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Encyclopedia > Radar
This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll.
This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll.[1]

Radar is a system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. A transmitter emits radio waves, which are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the radio signal returned is usually very weak, radio signals can easily be amplified. This enables a radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation, air traffic control, police detection of speeding traffic, and by the military. It was originally called RDF (Radio Direction Finder) in Britain. The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. The term has since entered the English language as a standard word, radar, losing the capitalization in the process. Look up radar in Wiktionary, the free dictionary. ... Download high resolution version (546x697, 80 KB)The only information given by the source about this image is Radar. We can deduce a few more things from this image: The dish rotates on a circular track The facility is in the tropics (because of palm trees) The dish is approximately... Download high resolution version (546x697, 80 KB)The only information given by the source about this image is Radar. We can deduce a few more things from this image: The dish rotates on a circular track The facility is in the tropics (because of palm trees) The dish is approximately... A yagi antenna Most simply, an antenna is an electronic component designed to send or receive radio waves. ... An anti-ballistic missile (ABM) is a missile designed to counter ballistic missiles. ... Kwajalein infrastructure and RTS headquarters, click to enlarge. ... Kwajalein Atoll - NASA NLT Landsat 7 (Visible Color) Satellite Image Kwajalein Atoll (Marshallese: Kuwajleen) is part of the Republic of the Marshall Islands (RMI). ... Portion of a Pacific atoll showing two islets on the ribbon or barrier reef separated by a deep pass between the ocean and the lagoon. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... “Flying Machine” redirects here. ... Radio waves are electromagnetic waves occurring on the radio frequency portion of the electromagnetic spectrum. ... Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... // Meteorology (from Greek: μετέωρον, meteoron, high in the sky; and λόγος, logos, knowledge) is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting. ... For the Canadian musical group, see Air Traffic Control (band). ... A speed limit is the maximum speed allowed by law by vehicles on a road. ... This article needs additional references or sources for verification. ... Look up acronym, initialism, alphabetism in Wiktionary, the free dictionary. ...

Contents

History

Main article: History of radar

Several inventors, scientists, and engineers contributed to the development of radar. The first to use radio waves to detect "the presence of distant metallic objects via radio waves" was Christian Hülsmeyer,[2][3] who in 1904 demonstrated the feasibility of detecting the presence of a ship in dense fog, but not its distance. He received Reichspatent Nr. 165546 for his pre-radar device in April, and patent 169154 on November 11 for a related amendment. He also received a patent (GB13170) in England for his telemobiloscope on September 22, 1904.[2][4] The history of radar began in the 1900s when engineers invented reflection devices. ... For other uses, see Inventor (disambiguation). ... Look up engineer in Wiktionary, the free dictionary. ... The history of radar began in the 1900s when engineers invented reflection devices. ... November 11 is the 315th day of the year (316th in leap years) in the Gregorian calendar, with 50 days remaining. ... is the 265th day of the year (266th in leap years) in the Gregorian calendar. ... 1904 (MCMIV) was a leap year starting on a Friday (see link for calendar). ...


Nikola Tesla, in August 1917, first established principles regarding frequency and power level for the first primitive radar units.[1] Nikola Tesla (1856-1943)[1] was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ...


Before the Second World War, developments by the Americans (Dr. Robert M. Page tested the first monopulse radar in 1934),[5] the Germans, the French (French Patent n° 788795 in 1934),[6] and the British (British Patent GB593017 by Robert Watson-Watt in 1935),[6][7] led to the first real radars. Hungarian Zoltán Bay produced a working model by 1936 at the Tungsram laboratory in the same vein. Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ... Monopulse radars are an adaptation of conical scanning radars which send additional information in the radar signal in order to avoid problems caused by rapid changes in signal strength. ... Sir Robert Alexander Watson-Watt, ca. ... Zoltán Lajos Bay (1900 – 1992) was a Hungarian physicist. ... Tungsram is a Hungarian manufacturer of light bulbs and vacuum tubes since 1896, now a subsidiary of General Electric and used as a brand name only. ...


In 1934, Émile Girardeau, working with the first French radar systems, stated he was building radar systems "conceived according to the principles stated by Tesla".[2]


The war precipitated research to find better resolution, more portability and more features for the new defence technology. Post-war years have seen the use of radar in fields as diverse as air traffic control, weather monitoring, astrometry and road speed control. For the Canadian musical group, see Air Traffic Control (band). ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ...


Principles

Reflection

Brightness can indicate reflectivity as in this 1960 weather radar image. The radar's frequency, pulse form, and antenna largely determine what it can observe.
Brightness can indicate reflectivity as in this 1960 weather radar image. The radar's frequency, pulse form, and antenna largely determine what it can observe.

Electromagnetic waves reflect (scatter) from any large change in the dielectric or diamagnetic constants. This means that a solid object in air or a vacuum, or other significant change in atomic density between the object and what's surrounding it, will usually scatter radar (radio) waves. This is particularly true for electrically conductive materials, such as metal and carbon fibre, making radar particularly well suited to the detection of aircraft and ships. Radar absorbing material, containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection. This is the radio equivalent of painting something a dark color. Download high resolution version (1088x1172, 288 KB)From http://www. ... Download high resolution version (1088x1172, 288 KB)From http://www. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... A dielectric, or electrical insulator, is a substance that is highly resistant to electric current. ... Diamagnetism is a very weak form of magnetism that is only exhibited in the presence of an external magnetic field. ... Layers of Atmosphere—not to scale (NOAA) [1] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Look up Vacuum in Wiktionary, the free dictionary. ... Conduction is the movement of electrically charged particles through a transmission medium (electrical conductor). ... Carbon fiber composite is a strong, light and very expensive material. ... “Flying Machine” redirects here. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... For other senses of this word, see magnetism (disambiguation). ...


Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of the target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror. If the wavelength is much longer than the size of the target, the target is polarized (positive and negative charges are separated), like a dipole antenna. This is described by Rayleigh scattering, an effect that creates the Earth's blue sky and red sunsets. When the two length scales are comparable, there may be resonances. Early radars used very long wavelengths that were larger than the targets and received a vague signal, whereas some modern systems use shorter wavelengths (a few centimetres or shorter) that can image objects as small as a loaf of bread. A mirror, reflecting a vase. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... A simple half-wave dipole antenna that a shortwave listener might build. ... Rayleigh scattering causing the blue hue of the sky and the reddening at sunset Rayleigh scattering (named after Lord Rayleigh) is the scattering of light, or other electromagnetic radiation, by particles much smaller than the wavelength of the light. ... A composite image showing the terminator dividing night from day, running across Europe and Africa. ... This article is about resonance in physics. ... The wavelength is the distance between repeating units of a wave pattern. ... The wavelength is the distance between repeating units of a wave pattern. ... A centimetre (American spelling centimeter, symbol cm) is a unit of length that is equal to one hundredth of a metre, the current SI base unit of length. ...


