Extremely high frequency

The EHF band has commonly been used in radio astronomy and remote sensing. Ground-based radio astronomy has been limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter ArrayAtacama Large Millimeter Array (ALMA) due to atmospheric absorption issues. Satellite-based remote sensing near 60 GHz have been used to determine temperature distributions in the upper atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The International Telecommunication Union (ITU) nonexclusive passive frequency allocation at 57-59.3 is used for atmospheric monitoring in meteorological and climate sensing applications, and is important for these purposes due to the properties of oxygen absorption and emission in Earth's atmosphere.

EHF waves are prone to atmospheric attenuation, making them of little use over long distances. The radio waves in the EHF band, or millimeter band, are absorbed by gases in the atmosphere, which reduces their range, and has made them best suited for short range terrestrial communication over about a kilometer. They mainly propagate solely by line-of-sight paths, and are not reflected by the ionosphere nor do they travel along the Earth as ground waves. At typical power densities, they are blocked by building walls and suffer significant attenuation passing through foliage.

In addition, because of the shorter wavelengths this band permits, it offers a chance to use smaller antennas that can achieve high directivity and high gain. This allows for a more efficient use of frequencies for point-to-multipoint applications, which means a greater number of directive antennas can be placed in a given area, and offer a higher density of users due to a greater frequency reuse. This allows the EHF band to serve some applications that would otherwise use fiber-optic communications, for very short links such as a circuit board, and for vehicular communication for semi-autonomous or fully-autonomous vehicular communication.

The LIMS system is a signal processor integrated with a coherent, solid-sate 94 GHz transceiver having a 1 GHz instantaneous bandwidth. The sensor's waveform offers good range resolution and uses a high duty cycle for extended range detection compatible with peak power limitations of MMW solid-state sources. These systems are capable of being carried on various weapon systems, and can be used for stationary target discrimination and classification, as well as target tracking and weapon aiming.

Further, the United States Air Force has been reported to have used extremely high frequency bands to develop a nonlethal weapon systems called Active Denial System (ADS), which emits a beam of radiation with a wavelength of 3 mm. The weapon is reportedly not painful, but makes the target feel as if their clothes will catch fire. The military version of this anti-personnel weapon has an output power of 100 kilowatts (kW) while a smaller version of the system intended for use by law enforcement, also known as the Silent Guardian, has an output power of 30 kW.

For massive machine-type communication (mMTC), in combination with IoT technologiesIoT technologies, which require low power consumption and low data rates for large numbers of connected services, mMTC and the use of mmWaves offers long-range communication with energy efficiency and asynchronous access. And in the case of ultra-reliable and low-latency communications (URLLC), mmWaves can be used to cater to safety-critical and mission-critical applications of 5G, such as industrial automation and robotics, autonomous driving, drone-based delivery, and remote medical assistance.

The EHF band has commonly been used in radio astronomy and remote sensing. Ground-based radio astronomy has been limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter Array (ALMA) due to atmospheric absorption issues. Satellite-based remote sensing near 60 GHz have been used to determine temperature distributions in the upper atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The International Telecommunication UnionInternational Telecommunication Union (ITU) nonexclusive passive frequency allocation at 57-59.3 is used for atmospheric monitoring in meteorological and climate sensing applications, and is important for these purposes due to the properties of oxygen absorption and emission in Earth's atmosphere.

EHF waves are prone to atmospheric attenuation, making them of little use over long distances. The radio waves in the EHF band, or millimeter band, are absorbed by gases in the atmosphere, which reduces their range, and has made them best suited for short range terrestrial communication over about a kilometer. They mainly propagate solely by line-of-sight paths, and are not reflected by the ionosphere nor do they travel along the EarthEarth as ground waves. At typical power densities, they are blocked by building walls and suffer significant attenuation passing through foliage.

Shallow machine learning algorithms have been applied to the design of intelligent antenna systems, reliable radio propagation models, and spectrum usage prediction techniques, and in these cases the use of machine learning has shown superior performance compared to traditional approaches. In the case of mmWave, or EHF, these frequencies can support high communication rates, and facilitate the use of multiple-input-multiple-output (MIMOMIMO) techniques to increase wireless capacity. However, MIMO technology can result in path loss and channel uncertainty and has a high energy consumption cost. The use of machine learning could provide an opportunity for channel modeling and offer greater reliability in mmWave devices. Further, the application of machine learning could be used to optimize frequencies to reduce atmospheric propagation loss and increase the overall range of mmWave devices.

