70-689: AN/SPS-10 is a two-dimensional radar manufactured by Raytheon Technologies . It was used by the US Navy as a surface-search radar after World War II and was equipped aboard naval ships during the Cold War . Variants include AN/SPS-10B , AN-SPS/10E , and AN/SPS-10F . It was first introduced in 1959 during the Fleet Rehabilitation and Modernization, in which it was equipped aboard Gearing -class , Fletcher -class , Allen M. Sumner -class , and Benson -class destroyers. Since then,
140-470: A fractal surface, such as rocks or soil, and are used by navigation radars. A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the refractive index of air, which is called the radar horizon . Even when the beam is emitted parallel to the ground, the beam rises above the ground as the curvature of the Earth sinks below the horizon. Furthermore,
210-431: A root mean square (RMS) voltage (identical to the noise standard deviation ) in volts, dBμV or a mean squared error (MSE) in volts squared. Examples of electrical noise-level measurement units are dBu , dBm0 , dBrn , dBrnC , and dBrn( f 1 − f 2 ), dBrn(144- line ). Noise may also be characterized by its probability distribution and noise spectral density N 0 ( f ) in watts per hertz. A noise signal
280-404: A transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna , a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about
350-424: A transmitter that emits radio waves known as radar signals in predetermined directions. When these signals contact an object they are usually reflected or scattered in many directions, although some of them will be absorbed and penetrate into the target. Radar signals are reflected especially well by materials of considerable electrical conductivity —such as most metals, seawater , and wet ground. This makes
420-451: A certain carrier-to-noise ratio (CNR) at the radio receiver input would result in a certain signal-to-noise ratio in the detected message signal. In a digital communications system, a certain E b / N 0 (normalized signal-to-noise ratio) would result in a certain bit error rate . Telecommunication systems strive to increase the ratio of signal level to noise level in order to effectively transfer data. Noise in telecommunication systems
490-840: A common noun, losing all capitalization . The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy , air-defense systems , anti-missile systems , marine radars to locate landmarks and other ships, aircraft anti-collision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, radar remote sensing , altimetry and flight control systems , guided missile target locating systems, self-driving cars , and ground-penetrating radar for geological observations. Modern high tech radar systems use digital signal processing and machine learning and are capable of extracting useful information from very high noise levels. Other systems which are similar to radar make use of other parts of
560-482: A different dielectric constant or diamagnetic constant from the first, the waves will reflect or scatter from the boundary between the materials. This means that a solid object in air or in a vacuum , or a significant change in atomic density between the object and what is surrounding it, will usually scatter radar (radio) waves from its surface. This is particularly true for electrically conductive materials such as metal and carbon fibre, making radar well-suited to
630-540: A full radar system, that he called a telemobiloscope . It operated on a 50 cm wavelength and the pulsed radar signal was created via a spark-gap. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in Cologne and Rotterdam harbour but was rejected. In 1915, Robert Watson-Watt used radio technology to provide advance warning of thunderstorms to airmen and during
700-749: A physics instructor at the Imperial Russian Navy school in Kronstadt , developed an apparatus using a coherer tube for detecting distant lightning strikes. The next year, he added a spark-gap transmitter . In 1897, while testing this equipment for communicating between two ships in the Baltic Sea , he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation. The German inventor Christian Hülsmeyer
770-498: A proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time. Similarly, in the UK, L. S. Alder took out a secret provisional patent for Naval radar in 1928. W.A.S. Butement and P. E. Pollard developed a breadboard test unit, operating at 50 cm (600 MHz) and using pulsed modulation which gave successful laboratory results. In January 1931,
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#1732793461009840-732: A pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American Robert M. Page , working at the Naval Research Laboratory . The following year, the United States Army successfully tested a primitive surface-to-surface radar to aim coastal battery searchlights at night. This design was followed by a pulsed system demonstrated in May 1935 by Rudolf Kühnhold and
910-442: A rescue. For similar reasons, objects intended to avoid detection will not have inside corners or surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft . These precautions do not totally 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
980-407: A signal in a circuit is unwanted. There are many different noise reduction techniques that can reduce the noise picked up by a circuit. Thermal noise can be reduced by cooling of circuits - this is typically only employed in high accuracy high-value applications such as radio telescopes. The noise level in an electronic system is typically measured as an electrical power N in watts or dBm ,