Short radio waves reflect from curves and corners, in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between the reflective surfaces. A structure consisting of three flat surfaces meeting at a single corner, like the corner on a box, will always reflect waves entering its opening directly back at the source. These so-called corner reflectors are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect, and are often found on boats in order to improve their detection in a rescue situation and to reduce collisions. For similar reasons, objects attempting to avoid detection will angle their surfaces in a way to eliminate inside corners and avoid surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft. These precautions do not completely eliminate reflection because of diffraction, especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff, are very reflective but do not direct the scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross section. The reflection of a bridge in Indianapolis, Indianas Central Canal. ... Buoy in San Diego Harbor. ... This article or section is in need of attention from an expert on the subject. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ... Modern US Navy RR-129 and RR-124 chaff countermeasures and containers Chaff, originally called Window by the British, and Düppel by the WWII era German Luftwaffe, is a radar countermeasure in which aircraft or other targets spread a cloud of small, thin pieces of aluminium, metallised glass fibre... Typical RCS diagram (B-26 Invader) Radar cross section (RCS) describes the extent to which an object reflects an incident electromagnetic wave. ...


Radar equation

The amount of power Pr returning to the receiving antenna is given by the radar equation:

P_r = {{P_t G_t A_r sigma F^4}over{{(4pi)}^2 R_t^2R_r^2}}

where

  • Pt = transmitter power
  • Gt = gain of the transmitting antenna
  • Ar = effective aperture (area) of the receiving antenna
  • σ = radar cross section, or scattering coefficient, of the target
  • F = pattern propagation factor
  • Rt = distance from the transmitter to the target
  • Rr = distance from the target to the receiver.

In the common case where the transmitter and the receiver are at the same location, Rt = Rr and the term Rt2 Rr2 can be replaced by R4, where R is the range. This yields: Typical RCS diagram (B-26 Invader) Radar cross section (RCS) describes the extent to which an object reflects an incident electromagnetic wave. ...

P_r = {{P_t G_t A_r sigma F^4}over{{(4pi)}^2 R^4}}

This shows that the received power declines as the fourth power of the range, which means that the reflected power from distant targets is very, very small.


The equation above with F = 1 is a simplification for vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects should also be considered. Look up Vacuum in Wiktionary, the free dictionary. ... PRIMERGY MultiPath PRIMERGY MultiPath supports redundant Fiber Channel paths, the configured connections between server and subsystem that are such an important component of disaster-tolerant servers and clusters. ... Pathloss is a term used in radio communications to denote the radio wave propagation losses taking place on the signals path from the transmitter to the receiver. ...


Other mathematical developments in radar signal processing include time-frequency analysis (Weyl Heisenberg or wavelet), as well as the chirplet transform which makes use of the fact that radar returns from moving targets typically "chirp" (change their frequency as a function of time, as does the sound of a bird or bat). A time-frequency representation (TFR) is a view of a signal (taken to be a function of time) represented over both time and frequency. ... A wavelet is a kind of mathematical function used to divide a given function into different frequency components and study each component with a resolution that matches its scale. ... Comparison of wave, wavelet, chirp, and chirplet In signal processing, the chirplet transform is an inner product of an input signal with a family of analysis primitives called chirplets. ...


Polarization

In the transmitted radar signal, the electric field is perpendicular to the direction of propagation, and this direction of the electric field is the polarization of the wave. Radars use horizontal, vertical, linear and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate a fractal surface, such as rocks or soil, and are used by navigation radars. In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... In electrodynamics, circular polarization of electromagnetic radiation is a polarization such that the tip of the electric field vector, at a fixed point in space, describes a circle as time progresses. ... In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation. ... Random redirects here. ... The boundary of the Mandelbrot set is a famous example of a fractal. ... Table of geography, hydrography, and navigation, from the 1728 Cyclopaedia. ...


Interference

Radar systems must overcome several different sources of unwanted signals in order to focus only on the actual targets of interest. These unwanted signals may originate from internal and external sources, both passive and active. The ability of the radar system to overcome these unwanted signals defines its signal-to-noise ratio (SNR): the higher a system's SNR, the better it is in isolating actual targets from the surrounding noise signals. Signal-to-noise ratio (often abbreviated SNR or S/N) is an electrical engineering concept defined as the ratio of a signal power to the noise power corrupting the signal. ...


Noise

Signal noise is an internal source of random variations in the signal, which is inherently generated to some degree by all electronic components. Noise typically appears as random variations superimposed on the desired echo signal received in the radar receiver. The lower the power of the desired signal, the more difficult it is to discern it from the noise (similar to trying to hear a whisper while standing near a busy road). Therefore, the most important noise sources appear in the receiver and much effort is made to minimize these factors. Noise figure is a measure of the noise produced by a receiver compared to an ideal receiver, and this needs to be minimized. In science, and especially in physics and telecommunication, noise is fluctuations in and the addition of external factors to the stream of target information (signal) being received at a detector. ... In telecommunication, noise figure (NF) is the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard noise temperature (usually 290 K). ...


Noise is also generated by external sources, most importantly the natural thermal radiation of the background scene surrounding the target of interest. In modern radar systems, due to the high performance of their receivers, the internal noise is typically about equal to or lower than the external scene noise. An exception is if the radar is aimed upwards at clear sky, where the scene is so cold that it generates very little thermal noise. Johnson-Nyquist noise (sometimes thermal noise, Johnson noise or Nyquist noise) is the noise generated by the equilibrium fluctuations of the electric current inside an electrical conductor, which happens without any applied voltage, due to the random thermal motion of the charge carriers (the electrons). ...


There will be also Flicker noise due to electrons transit, but depending on 1/f, will be much lower than thermal noise wether the frequency is high. Hence, in pulse radar, the system will be always heterodyne. See intermediate frequency. 1/f noise is a signal or process with a frequency spectrum such that the spectral energy density is proportional to the reciprocal of the frequency. ... In telecommunications, to heterodyne is to generate new frequencies by mixing two or more signals in a nonlinear device such as a vacuum tube, transistor, or diode mixer. ... An intermediate frequency (IF) is a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. ...


Clutter

Clutter refers to actual radio frequency (RF) echoes returned from targets which are by definition uninteresting to the radar operators in general. Such targets mostly include natural objects such as ground, sea, precipitation (such as rain, snow or hail), sand storms, animals (especially birds), atmospheric turbulence, and other atmospheric effects (such as ionosphere reflections and meteor trails). Clutter may also be returned from man-made objects such as buildings and, intentionally, by radar countermeasures such as chaff. Sandstorm can refer to: Sandstorms, a term used for dust storms in the desert. ... In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic, stochastic property changes. ... Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ... Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ... Modern US Navy RR-129 and RR-124 chaff countermeasures and containers Chaff, originally called Window by the British, and Düppel by the WWII era German Luftwaffe, is a radar countermeasure in which aircraft or other targets spread a cloud of small, thin pieces of aluminium, metallised glass fibre...


Some clutter may also be caused by a long radars waveguide between the radar transceiver and the antenna. In a typical plan position indicator (PPI) radar with a rotating antenna, this will usually be seen as a "sun" or "sunburst" in the centre of the display as the receiver responds to echoes from dust particles and misguided RF in the waveguide. Adjusting the timing between when the transmitter sends a pulse and when the receiver stage is enabled will generally reduce the sunburst without affecting the accuracy of the range, since most sunburst is caused by diffused transmit pulse reflected before it leaves the antenna. Look up waveguide in Wiktionary, the free dictionary. ... An annotated picture of one of the first Plan Position Indicator images - Pembroke and Milford Haven as seen on the PPI of an early H2S screen The Plan Position Indicator, known as PPI, is the most common way to represent radar data. ...


