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54-519: The specification was finalized in January 2008. The WirelessHD specification is based on a 7 GHz channel in the 60 GHz Extremely High Frequency radio band. It allows either lightly compressed (proprietary wireless link-aware codec) or uncompressed digital transmission of high-definition video and audio and data signals, essentially making it equivalent of a wireless HDMI . First-generation implementation achieves data rates from 4 Gbit/s, but

108-475: 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. 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

162-429: A few kilometers. Thus, they are useful for densely packed communications networks such as personal area networks that improve spectrum utilization through frequency reuse . Millimeter waves show "optical" propagation characteristics and can be reflected and focused by small metal surfaces and dielectric lenses around 5 to 30 cm (2 inches to 1 foot) diameter. Because their wavelengths are often much smaller than

216-397: A more rigorous definition of the beam width has to be used: and This definition also incorporates information about x – y correlation ⟨ x y ⟩ {\displaystyle \langle xy\rangle } , but for circular symmetric beams, both definitions are the same. Some new symbols appeared within the formulas, which are the first- and second-order moments:

270-494: A significant number of pixels at the edges of the sensor that register a small baseline value (the background value). If the baseline value is large or if it is not subtracted out of the image, then the computed D4σ value will be larger than the actual value because the baseline value near the edges of the sensor are weighted in the D4σ integral by x . Therefore, baseline subtraction is necessary for accurate D4σ measurements. The baseline

324-757: A small 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 frequency ranges near the bottom of the band are being used in the newest generation of cell phone networks, 5G networks. 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. Millimeter waves propagate solely by line-of-sight paths. They are not refracted by

378-424: 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. 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

432-420: Is ⁠ 1 / 2 ⁠ (−3 dB ), in which case the diameter obtained is the full width of the beam at half its maximum intensity (FWHM). This is also called the half-power beam width (HPBW). The 1/e width is equal to the distance between the two points on the marginal distribution that are 1/e = 0.135 times the maximum value. In many cases, it makes more sense to take the distance between points where

486-473: Is a concern to video copyright owners. The WirelessHD specification has provisions for content encryption via Digital Transmission Content Protection (DTCP) as well as provisions for network management. A standard remote control allows users to control the WirelessHD devices and choose which device will act as the source for the display. WirelessHD competes with WiGig in some applications. WiGig transmits in

540-428: Is a large broadband that span a radius of about (3 GHz to 300 GHz ) for the molecular spectra of radio frequencies . It lies between the super high frequency (300 mHz to 3 GHz) band and the far infrared band (300 GHz to 10 ), for which the lower part 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

594-437: 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. Compared to lower bands, radio waves in this band have high atmospheric attenuation : they are absorbed by the gases in the atmosphere. Absorption increases with frequency until at

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648-519: Is chosen because a circular Gaussian beam profile integrated down to 1/e of its peak value contains 86% of its total power. The D86 width is often used in applications that are concerned with knowing exactly how much power is in a given area. For example, applications of high-energy laser weapons and lidars require precise knowledge of how much transmitted power actually illuminates the target. The definition given before holds for stigmatic (circular symmetric) beams only. For astigmatic beams, however,

702-505: Is easily measured by recording the average value for each pixel when the sensor is not illuminated. The D4σ width, unlike the FWHM and 1/e widths, is meaningful for multimodal marginal distributions — that is, beam profiles with multiple peaks — but requires careful subtraction of the baseline for accurate results. The D4σ is the ISO international standard definition for beam width. Before the advent of

756-412: 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. Passengers can decline scanning and be screened via a metal detector and patted down. According to Farran Technologies, a manufacturer of one model of the millimeter wave scanner,

810-454: Is particularly associated with the range of 40–70 GHz . This type of treatment may be called millimeter wave therapy or extremely high frequency therapy . This treatment is associated with eastern European nations (e.g., former USSR nations). The Russian Journal Millimeter waves in biology and medicine studies the scientific basis and clinical applications of millimeter wave therapy. Traffic police use speed-detecting radar guns in

864-401: Is the centroid of the beam profile in the x direction. When a beam is measured with a laser beam profiler , the wings of the beam profile influence the D4σ value more than the center of the profile, since the wings are weighted by the square of its distance, x , from the center of the beam. If the beam does not fill more than a third of the beam profiler's sensor area, then there will be

918-404: Is the diameter along any specified line that is perpendicular to the beam axis and intersects it. Since beams typically do not have sharp edges, the diameter can be defined in many different ways. Five definitions of the beam width are in common use: D4σ , 10/90 or 20/80 knife-edge , 1/e , FWHM , and D86 . The beam width can be measured in units of length at a particular plane perpendicular to

972-400: Is the full width of the beam at 1/e . The D4σ width of a beam in the horizontal or vertical direction is 4 times σ, where σ is the standard deviation of the horizontal or vertical marginal distribution respectively. Mathematically, the D4σ beam width in the x dimension for the beam profile I ( x , y ) {\displaystyle I(x,y)} is expressed as where

1026-542: 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,

1080-603: The 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. 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