1050-677: A system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the Daventry Experiment of 26 February 1935, using a powerful BBC shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected, Hugh Dowding , the Air Member for Supply and Research , was very impressed with their system's potential and funds were immediately provided for further operational development. Watson-Watt's team patented
1120-614: A transistor will have more noise than the combined shot noise from its two PN junctions. Flicker noise, also known as 1/ f noise, is a signal or process with a frequency spectrum that falls off steadily into the higher frequencies, with a pink spectrum. It occurs in almost all electronic devices and results from a variety of effects. Burst noise consists of sudden step-like transitions between two or more discrete voltage or current levels, as high as several hundred microvolts , at random and unpredictable times. Each shift in offset voltage or current lasts for several milliseconds to seconds. It
1190-514: A wide region and direct fighter aircraft towards targets. Marine radars are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour, vessel traffic service radar systems are used to monitor and regulate ship movements in busy waters. Meteorologists use radar to monitor precipitation and wind. It has become
1260-907: A writeup on the apparatus was entered in the Inventions Book maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that was used in coastal defence and was incorporated into Chain Home as Chain Home (low) . Before the Second World War , researchers in the United Kingdom, France , Germany , Italy , Japan , the Netherlands , the Soviet Union , and
1330-521: Is a common component of noise in signal processing . In communication systems , noise is an error or undesired random disturbance of a useful information signal in a communication channel . The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from interference , for example in the signal-to-noise ratio (SNR), signal-to-interference ratio (SIR) and signal-to-noise plus interference ratio (SNIR) measures. Noise
1400-469: Is a product of both internal and external sources to the system. Noise is a random process, characterized by stochastic properties such as its variance , distribution , and spectral density . The spectral distribution of noise can vary with frequency , so its power density is measured in watts per hertz (W/Hz). Since the power in a resistive element is proportional to the square of the voltage across it, noise voltage (density) can be described by taking
1470-452: Is a simplification for transmission in a 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 are also considered. Frequency shift is caused by motion that changes the number of wavelengths between the reflector and the radar. This can degrade or enhance radar performance depending upon how it affects
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#17327934610091540-400: Is also known as popcorn noise for the popping or crackling sounds it produces in audio circuits. If the time taken by the electrons to travel from emitter to collector in a transistor becomes comparable to the period of the signal being amplified, that is, at frequencies above VHF and beyond, the transit-time effect takes place and the noise input impedance of the transistor decreases. From
1610-456: Is also typically distinguished from distortion , which is an unwanted systematic alteration of the signal waveform by the communication equipment, for example in signal-to-noise and distortion ratio (SINAD) and total harmonic distortion plus noise (THD+N) measures. While noise is generally unwanted, it can serve a useful purpose in some applications, such as random number generation or dither . Uncorrelated noise sources add according to
1680-451: Is as follows, where F D {\displaystyle F_{D}} is Doppler frequency, F T {\displaystyle F_{T}} is transmit frequency, V R {\displaystyle V_{R}} is radial velocity, and C {\displaystyle C} is the speed of light: Passive radar is applicable to electronic countermeasures and radio astronomy as follows: Only
1750-567: Is intended. Radar relies on its own transmissions rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the target objects themselves, such as infrared radiation (heat). This process of directing artificial radio waves towards objects is called illumination , although radio waves are invisible to the human eye as well as optical cameras. If electromagnetic waves travelling through one material meet another material, having
1820-403: Is often modelled as an additive white Gaussian noise (AWGN) channel. Shot noise in electronic devices results from unavoidable random statistical fluctuations of the electric current when the charge carriers (such as electrons) traverse a gap. If electrons flow across a barrier, then they have discrete arrival times. Those discrete arrivals exhibit shot noise. Typically, the barrier in a diode
1890-417: Is the range. This yields: This shows that the received power declines as the fourth power of the range, which means that the received power from distant targets is relatively very small. Additional filtering and pulse integration modifies the radar equation slightly for pulse-Doppler radar performance , which can be used to increase detection range and reduce transmit power. The equation above with F = 1