While some clutter sources may be undesirable for some radar applications (such as storm clouds for air-defence radars), they may be desirable for others (meteorological radars in this example). Clutter is considered a passive interference source, since it only appears in response to radar signals sent by the radar. Meteorology is the scientific study of the atmosphere that focuses on weather processes and forecasting. ...


There are several methods of detecting and neutralizing clutter. Many of these methods rely on the fact that clutter tends to appear static between radar scans. Therefore, when comparing subsequent scans echoes, desirable targets will appear to move and all stationary echoes can be eliminated. Sea clutter can be reduced by using horizontal polarization, while rain is reduced with circular polarization (note that meteorological radars wish for the opposite effect, therefore using linear polarization the better to detect precipitation). Other methods attempt to increase the signal-to-clutter ratio. In electrodynamics, circular polarization of electromagnetic radiation is a polarization such that the tip of the electric field vector, at a fixed point in space, describes a circle as time progresses. ... In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation. ...


CFAR (Constant False-Alarm Rate, a form of Automatic Gain Control, or AGC) is a method relying on the fact that clutter returns far outnumber echoes from targets of interest. The receiver's gain is automatically adjusted to maintain a constant level of overall visible clutter. While this does not help detect targets masked by stronger surrounding clutter, it does help to distinguish strong target sources. In the past, radar AGC was electronically controlled and affected the gain of the entire radar receiver. As radars evolved, AGC became computer-software controlled, and affected the gain with greater granularity, in specific detection cells. Constant false alarm rate (CFAR) detection refers to a common form of adaptive algorithm used in radar systems to detect target returns against a background of noise, clutter and interference. ... Automatic gain control (AGC) is an electronic system found in many types of devices. ...

Radar multipath echoes from an actual target cause ghosts to appear.
Radar multipath echoes from an actual target cause ghosts to appear.

Clutter may also originate from multipath echoes from valid targets due to ground reflection, atmospheric ducting or ionospheric reflection/refraction. This specific clutter type is especially bothersome, since it appears to move and behave like other normal (point) targets of interest, thereby creating a ghost. In a typical scenario, an aircraft echo is multipath-reflected from the ground below, appearing to the receiver as an identical target below the correct one. The radar may try to unify the targets, reporting the target at an incorrect height, or - worse - eliminating it on the basis of jitter or a physical impossibility. These problems can be overcome by incorporating a ground map of the radar's surroundings and eliminating all echoes which appear to originate below ground or above a certain height. In newer ATC radar equipment algorithms are used to identify the false targets by comparing the current pulse returns, to those adjacent, as well as calculating return improbabilities due to calculated height, distance, and radar timing. Image File history File links Multichemin. ... Image File history File links Multichemin. ... PRIMERGY MultiPath PRIMERGY MultiPath supports redundant Fiber Channel paths, the configured connections between server and subsystem that are such an important component of disaster-tolerant servers and clusters. ... Look up echo in Wiktionary, the free dictionary. ... An artists interpretation of a ghostly woman on a flight of stairs, based on common descriptions A ghost is usually defined as the apparition of a deceased person, frequently similar in appearance to that person, and encountered in places she or he frequented, or in association with the person... PRIMERGY MultiPath PRIMERGY MultiPath supports redundant Fiber Channel paths, the configured connections between server and subsystem that are such an important component of disaster-tolerant servers and clusters. ... Atmospheric ducting, in communications and radar, is a type of anomalous radio wave propagation, similar to a mirage in light propagation. ... Ionospheric reflection: Of electromagnetic waves propagating in the ionosphere, a redirection, bending--by a complex process involving reflection and refraction--of the waves back toward the Earth. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... In telecommunication, jitter is an abrupt and unwanted variation of one or more signal characteristics, such as the interval between successive pulses, the amplitude of successive cycles, or the frequency or phase of successive cycles. ...


Jamming

Radar jamming refers to RF signals originating from sources outside the radar, transmitting in the radar's frequency and thereby masking targets of interest. Jamming may be intentional, as with an anti-radar electronic warfare (EW) tactic, or unintentional, as with friendly forces operating equipment that transmits using the same frequency range. Jamming is considered an active interference source, since it is initiated by elements outside the radar and in general unrelated to the radar signals. Radar jamming is the intentional emission of radio frequency signals to interfere with the operation of a radar by saturating its receiver with false information. ... // Electronic warfare (EW) is the use of the electromagnetic spectrum to effectively deny the use of this phenomena by an adversary, while optimizing its use by friendly forces. ...


Jamming is problematic to radar since the jamming signal only needs to travel one-way (from the jammer to the radar receiver) whereas the radar echoes travel two-ways (radar-target-radar) and are therefore significantly reduced in power by the time they return to the radar receiver. Jammers therefore can be much less powerful than their jammed radars and still effectively mask targets along the line of sight from the jammer to the radar (Mainlobe Jamming). Jammers have an added effect of affecting radars along other line-of-sights, due to the radar receiver's sidelobes (Sidelobe Jamming). When viewing a scene, as in optics, photography, or even hunting, the line of sight is the straight line between the observer and the target. ... In antenna engineering, the parts of the radiation pattern that are not the main lobe. ...


Mainlobe jamming can generally only be reduced by narrowing the mainlobe solid angle, and can never fully be eliminated when directly facing a jammer which uses the same frequency and polarization as the radar. Sidelobe jamming can be overcome by reducing receiving sidelobes in the radar antenna design and by using an omnidirectional antenna to detect and disregard non-mainlobe signals. Other anti-jamming techniques are frequency hopping and polarization. See Electronic counter-counter-measures for details. A solid angle is the three dimensional analog of the ordinary angle. ... An omnidirectional antenna is an antenna system which radiates power uniformly in one plane with a directive pattern shape in a perpendicular plane. ... Frequency-hopping spread spectrum (FHSS) is a spread-spectrum method of transmitting signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... Electronic counter-counter measures, or ECCM, refers to an electronic systems ability to function in the presence of Electronic_counter-measures, or ECM. Because the label ECCM is fairly cumbersome, the synonym, electronic protection, or Electronic Protective Measures, or EPM, is more common in modern usage. ...


Interference has recently become a problem for C-band (5.66 GHz) meteorological radars with the proliferation of 5.4 GHz band WiFi equipment.[8] C band (compromise band) is a portion of electromagnetic spectrum in the microwave range of frequencies ranging from 4 to 6 GHz. ... A gigahertz is a billion hertz or a thousand megahertz, a measure of frequency. ... Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for Wireless Fidelity, is a set of standards for wireless local area networks (WLAN) currently based on the IEEE 802. ...


Radar signal processing

Distance measurement

Transit time

Pulse radar

One way to measure the distance to an object is to transmit a short pulse of radio signal (electromagnetic radiation), and measure the time it takes for the reflection to return. The distance is one-half the product of round trip time (because the signal has to travel to the target and then back to the receiver) and the speed of the signal. Since radio waves travel at the speed of light (186,000 miles per second or 300,000,000 meters per second), accurate distance measurement requires high-performance electronics. Image File history File links Radarops. ... Image File history File links Radarops. ... Image File history File links Sonar_Principle_EN.svg Beschreibung Description: Principle of a sonar or radar distance measurement Source: Self drawn with Inkscape Date: created 3. ... Image File history File links Sonar_Principle_EN.svg Beschreibung Description: Principle of a sonar or radar distance measurement Source: Self drawn with Inkscape Date: created 3. ...