In the case of the United States Air Force's Advanced Extremely High FrequencyAdvanced Extremely High Frequency (AEHF) satellite systems, the systems have used super high-frequency (SHF) for long range communications and to help with tropospheric impairments. The AEHF is a next-generation military strategic and tactical satellite relay system, which is intended to provide survivable, protected communications to U.S. Forces and selected allies worldwide, that would consist of four crosslinked satellites, a ground mission control and user terminals.

Further, the United States Air ForceUnited States Air Force has been reported to have used extremely high frequency bands to develop a nonlethal weapon systems called Active Denial System (ADS) which emits a beam of radiation with a wavelength of 3 mm. The weapon is reportedly not painful, but makes the target feel as if their clothes will catch fire. The military version of this anti-personnel weapon has an output power of 100 kilowatts (kW) while a smaller version of the system intended for use by law enforcement, also known as the Silent Guardian, has an output power of 30 kW.

For many radio wave frequencies and their propagation, which is largely affected by environmental and climatic factors which impact the performance of radio communication systems, availability and reliability of those systems, and the use of congested electromagnetic systems, have pushed towards the development of flexible solutions to solve these challenges. Instead of, what has been previously used, explicit programming for these challenges, machine learningmachine learning has been proposed as a solution, as the model can be trained and can continue to learn from data and make inferences on new observations.

Extremely high frequency (EHF) is the designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 GHz, lying between the high frequency bandfrequency band and the far infrared band, which is the lower part of terahertz band. Radio waves in this band have wavelengths from ten to one millimeter, and are therefore also called millimeter band and radiation in this band is called millimeter waves (mmWaves). Millimeter-length electromagnetic waves were first investigated by Indian physicist Jagadish Chandra Bose during 1894-1896, when he reached up to 60 GHz in his experiments.

Another development of mmWave has been its use in security applications. This is capable as clothing and other organic materials are translucent in some mmWave atmospheric windows. This would allow an airport or related travel terminal to screen groups or passengers and individuals using mmWave beams and see if they are carrying or hiding anything on their person without having to search them. PrivacyPrivacy advocates have raised concerns about the use of this technology, as people are seen without clothing, but most applications remove the face and other identifying features during a scan. These systems have been installed in airports in the United States and in Amsterdam.

The EHF band has commonly been used in radio astronomy and remote sensing. Ground-based radio astronomy has been limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter Array (ALMAALMA) due to atmospheric absorption issues. Satellite-based remote sensing near 60 GHz have been used to determine temperature distributions in the upper atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The International Telecommunication Union (ITU) nonexclusive passive frequency allocation at 57-59.3 is used for atmospheric monitoring in meteorological and climate sensing applications, and is important for these purposes due to the properties of oxygen absorption and emission in Earth's atmosphere.

The EHF band has commonly been used in radio astronomy and remote sensing. Ground-based radio astronomy has been limited to high altitude sites such as Kitt PeakKitt Peak and Atacama Large Millimeter Array (ALMA) due to atmospheric absorption issues. Satellite-based remote sensing near 60 GHz have been used to determine temperature distributions in the upper atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The International Telecommunication Union (ITU) nonexclusive passive frequency allocation at 57-59.3 is used for atmospheric monitoring in meteorological and climate sensing applications, and is important for these purposes due to the properties of oxygen absorption and emission in Earth's atmosphere.

The EHF band has commonly been used in radio astronomyradio astronomy and remote sensing. Ground-based radio astronomy has been limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter Array (ALMA) due to atmospheric absorption issues. Satellite-based remote sensing near 60 GHz have been used to determine temperature distributions in the upper atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The International Telecommunication Union (ITU) nonexclusive passive frequency allocation at 57-59.3 is used for atmospheric monitoring in meteorological and climate sensing applications, and is important for these purposes due to the properties of oxygen absorption and emission in Earth's atmosphere.

Extremely high frequency (EHF) is the designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 GHz, lying between the high frequency band and the far infrared band, which is the lower part of terahertz band. Radio waves in this band have wavelengths from ten to one millimeter, and are therefore also called millimeter band and radiation in this band is called millimeter waves (mmWaves). Millimeter-length electromagnetic waves were first investigated by Indian physicist Jagadish Chandra BoseJagadish Chandra Bose during 1894-1896, when he reached up to 60 GHz in his experiments.