1960-433: Is typically considered as a linear addition to a useful information signal. Typical signal quality measures involving noise are signal-to-noise ratio (SNR or S / N ), signal-to-quantization noise ratio (SQNR) in analog-to-digital conversion and compression, peak signal-to-noise ratio (PSNR) in image and video coding and noise figure in cascaded amplifiers. In a carrier-modulated passband analogue communication system,
2030-458: Is unavoidable, and generated by the random thermal motion of charge carriers (usually electrons ), inside an electrical conductor , which happens regardless of any applied voltage . Thermal noise is approximately white , meaning that its power spectral density is nearly equal throughout the frequency spectrum . The amplitude of the signal has very nearly a Gaussian probability density function . A communication system affected by thermal noise
2100-575: Is used. Shot noise is similar to the noise created by rain falling on a tin roof. The flow of rain may be relatively constant, but the individual raindrops arrive discretely. The root-mean-square value of the shot noise current i n is given by the Schottky formula. where I is the DC current, q is the charge of an electron, and Δ B is the bandwidth in hertz. The Schottky formula assumes independent arrivals. Vacuum tubes exhibit shot noise because
2170-628: The Nyquist frequency , since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring: Or when substituting with F D {\displaystyle F_{D}} : As an example, a Doppler weather radar with a pulse rate of 2 kHz and transmit frequency of 1 GHz can reliably measure weather speed up to at most 150 m/s (340 mph), thus cannot reliably determine radial velocity of aircraft moving 1,000 m/s (2,200 mph). In all electromagnetic radiation ,
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2240-717: The RAF's Pathfinder . The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: to locate air, ground and sea targets. This evolved in the civilian field into applications for aircraft, ships, and automobiles. In aviation , aircraft can be equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft
2310-440: The electromagnetic spectrum . One example is lidar , which uses predominantly infrared light from lasers rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents. As early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov ,
2380-407: The reflective surfaces . A corner reflector consists of three flat surfaces meeting like the inside corner of a cube. The structure will reflect waves entering its opening directly back to the source. They are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect. Corner reflectors on boats, for example, make them more detectable to avoid collision or during
2450-534: The "new boy" Arnold Frederic Wilkins to conduct an extensive review of available shortwave units. Wilkins would select a General Post Office model after noting its manual's description of a "fading" effect (the common term for interference at the time) when aircraft flew overhead. By placing a transmitter and receiver on opposite sides of the Potomac River in 1922, U.S. Navy researchers A. Hoyt Taylor and Leo C. Young discovered that ships passing through
2520-413: The 1920s went on to lead the U.K. research establishment to make many advances using radio techniques, including the probing of the ionosphere and the detection of lightning at long distances. Through his lightning experiments, Watson-Watt became an expert on the use of radio direction finding before turning his inquiry to shortwave transmission. Requiring a suitable receiver for such studies, he told
2590-787: The United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, Hungary and Sweden generated its radar technology during the war. In France in 1934, following systematic studies on the split-anode magnetron , the research branch of the Compagnie générale de la télégraphie sans fil (CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on
2660-537: The arrest of Oshchepkov and his subsequent gulag sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar, Gneiss-2 , entered into service in June 1943 on Pe-2 dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944. The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems. Full radar evolved as
2730-479: The beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later, Lawrence A. Hyland at the Naval Research Laboratory (NRL) observed similar fading effects from passing aircraft; this revelation led to a patent application as well as
2800-408: 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 colour so that it cannot be seen by the eye at night. Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of
2870-476: The detection process. As an example, moving target indication can interact with Doppler to produce signal cancellation at certain radial velocities, which degrades performance. Sea-based radar systems, semi-active radar homing , active radar homing , weather radar , military aircraft, and radar astronomy rely on the Doppler effect to enhance performance. This produces information about target velocity during
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2940-411: The detection process. This also allows small objects to be detected in an environment containing much larger nearby slow moving objects. Doppler shift depends upon whether the radar configuration is active or passive. Active radar transmits a signal that is reflected back to the receiver. Passive radar depends upon the object sending a signal to the receiver. The Doppler frequency shift for active radar