In most cases, the receiver does not detect the return while the signal is being transmitted. Through the use of a device called a duplexer, the radar switches between transmitting and receiving at a predetermined rate. The minimum range is calculated by measuring the length of the pulse multiplied by the speed of light, divided by two. In order to detect closer targets one must use a shorter pulse length.


A similar effect imposes a maximum range as well. If the return from the target comes in when the next pulse is being sent out, once again the receiver cannot tell the difference. In order to maximize range, one wants to use longer times between pulses, or commonly referred to as a pulse repetition time (PRT).


These two effects tend to be at odds with each other, and it is not easy to combine both good short range and good long range in a single radar. This is because the short pulses needed for a good minimum range broadcast have less total energy, making the returns much smaller and the target harder to detect. This could be offset by using more pulses, but this would shorten the maximum range again. So each radar uses a particular type of signal. Long range radars tend to use long pulses with long delays between them, and short range radars use smaller pulses with less time between them. This pattern of pulses and pauses is known as the pulse repetition frequency (or PRF), and is one of the main ways to characterize a radar. As electronics have improved many radars now can change their PRF thereby changing their range. The newest radars actually fire 2 pulses during one cell. One for short range (~6 miles) and a separate signal for longer ranges (~60 miles). A Radar System uses a Radio Frequency electromagnetic signal reflected from a target to determine information about that target. ...


The distance resolution and the characteristics of the received signal as compared to noise depends heavily on the shape of the pulse. The pulse is often modulated to achieve better performance thanks to a technique known as pulse compression. The word resolution has several meanings, depending on context. ... In telecommunications, modulation is the process of varying a periodic waveform, i. ... Pulse Compression Pulse compression or chirp radar, also known as pulse coding, is a signal processing technique designed to maximise the sensitivity and resolution of radar systems. ...


Frequency modulation

Another form of distance measuring radar is based on frequency modulation. Frequency comparison between two signals is considerably more accurate, even with older electronics, than timing the signal. By changing the frequency of the returned signal and comparing that with the original, the difference can be easily measured. In telecommunications, frequency modulation (FM) conveys information over a carrier wave by varying its frequency. ...


This technique can be used in continuous wave radar, and is often found in aircraft radar altimeters. In these systems a "carrier" radar signal is frequency modulated in a predictable way, typically varying up and down with a sine wave or sawtooth pattern at audio frequencies. The signal is then sent out from one antenna and received on another, typically located on the bottom of the aircraft, and the signal can be continuously compared. Continuous-wave radar system is a radar system where a continuous wave is transmitted by one antenna and a second receives the radio energy reflected from an object. ... A Radar Altimeter measures altitude above the terrain presently beneath the aircraft. ... In trigonometry, an ideal sine wave is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C, where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C...


Since the signal frequency is changing, by the time the signal returns to the aircraft the broadcast has shifted to some other frequency. The amount of that shift is greater over longer times, so greater frequency differences mean a longer distance, the exact amount being the "ramp speed" selected by the electronics. The amount of shift is therefore directly related to the distance traveled, and can be displayed on an instrument. This signal processing is similar to that used in speed detecting Doppler radar. Example systems using this approach are AZUSA, MISTRAM, and UDOP. A source of waves moving to the left. ... AZUSA refers to a ground-based radar tracking system installed at Cape Canaveral, Florida and the NASA Kennedy Space Center. ... MISTRAM (MISsile TRAjectory Measurement) is a high-resolution tracking system used by the United States Air Force (and later NASA) to provide highly detailed trajectory analysis of rocket launches. ... The UDOP (UHF Doppler) multistatic radar and multiradar system (MSRS) utilizes Doppler radar for missile tracking and trajectory measurement. ...


Speed measurement

Speed is the change in distance to an object with respect to time. Thus the existing system for measuring distance, combined with a memory capacity to see where the target last was, is enough to measure speed. At one time the memory consisted of a user making grease-pencil marks on the radar screen, and then calculating the speed using a slide rule. Modern radar systems perform the equivalent operation faster and more accurately using computers. This article does not cite any references or sources. ... Distance is a numerical description of how far apart objects are at any given moment in time. ... In psychology, memory is an organisms ability to store, retain, and subsequently retrieve information. ... Crayola crayons, 24 pack, 2005. ... A typical 10 inch student slide rule (Pickett N902-T simplex trig). ...


However, if the transmitter's output is coherent (phase synchronized), there is another effect that can be used to make almost instant speed measurements (no memory is required), known as the Doppler effect. Most modern radar systems use this principle in the pulse-doppler radar system. Return signals from targets are shifted away from this base frequency via the Doppler effect enabling the calculation of the speed of the object relative to the radar. The Doppler effect is only able to determine the relative speed of the target along the line of sight from the radar to the target. Any component of target velocity perpendicular to this line of sight cannot be determined by Doppler alone tracking the target's azimuth over time must be used. Additional information of the nature of the Doppler returns may be found in the radar signal characteristics article. A source of waves moving to the left. ... Pulse-Doppler is a radar system capable of not only detecting target location (bearing, range, and altitude), but also measuring its radial velocity (range-rate). ... Azimuth is the horizontal component of a direction (compass direction), measured around the horizon, from the north toward the east (i. ... A Radar System uses a Radio Frequency electromagnetic signal reflected from a target to determine information about that target. ...


It is also possible to make a radar without any pulsing, known as a continuous-wave radar (CW radar), by sending out a very pure signal of a known frequency. CW radar is ideal for determining the radial component of a target's velocity, but it cannot determine the target's range. CW radar is typically used by traffic enforcement to measure vehicle speed quickly and accurately where range is not important. Continuous-wave radar system is a radar system where a continuous-wave is transmitted by one antenna and a second receives the radio energy reflected from an object. ...


Reduction of interference effects

Signal processing is employed in radar systems to reduce the interference effects. Signal processing techniques include moving target indication (MTI), pulse doppler, moving target detection (MTD) processors, correlation with secondary surveillance radar (SSR) targets and space-time adaptive processing (STAP). Constant false alarm rate (CFAR) and digital terrain model (DTM) processing are also used in clutter environments. Signal processing is the processing, amplification and interpretation of signals, and deals with the analysis and manipulation of signals. ... Pulse-Doppler is a radar system capable of not only detecting target location (bearing, range, and altitude), but also measuring its radial velocity (range-rate). ... A Secondary Surveillance Radar (SSR) is a radar device installed in air traffic control facilities to allow the precise identification of aircraft. ... Space-time Adaptive Processing (STAP) is a signal processing technique most commonly used in radar systems. ... Constant false alarm rate (CFAR) detection refers to a common form of adaptive algorithm used in radar systems to detect target returns against a background of noise, clutter and interference. ... It has been suggested that Digital elevation model be merged into this article or section. ...


Radar engineering

Radar components
Radar components

A radar has different components: Image File history File links Radar_composantes. ... Image File history File links Radar_composantes. ...

