ground-based radio astronomy is limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter Array (ALMA
) due to atmospheric absorption issues.

Satellite-based

Advanced Microwave Sounding Unit (AMSU) on one NASA satellite (Aqua) and four NOAA (15–18) satellites and the special sensor microwave/imager (SSMI/S) on Department of Defense satellite F-16 make use of this frequency range.[8]

Telecommunications

In the United States, the band 36.0–40.0 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. 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 higher frequencies do not suffer from oxygen absorption, but require a transmitting license in the US from the Federal Communications Commission (FCC). There are plans for 10 Gbit/s links using these frequencies as well. In the case of the 92–95 GHz band, a small 100 MHz range has been reserved for space-borne radios, limiting this reserved range to a transmission rate of under a few gigabits per second.[9]

A CableFree MMW link installed in the UAE installed for Safe City applications, providing 1 Gbit/s capacity between sites. The links are fast to deploy and have a lower cost than fibre optics.

The band is essentially undeveloped and available for use in a broad range of new products and services, including high-speed, point-to-point wireless local area networks and broadband Internet access. WirelessHD is another recent technology that operates near the 60 GHz range. Highly directional, "pencil-beam" signal characteristics permit different systems to operate close to one another without causing interference. Potential applications include radar systems with very high resolution.

The

Gbit/s
, respectively.

Uses of the millimeter wave bands include point-to-point communications, intersatellite links, and point-to-multipoint communications. In 2013 it was speculated that there were plans to use millimeter waves in future 5G mobile phones.[10] In addition, use of millimeter wave bands for vehicular communication is also emerging as an attractive solution to support (semi-)autonomous vehicular communications.[11]

Shorter wavelengths in this band permit the use of smaller antennas to achieve the same high directivity and high gain as larger ones in lower bands. The immediate consequence of this high directivity, coupled with the high free space loss at these frequencies, is the possibility of a more efficient use of frequencies for point-to-multipoint applications. Since a greater number of highly directive antennas can be placed in a given area, the net result is greater

frequency reuse, and higher density of users. The high usable channel capacity in this band might allow it to serve some applications that would otherwise use fiber-optic communication or very short links such as for the interconnect of circuit boards.[12]

Weapons systems

Millimeter wave fire control radar for CIWS gun on Soviet aircraft carrier Minsk, Russia

Millimeter wave radar is used in short-range fire-control radar in tanks and aircraft, and automated guns (CIWS) on naval ships to shoot down incoming missiles. The small wavelength of millimeter waves allows them to track the stream of outgoing bullets as well as the target, allowing the computer fire control system to change the aim to bring them together. [citation needed]

With

U.S. Air Force has developed a nonlethal antipersonnel weapon system called Active Denial System (ADS) which emits a beam of millimeter radio waves with a wavelength of 3 mm (frequency of 95 GHz).[13] The weapon causes a person in the beam to feel an intense burning pain, as if their skin is going to catch fire. The military version had an output power of 100 kilowatts (kW),[14] and a smaller law enforcement version, called Silent Guardian that was developed by Raytheon later, had an output power of 30 kW.[15]

Security screening

Main article: Millimeter wave scanner

Clothing and other organic materials are transparent to millimeter waves of certain frequencies, so a recent application has been scanners to detect weapons and other dangerous objects carried under clothing, for applications such as airport security.[16] Privacy advocates are concerned about the use of this technology because, in some cases, it allows screeners to see airport passengers as if without clothing.

The TSA has deployed millimeter wave scanners to many major airports.