3010-626: The device in patent GB593017. Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British Air Ministry , Bawdsey Research Station located in Bawdsey Manor , near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called " Chain Home " along the East and South coasts of England in time for
3080-538: The electric field is perpendicular to the direction of propagation, and the electric field direction is the polarization of the wave. For a transmitted radar signal, the polarization can be controlled to yield different effects. 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
3150-431: The electrons thermalize and move diffusively within the material; the electrons do not have discrete arrival times. Shot noise has been demonstrated in mesoscopic resistors when the size of the resistive element becomes shorter than the electron–phonon scattering length. Where current divides between two (or more) paths, noise occurs as a result of random fluctuations that occur during this division. For this reason,
3220-470: The electrons randomly leave the cathode and arrive at the anode (plate). A tube may not exhibit the full shot noise effect: the presence of a space charge tends to smooth out the arrival times (and thus reduce the randomness of the current). Pentodes and screen-grid tetrodes exhibit more noise than triodes because the cathode current splits randomly between the screen grid and the anode. Conductors and resistors typically do not exhibit shot noise because
3290-473: The entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies. A key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared
3360-466: The firm GEMA [ de ] in Germany and then another in June 1935 by an Air Ministry team led by Robert Watson-Watt in Great Britain. In 1935, Watson-Watt was asked to judge recent reports of a German radio-based death ray and turned the request over to Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such
3430-409: The frequency at which this effect becomes significant, it increases with frequency and quickly dominates other sources of noise. While noise may be generated in the electronic circuit itself, additional noise energy can be coupled into a circuit from the external environment, by inductive coupling or capacitive coupling , or through the antenna of a radio receiver . In many cases noise found on
3500-638: The objects' locations and speeds. Radar was developed secretly for military use by several countries in the period before and during World War II . A key development was the cavity magnetron in the United Kingdom , which allowed the creation of relatively small systems with sub-meter resolution. The term RADAR was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term radar has since entered English and other languages as an anacronym ,
3570-508: The ocean liner Normandie in 1935. During the same period, Soviet military engineer P.K. Oshchepkov , in collaboration with the Leningrad Electrotechnical Institute , produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3 km of a receiver. The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following
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#17327934610093640-531: The outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the Battle of Britain ; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the " Dowding system " for collecting reports of enemy aircraft and coordinating
3710-706: The primary tool for short-term weather forecasting and watching for severe weather such as thunderstorms , tornadoes , winter storms , precipitation types, etc. Geologists use specialized ground-penetrating radars to map the composition of Earth's crust . Police forces use radar guns to monitor vehicle speeds on the roads. Automotive radars are used for adaptive cruise control and emergency breaking on vehicles by ignoring stationary roadside objects that could cause incorrect brake application and instead measuring moving objects to prevent collision with other vehicles. As part of Intelligent Transport Systems , fixed-position stopped vehicle detection (SVD) radars are mounted on
3780-432: The radial component of the velocity is relevant. When the reflector is moving at right angle to the radar beam, it has no relative velocity. Objects moving parallel to the radar beam produce the maximum Doppler frequency shift. When the transmit frequency ( F T {\displaystyle F_{T}} ) is pulsed, using a pulse repeat frequency of F R {\displaystyle F_{R}} ,
3850-414: The response. Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland. Even by standards of the era, CH was crude; instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting
3920-410: The resulting frequency spectrum will contain harmonic frequencies above and below F T {\displaystyle F_{T}} with a distance of F R {\displaystyle F_{R}} . As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of F R {\displaystyle F_{R}} , called
3990-427: The roadside to detect stranded vehicles, obstructions and debris by inverting the automotive radar approach and ignoring moving objects. Smaller radar systems are used to detect human movement . Examples are breathing pattern detection for sleep monitoring and hand and finger gesture detection for computer interaction. Automatic door opening, light activation and intruder sensing are also common. A radar system has