  • A transmitter that generates the radio signal with an oscillator such as a klystron or a magnetron and controls its duration by a modulator.
  • A waveguide that links the transmitter and the antenna.
  • A duplexer that serves as a switch between the antenna and the transmitter or the receiver for the signal when the antenna is used in both situations.
  • A receiver. Knowing the shape of the desired received signal (a pulse), an optimal receiver can be designed using a matched filter.
  • An electronic section that controls all those devices and the antenna to perform the radar scan ordered by a software.
  • A link to end users.

Antenna tower of Crystal Palace transmitter, London A transmitter (sometimes abbreviated XMTR) is an electronic device which with the aid of an antenna propagates an electromagnetic signal such as radio, television, or other telecommunications. ... For the musical use of modulation, see modulation (music). ... Look up waveguide in Wiktionary, the free dictionary. ... 1) A duplexer is a device that combines two or more signals onto a common channel or medium to increase its transmission efficiency. ... In radio terminology, a receiver is an electronic circuit that receives a radio signal from an antenna and decodes the signal for use as sound, pictures, navigational-position information, etc. ... A matched filter is obtained by correlating a known signal, or template, with an unknown signal to detect the presence of the template in the unknown signal. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ...

Antenna design

Radio signals broadcast from a single antenna will spread out in all directions, and likewise a single antenna will receive signals equally from all directions. This leaves the radar with the problem of deciding where the target object is located.


Early systems tended to use omni-directional broadcast antennas, with directional receiver antennas which were pointed in various directions. For instance the first system to be deployed, Chain Home, used two straight antennas at right angles for reception, each on a different display. The maximum return would be detected with an antenna at right angles to the target, and a minimum with the antenna pointed directly at it (end on). The operator could determine the direction to a target by rotating the antenna so one display showed a maximum while the other shows a minimum. An omnidirectional antenna is an antenna system which radiates power uniformly in one plane with a directive pattern shape in a perpendicular plane. ... Marconi tower at sunset. ... This article is about angles in geometry. ... A sphere rotating around its axis. ...


One serious limitation with this type of solution is that the broadcast is sent out in all directions, so the amount of energy in the direction being examined is a small part of that transmitted. To get a reasonable amount of power on the "target", the transmitting aerial should also be directional. This diagram shows how the law works. ...


Parabolic reflector

More modern systems use a steerable parabolic "dish" to create a tight broadcast beam, typically using the same dish as the receiver. Such systems often combine two radar frequencies in the same antenna in order to allow automatic steering, or radar lock. A parabola A graph showing the reflective property, the directrix (light blue), and the lines connecting the focus and directrix to the parabola (blue) In mathematics, the parabola (from the Greek: παραβολή) (IPA pronunciation: ) is a conic section generated by the intersection of a right circular conical surface and a plane...


Types of scan

  1. Primary Scan: A scanning technique where the main antenna aerial is moved to produce a scanning beam, examples include circular scan, sector scan etc
  2. Secondary Scan: A scanning technique where the antenna feed is moved to produce a scanning beam, example include conical scan, unidirectional sector scan, loge switching etc.
  3. Palmer Scan: A scanning technique that produces a scanning beam by moving the main antenna and its feed. A Palmer Scan is a combination of a Primary Scan and a Secondary Scan.
Phased array: Not all radar antennas must rotate to scan the sky.
Phased array: Not all radar antennas must rotate to scan the sky.

Image File history File links PAVE_PAWS_Radar_Clear_AFS_Alaska. ... Image File history File links PAVE_PAWS_Radar_Clear_AFS_Alaska. ... For the ultrasonic and medical imaging application, see phased array ultrasonics. ...

Slotted waveguide

Main article: Slotted waveguide

Applied similarly to the parabolic reflector the slotted waveguide is moved mechanically to scan and is particularly suitable for non-tracking surface scan systems, where the vertical pattern may remain constant. Owing to lower cost and less wind exposure, shipboard, airport surface, and harbour surveillance radars now use this in preference to the parabolic antenna. A slotted waveguide is a waveguide that is used as an antenna in microwave radar applications. ...


Phased array

Main article: Phased array

Another method of steering is used in a phased array radar. This uses an array of similar aerials suitably spaced, the phase of the signal to each individual aerial being controlled so that the signal is reinforced in the desired direction and cancels in other directions. If the individual aerials are in one plane and the signal is fed to each aerial in phase with all others then the signal will reinforce in a direction perpendicular to that plane. By altering the relative phase of the signal fed to each aerial the direction of the beam can be moved because the direction of constructive interference will move. Because phased array radars require no physical movement the beam can scan at thousands of degrees per second, fast enough to irradiate and track many individual targets, and still run a wide-ranging search periodically. By simply turning some of the antennas on or off, the beam can be spread for searching, narrowed for tracking, or even split into two or more virtual radars. However, the beam cannot be effectively steered at small angles to the plane of the array, so for full coverage multiple arrays are required, typically disposed on the faces of a triangular pyramid (see picture). For the ultrasonic and medical imaging application, see phased array ultrasonics. ... This article does not cite any references or sources. ... This article or section is in need of attention from an expert on the subject. ...


Phased array radars have been in use since the earliest years of radar use in World War II, but limitations of the electronics led to fairly poor accuracy. Phased array radars were originally used for missile defense. They are the heart of the ship-borne Aegis combat system, and the Patriot Missile System, and are increasingly used in other areas because the lack of moving parts makes them more reliable, and sometimes permits a much larger effective antenna, useful in fighter aircraft applications that offer only confined space for mechanical scanning. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... It has been suggested that Guided missile be merged into this article or section. ... In military science, defense (or defence) is the art of preventing an enemy from conquering territory. ... USS Lake Champlain, a Ticonderoga-class Aegis guided missile cruiser, launched in 1987 The Aegis combat system is an integrated missile guidance system used by the United States Navy. ... Four Patriot missiles like the one shown here can be fired from this mobile launcher between loadings. ...


As the price of electronics has fallen, phased array radars have become more and more common. Almost all modern military radar systems are based on phased arrays, where the small additional cost is far offset by the improved reliability of a system with no moving parts. Traditional moving-antenna designs are still widely used in roles where cost is a significant factor such as air traffic surveillance, weather radars and similar systems.


Phased array radars are also valued for use in aircraft, since they can track multiple targets. The first aircraft to use a phased array radar is the B-1B Lancer. The first aircraft fighter to use phased array radar was the Mikoyan MiG-31. The MiG-31M's SBI-16 Zaslon phased array radar is considered to be the world's most powerful fighter radar [3]. This article does not cite any references or sources. ... Mikoyan MiG-31 Foxhound The Mikoyan MiG-31 (МиГ-31 in Cyrillic script) (NATO reporting name Foxhound) is a high-speed interceptor developed to replace the MiG-25. ...


Phased-array interferometry "aperture synthesis" techniques, using an array of separate dishes that are phased into a single effective aperture, are not typically used for radar applications, although they are widely used in radio astronomy. Because of the Thinned array curse, such arrays of multiple apertures, when used in transmitters, result in narrow beams at the expense of reducing the total power transmitted to the target. In principle, such techniques used could increase the spatial resolution, but the lower power means that this is generally not effective. Aperture synthesis by post-processing of motion data from a single moving source, on the other hand, is widely used in space and airborne radar systems (see "Synthetic aperture radar"). It has been suggested that Optical interferometry be merged into this article or section. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... The thinned array curse (sometimes, sparse array curse) is a theorem in electromagnetic theory of transmitters. ... The surface of Venus, as imaged by the Magellan probe using SAR Synthetic aperture radar (SAR) is a form of radar in which sophisticated post-processing of radar data is used to produce a very narrow effective beam. ...