Prior to a software upgrade the technology did not mask any part of the bodies of the people who were being scanned. However, passengers' faces were deliberately masked by the system. The photos were screened by technicians in a closed room, then deleted immediately upon search completion. Privacy advocates are concerned. "We're getting closer and closer to a required strip-search to board an airplane," said Barry Steinhardt of the American Civil Liberties Union.[17] To address this issue, upgrades have eliminated the need for an officer in a separate viewing area. The new software generates a generic image of a human. There is no anatomical differentiation between male and female on the image, and if an object is detected, the software only presents a yellow box in the area. If the device does not detect anything of interest, no image is presented.[18] Passengers can decline scanning and be screened via a metal detector and patted down.[19]

According to Farran Technologies, a manufacturer of one model of the millimeter wave scanner, the technology exists to extend the search area to as far as 50 meters beyond the scanning area which would allow security workers to scan a large number of people without their awareness that they are being scanned.[20]

Thickness gauging

Recent studies at the University of Leuven have proven that millimeter waves can also be used as a non-nuclear thickness gauge in various industries. Millimeter waves provide a clean and contact-free way of detecting variations in thickness. Practical applications for the technology focus on

paper manufacturing, glass production and mineral wool production
.

Medicine

Low

GHz.[22] This type of treatment may be called millimeter wave therapy or extremely high frequency therapy.[23] This treatment is associated with eastern European nations (e.g., former USSR nations).[21] The Russian Journal Millimeter waves in biology and medicine studies the scientific basis and clinical applications of millimeter wave therapy.[24]

Police speed radar

Traffic police use speed-detecting

radar guns in the Ka-band (33.4–36.0 GHz).[25]

See also

References

  1. List of IEEE milestones. Institute of Electrical and Electronics Engineers
    . 14 June 2022.
  2. ^ User Equipment (UE) radio transmission and reception; Part 3: Range 1 and Range 2 Interworking operation with other radios (PDF) (Technical Specification). 3GPP TS 38.101-3 version 15.2.0 Release 15. ETSI. July 2018. p. 11. Retrieved 5 December 2019.
  3. ISBN 978-3-319-62166-1
    .
  4. ^
    ISBN 978-1-118-10275-6
    .
  5. ^ a b c "Millimeter Wave Propagation: Spectrum Management Implications" (PDF). Office of Engineering and Technology, Bulletin No. 70. Federal Communications Commission (FCC), US Dept. of Commerce. July 1997. Retrieved May 20, 2017.
  6. ^
    ISBN 978-3-319-35068-4
    .
  7. ISBN 0-471-74368-2
    .
  8. ^ FCC.gov[permanent dead link], Comments of IEEE Geoscience and Remote Sensing Society, FCC RM-11104, 10/17/07
  9. RF Design
    , May 2006
  10. ISSN 2169-3536
    .
  11. ^ Asadi, Arash; Klos, Sabrina; Sim, Gek Hong; Klein, Anja; Hollick, Matthias (2018-04-15). "FML: Fast Machine Learning for 5G mmWave Vehicular Communications". IEEE Infocom'18.
  12. S2CID 12358456
    .
  13. ^ "Slideshow: Say Hello to the Goodbye Weapon". Wired. 5 December 2006. Retrieved 16 August 2016.
  14. ^ "Active Denial System: a terahertz based military deterrent for safe crowd control". Terasense Group Inc. 2019-05-29. Retrieved 2020-05-03.
  15. ^ Hambling, David (2009-05-08). "'Pain ray' first commercial sale looms". Wired. Retrieved 2020-05-03.
  16. ^ Newscientisttech.com Archived March 11, 2007, at the Wayback Machine
  17. ^ Frank, Thomas (18 February 2009). "Body scanners replace metal detectors in tryout at Tulsa airport". USA Today. Retrieved 2 May 2010.
  18. ^ "Statement of Robert Kane to House of Representatives" (PDF). 2011-11-03. p. 2. Archived from the original (PDF) on 2011-11-25.
  19. ^ Cortez, Joe. "The Three Inspection Options at TSA Checkpoints". Trip Savvy. Retrieved 11 January 2024.
  20. ^ esa. "Bat inspires space tech for airport security". esa.int. Retrieved 7 April 2018.
  21. ^
    S2CID 22730643
    .
  22. PMID 10999395
    .
  23. PMID 9519213
    .
  24. ^ Benran.ru Archived 2011-07-18 at the Wayback Machine
  25. ^ "Radio and Radar Frequency Bands". copradar.com. Retrieved 30 April 2020.

External links

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