4060-407: 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 power P r returning to the receiving antenna is given by the equation: where In the common case where the transmitter and the receiver are at the same location, R t = R r and the term R t ² R r ² can be replaced by R , where R
4130-701: The signal is attenuated by the medium the beam crosses, and the beam disperses. The maximum range of conventional radar can be limited by a number of factors: Noise (electronics) In electronics , noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics and central to thermodynamics . Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically , and even then quantum noise would remain inherent. Electronic noise
4200-401: The square root of the noise power density, resulting in volts per root hertz ( V / H z {\displaystyle \scriptstyle \mathrm {V} /{\sqrt {\mathrm {Hz} }}} ). Integrated circuit devices, such as operational amplifiers commonly quote equivalent input noise level in these terms (at room temperature). If the noise source is correlated with
4270-482: The sum of their powers. Different types of noise are generated by different devices and different processes. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem ), while other types depend mostly on device type (such as shot noise , which needs a steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise . Johnson–Nyquist noise (more often thermal noise)
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#17327934610094340-491: 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 may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by Rayleigh scattering , an effect that creates Earth's blue sky and red sunsets. When
4410-585: The technology with the U.S. during the 1940 Tizard Mission . In April 1940, Popular Science showed an example of a radar unit using the Watson-Watt patent in an article on air defence. Also, in late 1941 Popular Mechanics had an article in which a U.S. scientist speculated about the British early warning system on the English east coast and came close to what it was and how it worked. Watson-Watt
4480-879: The transmitter. The reflected radar signals captured by the receiving antenna are usually very weak. They can be strengthened by electronic amplifiers . More sophisticated methods of signal processing are also used in order to recover useful radar signals. The weak absorption of radio waves by the medium through which they pass is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as visible light , infrared light , and ultraviolet light , are too strongly attenuated. Weather phenomena, such as fog, clouds, rain, falling snow, and sleet, that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapour, raindrops, or atmospheric gases (especially oxygen) are avoided when designing radars, except when their detection
4550-487: The two length scales are comparable, there may be resonances . Early radars used very long wavelengths that were larger than the targets and thus received a vague signal, whereas many modern systems use shorter wavelengths (a few centimetres or less) that can image objects as small as a loaf of bread. 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
4620-472: The use of radar altimeters possible in certain cases. The radar signals that are reflected back towards the radar receiver are the desirable ones that make radar detection work. If the object is moving either toward or away from the transmitter, there will be a slight change in the frequency of the radio waves due to the Doppler effect . Radar receivers are usually, but not always, in the same location as
4690-608: Was a 1938 Bell Lab unit on some United Air Lines aircraft. Aircraft can land in fog at airports equipped with radar-assisted ground-controlled approach systems in which the plane's position is observed on precision approach radar screens by operators who thereby give radio landing instructions to the pilot, maintaining the aircraft on a defined approach path to the runway. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized military aircraft carry powerful airborne radars to observe air traffic over
4760-621: Was a normal standard for US Navy ships to be equipped with it throughout the Cold War. By 1998, the radar has been put out of service by AN/SPS-55 . Radar Radar is a system that uses radio waves to determine the distance ( ranging ), direction ( azimuth and elevation angles ), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft , ships , spacecraft , guided missiles , motor vehicles , map weather formations , and terrain . A radar system consists of
4830-748: Was sent to the U.S. in 1941 to advise on air defense after Japan's attack on Pearl Harbor . Alfred Lee Loomis organized the secret MIT Radiation Laboratory at Massachusetts Institute of Technology , Cambridge, Massachusetts which developed microwave radar technology in the years 1941–45. Later, in 1943, Page greatly improved radar with the monopulse technique that was used for many years in most radar applications. The war precipitated research to find better resolution, more portability, and more features for radar, including small, lightweight sets to equip night fighters ( aircraft interception radar ) and maritime patrol aircraft ( air-to-surface-vessel radar ), and complementary navigation systems like Oboe used by
4900-463: Was the first to use radio waves to detect "the presence of distant metallic objects". In 1904, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter. He obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also obtained a British patent on 23 September 1904 for
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