Frequency bands

The traditional band names originated as code-names during World War II and are still in military and aviation use throughout the world in the 21st century. They have been adopted in the United States by the IEEE, and internationally by the ITU. Most countries have additional regulations to control which parts of each band are available for civilian or military use. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... The International Telecommunication Union (ITU; French: Union internationale des télécommunications, Spanish: Unión Internacional de Telecomunicaciones) is an international organization established to standardize and regulate international radio and telecommunications. ...


Other users of the radio spectrum, such as the broadcasting and electronic countermeasures (ECM) industries, have replaced the traditional military designations with their own systems. Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. ... Inspecting an F-16 electronic countermeasures pod Electronic countermeasures or ECM are any sort of electrical or electronic device designed entirely to spoof radar, sonar, or other detection systems. ...

Radar frequency bands
Band Name Frequency Range Wavelength Range Notes
HF 3–30 MHz 10–100 m coastal radar systems, over-the-horizon radar (OTH) radars; 'high frequency'
P < 300 MHz 1 m+ 'P' for 'previous', applied retrospectively to early radar systems
VHF 50–330 MHz 0.9-6 m very long range, ground penetrating; 'very high frequency'
UHF 300–1000 MHz 0.3-1 m very long range (e.g. ballistic missile early warning), ground penetrating, foliage penetrating; 'ultra high frequency'
L 1–2 GHz 15–30 cm long range air traffic control and surveillance; 'L' for 'long'
S 2–4 GHz 7.5–15 cm terminal air traffic control, long range weather, marine radar; 'S' for 'short'
C 4–8 GHz 3.75-7.5 cm Satellite transponders; a compromise (hence 'C') between X and S bands; weather
X 8–12 GHz 2.5-3.75 cm missile guidance, marine radar, weather, medium-resolution mapping and ground surveillance; in the USA the narrow range 10.525 GHz ±25 MHz is used for airport radar. Named X band because the frequency was a secret during WW2.
Ku 12–18 GHz 1.67-2.5 cm high-resolution mapping, satellite altimetry; frequency just under K band (hence 'u')
K 18–27 GHz 1.11-1.67 cm from German kurz, meaning 'short'; limited use due to absorption by water vapour, so Ku and Ka were used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band radar guns operate at 24.150 ± 0.100 GHz.
Ka 27–40 GHz 0.75-1.11 cm mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to trigger cameras which take pictures of license plates of cars running red lights, operates at 34.300 ± 0.100 GHz.
mm 40–300 GHz 7.5 mm - 1 mm millimetre band, subdivided as below. The letter designators appear to be random, and the frequency ranges dependent on waveguide size. Multiple letters are assigned to these bands by different groups. These are from Baytron, a now defunct company that made test equipment.
Q 40–60 GHz 7.5 mm - 5 mm Used for Military communication.
V 50–75 GHz 6.0–4 mm Very strongly absorbed by the atmosphere.
E 60–90 GHz 6.0–3.33 mm
W 75–110 GHz 2.7 - 4.0 mm used as a visual sensor for experimental autonomous vehicles, high-resolution meteorological observation, and imaging.

HF, Hf or hf can refer to: Hafnium, a chemical element Hydrogen fluoride, a diatomic compound which can dissolve in water to form hydrofluoric acid Hydrofluoric acid, a highly corrosive solution of hydrogen fluoride in water High frequency, the range of radio frequencies from 3 MHz to 30 MHz Higher... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... ‹ The template below (Unit of length) is being considered for deletion. ... Over-The-Horizon radar (OTHR) is a design concept for radar system to overcome the problem that radio waves (a form of light) travel in a straight line, making over the horizon detection difficult. ... Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. ... Ultra high frequency (UHF) designates a range (band) of electromagnetic waves whose frequency is between 300 MHz and 3. ... Phased array BMEWS Installation at Thule, Greenland The Ballistic Missile Early Warning System (BMEWS) was the first operational ballistic missile detection radar. ... L band (20-cm radar long-band) is a portion of the microwave band of the electromagnetic spectrum ranging roughly from 0. ... A gigahertz is a billion hertz or a thousand megahertz, a measure of frequency. ... A centimetre (American spelling centimeter, symbol cm) is a unit of length that is equal to one hundredth of a metre, the current SI base unit of length. ... For the Canadian musical group, see Air Traffic Control (band). ... This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... The S band ranges from 2 to 4 GHz. ... C band (compromise band) is a portion of electromagnetic spectrum in the microwave range of frequencies ranging from 4 to 6 GHz. ... The X band (3-cm radar spot-band) of the microwave band of the electromagnetic spectrum roughly ranges from 5. ... It has been suggested that Guided missile be merged into this article or section. ... The Ku band (kay-yoo kurz-under band) is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 11 to 18 GHz. ... K band is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging between 12 to 63 GHz. ... It has been suggested that multiple sections of steam be merged into this article or section. ... The Ka band (kurz-above band) is a portion of the K band of the microwave band of the electromagnetic spectrum. ... Extremely high frequency is the highest radio frequency band. ... The V band (vee-band) of the electromagnetic spectrum ranges from 50 to 75 GHz. ... The W band of the microwave part of the electromagnetic spectrum and ranges from 75 to 111 GHz. ...

Radar modulators

Modulators are sometimes called pulsers and act to provide the short pulses of power to the magnetron. This technology is known as Pulsed power. In this way, the transmitted pulse of RF radiation is kept to a defined, and usually very short, duration. Modulators consist of a high voltage pulse generator formed from a HV supply, a pulse forming network or line (PFN) and a high voltage switch such as a thyratron. In telecommunications, modulation is the process of varying a periodic waveform, i. ... A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... Pulsed power is the science and technology of accumulating energy over a relatively long period of time and releasing it very quickly. ... A Pulse forming network (PFN) converts direct current or alternating current to continous directional square pulses at high energy levels of high frequency. ... A thyratron is a type of gas filled tube used as a high energy electrical switch. ...


A klystron tube is an amplifier, so it can be modulated by its low power input signal. A klystron is a specialized vacuum tube (evacuated electron tube) called a linear-beam tube. ...


Radar coolant

Coolanol and PAO (poly-alpha olefin) are the two main coolants used to cool airborne radar equipment today.[citation needed] Coolanol is a trade name for a series of silicate ester industrial coolants. ... A polyolefin is a polymer produced from a simple olefin, or alkene as a monomer. ...


The U.S. Navy has instituted a program named Pollution Prevention (P2) to reduce or eliminate the volume and toxicity of waste, air emissions, and effluent discharges. Because of this Coolanol is used less often today. The United States Navy (USN) is the branch of the United States armed forces responsible for naval operations. ... Pollution prevention (P2) is a term used to describe a series of techniques that are used to reduce the amount of pollution generated. ...