1134-457: The CCD beam profiler, the beam width was estimated using the knife-edge technique: slice a laser beam with a razor and measure the power of the clipped beam as a function of the razor position. The measured curve is the integral of the marginal distribution, and starts at the total beam power and decreases monotonically to zero power. The width of the beam is defined as the distance between the points of

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1188-568: The ionosphere nor do they travel along the Earth as ground waves as lower frequency radio waves do. At typical power densities they are blocked by building walls and suffer significant attenuation passing through foliage. Absorption by atmospheric gases is a significant factor throughout the band and increases with frequency. However, this absorption is maximum at a few specific absorption lines , mainly those of oxygen at 60 GHz and water vapor at 24 GHz and 184 GHz. At frequencies in

1242-484: The upper atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The International Telecommunication Union non-exclusive passive frequency allocation at 57–59.3 GHz 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. Currently operational U.S. satellite sensors such as

1296-446: The wavelength . Beam diameter usually refers to a beam of circular cross section, but not necessarily so. A beam may, for example, have an elliptical cross section, in which case the orientation of the beam diameter must be specified, for example with respect to the major or minor axis of the elliptical cross section. The term "beam width" may be preferred in applications where the beam does not have circular symmetry. The angle between

1350-418: The "windows" between these absorption peaks, millimeter waves have much less atmospheric attenuation and greater range, so many applications use these frequencies. Millimeter wavelengths are the same order of size as raindrops , so precipitation causes additional attenuation due to scattering ( rain fade ) as well as absorption. The high free space loss and atmospheric absorption limit useful propagation to

1404-417: The 1/e width only depend on three points on the marginal distribution, unlike D4σ and knife-edge widths that depend on the integral of the marginal distribution. 1/e width measurements are noisier than D4σ width measurements. For multimodal marginal distributions (a beam profile with multiple peaks), the 1/e width usually does not yield a meaningful value and can grossly underestimate the inherent width of

1458-589: The 10/90 or 20/80 knife-edge width is a useful metric when the user wishes to be sure that the width encompasses a fixed fraction of total beam power. Most CCD beam profiler's software can compute the knife-edge width numerically. The main drawback of the knife-edge technique is that the measured value is displayed only on the scanning direction, minimizing the amount of relevant beam information. To overcome this drawback, an innovative technology offered commercially allows multiple directions beam scanning to create an image like beam representation. By mechanically moving

1512-450: 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 Wi-Fi standards IEEE 802.11ad and IEEE 802.11ay operate in the 60 GHz ( V band ) spectrum to achieve data transfer rates as high as 7 Gbit/s and at least 20 Gbit/s , respectively. Uses of

1566-774: The Ka-band (33.4–36.0 GHz). 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 Beamwidth The beam diameter or beam width of an electromagnetic beam

1620-552: The WirelessHD specification ameliorates this limitation through the use of beam forming at the receiver and transmitter antennas to increase the signal's effective radiated power , find the best path, and utilise wall reflections. The goal range for the first products will be in-room, point-to-point , non line-of-sight (NLOS) at up to 10 meters. The atmospheric absorption of 60 GHz energy by oxygen molecules limits undesired propagation over long distances and helps control intersystem interference and long distance reception, which

1674-404: The beam axis, but it can also refer to the angular width, which is the angle subtended by the beam at the source. The angular width is also called the beam divergence . Beam diameter is usually used to characterize electromagnetic beams in the optical regime, and occasionally in the microwave regime, that is, cases in which the aperture from which the beam emerges is very large with respect to

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1728-602: The beam diameter as the distance between diametrically opposed points in that cross-section of a beam where the power per unit area is 1/e (0.368) times that of the peak power per unit area. This is the beam diameter definition that is used for computing the maximum permissible exposure to a laser beam. In addition, the Federal Aviation Administration also uses the 1/e definition for laser safety calculations in FAA Order JO 7400.2, Para. 29-1-5d. Measurements of

1782-407: The beam power and Using this general definition, also the beam azimuthal angle ϕ {\displaystyle \phi } can be expressed. It is the angle between the beam directions of minimal and maximal elongations, known as principal axes, and the laboratory system, being the x {\displaystyle x} and y {\displaystyle y} axes of

1836-580: 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), and a smaller law enforcement version, called Silent Guardian that was developed by Raytheon later, had an output power of 30 kW. 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. Privacy advocates are concerned about

1890-611: The beam. For multimodal distributions, the D4σ width is a better choice. For an ideal single-mode Gaussian beam, the D4σ, D86 and 1/e width measurements would give the same value. For a Gaussian beam, the relationship between the 1/e width and the full width at half maximum is 2 w = 2   F W H M ln ⁡ 2 = 1.699 × F W H M {\displaystyle 2w={\frac {{\sqrt {2}}\ \mathrm {FWHM} }{\sqrt {\ln 2}}}=1.699\times \mathrm {FWHM} } , where 2 w {\displaystyle 2w}