PAO is a synthetic lubricant composition is a blend of a polyol ester admixed with effective amounts of an antioxidant, yellow metal pacifier and rust inhibitors. The polyol ester blend includes a major proportion of poly(neopentyl polyol) ester blend formed by reacting poly(pentaerythritol) partial esters with at least one C7 to C12 carboxylic acid mixed with an ester formed by reacting a polyol having at least two hydroxyl groups and at least one C8-C10 carboxylic acid. Preferably, the acids are linear and avoid those which can cause odours during use. Effective additives include secondary arylamine antioxidants, triazole derivative yellow metal pacifier and an amino acid derivative and substituted primary and secondary amine and/or diamine rust inhibitor. A carboxylic acid ester. ... Space-filling model of the antioxidant metabolite glutathione. ... Pentaerythritol is a polyol used in the fabrication of PETN and varnishes. ... Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted... Triazole refers to either one of a pair of isomeric chemical compounds with molecular formula C2H3N3, having a five-membered ring of two carbon atoms and three nitrogen atoms. ... Phenylalanine is one of the standard amino acids. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ...


A synthetic coolant/lubricant composition, comprising an ester mixture of 50 to 80 weight percent of poly(neopentyl polyol) ester formed by reacting a poly(neopentyl polyol) partial ester and at least one linear monocarboxylic acid having from 6 to 12 carbon atoms, and 20 to 50 weight percent of a polyol ester formed by reacting a polyol having 5 to 8 carbon atoms and at least two hydroxyl groups with at least one linear monocarboxylic acid having from 7 to 12 carbon atoms, the weight percents based on the total weight of the composition.


Radar functions and roles

Surface search radar display commonly found on ships
Surface search radar display commonly found on ships

Image File history File linksMetadata Download high-resolution version (2048x1536, 1408 KB) Description écran radar marine Licensing Source Clipper File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Radar Metadata This file contains additional information, probably added from the... Image File history File linksMetadata Download high-resolution version (2048x1536, 1408 KB) Description écran radar marine Licensing Source Clipper File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Radar Metadata This file contains additional information, probably added from the...

Detection and search radars

An early warning radar is any radar system used primarily for the long-range detection of its selected targets. ... Ground-controlled interception (GCI) is a technique whereby one or more radar stations are linked to a command center with communications equipment in order to launch and/or guide aircraft to intercept incoming airborne threats. ... United States Air Force E-3 Sentry An Airborne Early Warning (AEW) system is a radar system carried by an aircraft which is designed to detect other aircraft. ... Over-The-Horizon radar (OTHR) is a design concept for radar system to overcome the problem that radio waves (a form of light) travel in a straight line, making over the horizon detection difficult. ... Akash Missile Firing French Air Force Crotale battery Bendix Rim-8 Talos surface to air missile of the US Navy A surface-to-air missile (SAM) is a missile designed to be launched from the ground to destroy aircraft. ... “Flak” redirects here. ... “A/S” redirects here. ... Mill Valley AFS height finder radar (1973) A height finder is a ground based aircraft altitude measuring device. ...

Threat radars

“Flak” redirects here. ... Akash Missile Firing French Air Force Crotale battery Bendix Rim-8 Talos surface to air missile of the US Navy A surface-to-air missile (SAM) is a missile designed to be launched from the ground to destroy aircraft. ... Precision Approach Radar (PAR) is a type of radar guidance system designed to provide lateral and vertical guidance to a pilot. ... A fire-control system is a computer, often mechanical, which is designed to assist a weapon system in hitting its target. ... A guided bomb strikes an underground facility Missile guidance technologies of missile systems use a variety of methods to guide a missile to its intended target. ...

Missile guidance systems

A US Navy VF-103 Jolly Rogers F-14 Tomcat fighter launches an AIM-54 Phoenix long-range air-to-air missile. ... An air-to-surface missile (also, air-to-ground missile, ASM or AGM) is a missile designed to be launched from military aircraft (bombers, attack aircraft, fighter aircraft or other kinds) and strike ground targets on land, at sea, or both. ... Akash Missile Firing French Air Force Crotale battery Bendix Rim-8 Talos surface to air missile of the US Navy A surface-to-air missile (SAM) is a missile designed to be launched from the ground to destroy aircraft. ... A surface-to-surface missile (SSM) is a guided projectile launched from a hand-held, vehicle mounted, trailer mounted or fixed installation or from a ship. ...

Battlefield and reconnaissance radar

Military map marking symbol Radar as of NATO standard APP-6a
Military map marking symbol Radar as of NATO standard APP-6a

Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... APP-6A is the NATO standard for military map marking symbols. ... The surface of Venus, as imaged by the Magellan probe using SAR Synthetic aperture radar (SAR) is a form of radar in which sophisticated post-processing of radar data is used to produce a very narrow effective beam. ... Perimeter Surveillance Radar (PSR) is a class of radar sensors that monitor activity surrounding or on critical infrastructure areas such as airports, seaports, military installations, national borders, refineries and other critical industry and the like. ...

Air Traffic Control and navigation

Air traffic control radar at London Heathrow Airport
Air traffic control radar at London Heathrow Airport

Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2560 × 1920 pixel, file size: 1. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2560 × 1920 pixel, file size: 1. ... “Heathrow” redirects here. ... For the Canadian musical group, see Air Traffic Control (band). ... For the Canadian musical group, see Air Traffic Control (band). ... A Secondary Surveillance Radar (SSR) is a radar device installed in air traffic control facilities to allow the precise identification of aircraft. ... Precision Approach Radar (PAR) is a type of radar guidance system designed to provide lateral and vertical guidance to a pilot. ... D-VOR/DME ground station Distance Measuring Equipment (DME) is a transponder-based radio navigation technology that measures distance by timing the propagation delay of VHF or UHF radio signals. ... Telegraph Signal Tower at Cobbs Hill, near New Market, Virginia, 1864. ... A Radar Altimeter measures altitude above the terrain presently beneath the aircraft. ... Terrain-following radar is an aerospace technology that allows a very-low-flying aircraft to automatically maintain a constant altitude. ...

Space and range instrumentation radar systems

  • Space (SP) Tracking Systems
  • Range Instrumentation (RI) Systems
  • Video Relay/Downlink Systems
  • Space-Based Radar

Space-based radar refers to space-borne radar systems that may have any of a variety of purposes. ...

Weather-sensing Radar systems



Radars for biological research

For the Canadian musical group, see Air Traffic Control (band). ... A fire-control system is a computer, often mechanical, which is designed to assist a weapon system in hitting its target. ...

Through The Wall Radar Systems

Radar systems which operate in the UWB (ultra-wide-band)frequencies, can sense a human object behind walls. This is done due to the fact that the reflective characteristics of humans is much greater than any other types of objects and is second only to metals. transmitting a signal towards the wall can cause a very weak signal to penetrate the wall get to the human object refelet from it and penetrate the wall again. different walls inhibit different attenuation and dispersion. Sensing the movement requires a simple to a very sophisticated transceivers: Sensing or 1-D image only is done with a single transceiver a 2-D view requires much more sensors and more elaborate technology Camero-tech is the only 1 company currently which offer 3D image together with 2D and 1D for a mobile through the wall imaging system [9].


Video games

Many video games dedicate a small portion of the screen to a subsidiary display that indicates the position of the player relative to other objects and players. The games sometimes refer to this sub-display as the 'radar', although it is not usually meant to represent a real radar system.


See also

Electronics Portal
Nautical Portal

Image File history File links Nuvola_apps_ksim. ... Image File history File links No higher resolution available. ... A crossed-field amplifier (CFA) is a specialized vacuum tube, frequently used as a microwave amplifier in very-high-power transmitters. ... Amplitude monopulse direction finding refers to a common technique employed in radar systems to improve the accuracy with which the direction of arrival of a pulse can be estimated. ... Bistatic Doppler shift is a specific example of the Doppler effect that is observed by a radar or sonar system with a separated transmitter and receiver. ... Bistatic range refers to the basic measurement of range made by a radar or sonar system with separated transmitter and receiver. ... Constant false alarm rate (CFAR) detection refers to a common form of adaptive algorithm used in radar systems to detect target returns against a background of noise, clutter and interference. ... This article is about the chemical compound. ... A klystron is a specialized vacuum tube (evacuated electron tube) called a linear-beam tube. ... This is a list of radars. ... A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... Over-The-Horizon radar (OTHR) is a design concept for radar system to overcome the problem that radio waves (a form of light) travel in a straight line, making over the horizon detection difficult. ... This article or section does not adequately cite its references or sources. ... LORAN (LOng RAnge Navigation) is a terrestrial navigation system using low frequency radio transmitters that use the time interval between radio signals received from three or more stations to determine the position of a ship or aircraft. ... This article is about underwater sound propagation. ... A traveling wave tube (TWT) is an electronic device used to produce high-power radio frequency signals. ... Radar has many different types and applications: Search radars scan a wide area with pulses of short radio waves. ... 3D Radar provides for radar coverage on three dimensions unlike the more common 2D Radar. ... APAR AESA An Active Electronically Scanned Array (AESA), also known as active phased array radar is a revolutionary type of radar whose transmitter and receiver functions are composed of numerous small transmit/receive (T/R) modules. ... Bistatic radar is the name given to a radar system which comprises a transmitter and receiver which are separated by a distance that is comparable to the expected target distance. ... Continuous-wave radar system is a radar system where a continuous-wave is transmitted by one antenna and a second receives the radio energy reflected from an object. ... Doppler Effect Doppler radar uses the Doppler effect to measure the radial velocity of targets in the antennas directional beam. ... Frequency Modulated Continuous-wave radar (FM-CW) is a radar system where a known stable frequency continuous wave radio energy is modulated by a triangular modulation signal so that it varies gradually and then mixes with the signal reflected from a target object with this transmit signal to produce a... Traditional radar sends directional pulses of electromagnetic energy and detects the presence, position and motion of an object (such as an airplane) by analyzing the portion of the energy reflected from the object back to the radar station. ... Incoherent scatter refers to a ground-based technique for studying the earths ionosphere. ... A low probabililty of intercept radar has the characteristic that it is unlikely to be detected by passive radar detection equipment (such as a radar warning receiver - RWR) while it is searching for or tracking a target. ... The millimeter wave cloud radar (MMCR) is a remote sensing instrument that transmits a radar pulse directly overhead to determine the tops and bottoms of clouds. ... Monopulse radars are an adaptation of conical scanning radars which send additional information in the radar signal in order to avoid problems caused by rapid changes in signal strength. ... Passive radar systems (also referred to a passive coherent location and passive covert radar) encompass a class of radar systems that detect and track objects by processing reflections from non-cooperative sources of illumination in the environment, such as commercial broadcast and communications signals. ... The planar array radar uses a high-gain planar array antenna. ... Precision Approach Radar (PAR) is a type of radar guidance system designed to provide lateral and vertical guidance to a pilot. ... Pulse-doppler is a radar system that functions by sending short pulses of radio energy and simultanously listens for the echo from objects using the same attenna. ... U.S. Army soldier uses a radar gun to catch speeding violators at Tallil Air Base, Iraq. ... The U.S. Army SCR-270 radar, also known as The Pearl Harbor Radar was one of the first radars. ... X band is a radio frequency range designation that denotes the operational frequency of a specific radar system. ... An early H2S picture of the Pembroke and Milford Haven area The H2S radar was used in bombers of RAF Bomber Command. ... Marconi tower at sunset. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

Notes

Kwajalein Atoll - NASA NLT Landsat 7 (Visible Color) Satellite Image Kwajalein Atoll (Marshallese: Kuwajleen) is part of the Republic of the Marshall Islands (RMI). ... Portion of a Pacific atoll showing two islets on the ribbon or barrier reef separated by a deep pass between the ocean and the lagoon. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 83rd day of the year (84th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) will be a leap year starting on Tuesday of the Gregorian calendar. ... is the 247th day of the year (248th in leap years) in the Gregorian calendar. ...

References

Further reading

  • Buderi, Robert, The invention that changed the world: the story of radar from war to peace, Simon & Schuster, 1996. ISBN 0-349-11068-9 ISBN 0-316-90715-4
  • Hall, P.S., T.K. Garland-Collins, R.S. Picton and R.G. Lee, Radar, Brassey's (UK) Ltd., 1991, Land Warfare Series: Vol 9, ISBN 0-08-037711-4.
  • Jones, R.V., Most Secret War, ISBN 1-85326-699-X. R.V. Jones' account of his part in British Scientific Intelligence between 1939 and 1945, working to anticipate the German's radar, radio navigation and V1/V2 developments.
  • Le Chevalier, François, Principles of Radar and Sonar Signal Processing, Artech House, Boston, London, 2002. ISBN 1-58053-338-8.
  • Skolnik, Merrill I., Introduction to Radar Systems, McGraw-Hill (1st ed., 1962; 2nd ed., 1980; 3rd ed., 2001), ISBN 0-07-066572-9. The de-facto radar introduction bible.
  • Skolnik, Merrill I., Radar Handbook. ISBN 0-07-057913-X widely used in the US since the 1970s.
  • Stimson, George W., Introduction to Airborne Radar, SciTech Publishing (2nd edition, 1998), ISBN 1-891121-01-4. Written for the non-specialist. The first half of the book on radar fundamentals is also applicable to ground- and sea-based radar.
  • Bragg, Michael., RDF1 The Location of Aircraft by Radio Methods 1935–1945, Hawkhead Publishing, Paisley 1988 ISBN 0-9531544-0-8 The history of ground radar in the UK during World War II
  • Latham, Colin & Stobbs, Anne., Radar A Wartime Miracle, Sutton Publishing Ltd, Stroud 1996 ISBN 0-7509-1643-5 A history of radar in the UK during World War II told by the men and women who worked on it.
  • Pritchard, David., The Radar War Germany's Pioneering Achievement 1904–1945 Patrick Stephens Ltd, Wellingborough 1989., ISBN 1-85260-246-5
  • Zimmerman, David., Britain's Shield Radar and the Defeat of the Luftwaffe, Sutton Publishing Ltd, Stroud, 2001., ISBN 0-7509-1799-7
  • Brown, Louis., A Radar History of World War II, Institute of Physics Publishing, Bristol, 1999., ISBN 0-7503-0659-9
  • Bowen, E.G., Radar Days, Institute of Physics Publishing, Bristol, 1987., ISBN 0-7503-0586-X
  • Howse, Derek, Radar At Sea The Royal Navy in World War 2, Naval Institute Press, Annapolis, Maryland, USA, 1993, ISBN 1-55750-704-X

Merrill Skolnik (6 Nov, 1927 - ), is a respected researcher in the area of radar systems and the author or editor of a number of standard texts in the field. ... Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from...

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