1944-450: The circle that is centered at the centroid of the beam profile and contains 86% of the beam power. The solution for D86 is found by computing the area of increasingly larger circles around the centroid until the area contains 0.86 of the total power. Unlike the previous beam width definitions, the D86 width is not derived from marginal distributions. The percentage of 86, rather than 50, 80, or 90,

1998-551: The core technology allows theoretical data rates as high as 25 Gbit/s (compared to 10.2 Gbit/s for HDMI 1.3 and 21.6 Gbit/s for DisplayPort 1.2), permitting WirelessHD to scale to higher resolutions, color depth, and range. The 1.1 version of the specification increases the maximum data rate to 28 Gbit/s, supports common 3D formats, 4K resolution, WPAN data, low-power mode for portable devices, and HDCP 2.0 content protection. The 60 GHz band usually requires line of sight between transmitter and receiver , and

2052-410: The detector and given by International standard ISO 11146-1:2005 specifies methods for measuring beam widths (diameters), divergence angles and beam propagation ratios of laser beams (if the beam is stigmatic) and for general astigmatic beams ISO 11146-2 is applicable. The D4σ beam width is the ISO standard definition and the measurement of the M beam quality parameter requires the measurement of

2106-507: The equipment that manipulates them, the techniques of geometric optics can be used. Diffraction is less than at lower frequencies, although millimeter waves can be diffracted by building edges. At millimeter wavelengths, surfaces appear rougher so diffuse reflection increases. Multipath propagation , particularly reflection from indoor walls and surfaces, causes serious fading. Doppler shift of frequency can be significant even at pedestrian speeds. In portable devices, shadowing due to

2160-535: 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. 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 remote sensing near 60 GHz can determine temperature in

2214-717: The intensity falls to 1/e = 0.135 times the maximum value. If there are more than two points that are 1/e times the maximum value, then the two points closest to the maximum are chosen. The 1/e width is important in the mathematics of Gaussian beams , in which the intensity profile is described by I ( r ) = I 0 ( w 0 w ) 2 exp ( − 2 r 2 w 2 ) {\displaystyle I(r)=I_{0}\left({\frac {w_{0}}{w}}\right)^{2}\exp \!\left(\!-2{\frac {r^{2}}{w^{2}}}\right)} . The American National Standard Z136.1-2007 for Safe Use of Lasers (p. 6) defines

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2268-418: The knife edge across the beam, the amount of energy impinging the detector area is determined by the obstruction. The profile is then measured from the knife-edge velocity and its relation to the detector's energy reading. Unlike other systems, a unique scanning technique uses several different oriented knife-edges to sweep across the beam. By using tomographic reconstruction , mathematical processes reconstruct

2322-452: The laser beam size in different orientations to an image similar to the one produced by CCD cameras. The main advantage of this scanning method is that it is free from pixel size limitations (as in CCD cameras) and allows beam reconstructions with wavelengths not usable with existing CCD technology. Reconstruction is possible for beams in deep UV to far IR. The D86 width is defined as the diameter of

2376-458: The maximum peak of radiated power and the first null (no power radiated in this direction) is called the Rayleigh beamwidth. The simplest way to define the width of a beam is to choose two diametrically opposite points at which the irradiance is a specified fraction of the beam's peak irradiance, and take the distance between them as a measure of the beam's width. An obvious choice for this fraction

2430-414: The measured curve that are 10% and 90% (or 20% and 80%) of the maximum value. If the baseline value is small or subtracted out, the knife-edge beam width always corresponds to 60%, in the case of 20/80, or 80%, in the case of 10/90, of the total beam power no matter what the beam profile. On the other hand, the D4σ, 1/e , and FWHM widths encompass fractions of power that are beam-shape dependent. Therefore,

2484-444: 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. In addition, use of millimeter wave bands for vehicular communication is also emerging as an attractive solution to support (semi-)autonomous vehicular communications. Shorter wavelengths in this band permit

2538-517: 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. 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

2592-489: The same 60 GHz band used by WirelessHD. ip based: port / cable standards for mobile equipment: Extremely high frequency Extremely high frequency is the International Telecommunication Union designation specifically included in the electromagnetic spectrum classification group with 8 other principal dedicated channel allocation. Extremely high frequency or commonly known as "EHF",

2646-403: The stream of outgoing bullets as well as the target, allowing the computer fire control system to change the aim to bring them together. With Raytheon the 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). The weapon causes a person in

2700-541: 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. 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

2754-519: The technology focus on plastics extrusion , paper manufacturing , glass production and mineral wool production . Low intensity (usually 10 mW/cm or less) electromagnetic radiation of extremely high frequency may be used in human medicine for the treatment of diseases . For example, "A brief, low-intensity MMW exposure can change cell growth and proliferation rates, activity of enzymes , state of cell genetic apparatus, function of excitable membranes and peripheral receptors." This treatment

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2808-410: The top end of the band the waves are attenuated to zero within a few meters. Absorption by humidity in the atmosphere is significant except in desert environments, and attenuation by rain ( rain fade ) is a serious problem even over short distances. However the short propagation range allows smaller frequency reuse distances than lower frequencies. The short wavelength allows modest size antennas to have

2862-400: 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,

2916-423: 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

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