Tuesday, June 9, 2009

History of Radar




The history of radar began in the 1900s when engineers invented simple uni-directional ranging devices. The technique developed through the 1920s and 1930s, leading to the introduction of the first early warning radar networks just before the opening of World War II. Progress during the war was rapid; by the end the United States widely deployed radars that fit in a single semi-trailer.
The place of radar in the larger story of science and technology is argued differently by different authors. Radar, far more than the atomic bomb, contributed to Allied victory in World War II.[1] Robert Buderi[2] states that it was also the precursor of much modern technology. From a review of his book[3]:
... radar has been the root of a wide range of achievements since the war, producing a veritable family tree of modern technologies. Because of radar, astronomers can map the contours of far-off planets, physicians can see images of internal organs, meteorologists can measure rain falling in distant places, air travel is hundreds of times safer than travel by road, long-distance telephone calls are cheaper than postage, computers have become ubiquitous and ordinary people can cook their daily dinners in the time between sitcoms, with what used to be called a radar range.
But others think that radar is not so important, since the principles were not new:
Le principe fondamental du radar appartient au patrimoine commun des physiciens : ce qui demeure en fin de compte au crédit réel des techniciens se mesure à la réalisation effective de matériels opérationnels., or roughly
The fundamental principle of the radar belongs to the common patrimony of the physicists : after all, what is left to the real credit of the technicians is measured by the effective realisation of operational materials".


Before the twentieth century

In 1887 the German physicist Heinrich Hertz began experimenting with radio waves in his laboratory. He found that radio waves could be transmitted through different types of materials, and were reflected by others, such as conductors and dielectrics. The existence of electromagnetic waves was predicted earlier by the Scottish physicist James Clerk Maxwell, but it was Hertz who first succeeded in generating and detecting radio waves.


1900s

[edit] Christian Huelsmeyer
In 1904 Christian Huelsmeyer gave public demonstrations in Germany and the Netherlands of the use of radio echoes to detect ships so that collisions could be avoided. His device consisted of a simple spark gap aimed using a multipole antenna. When a reflection was picked up by the two straight antennas attached to the separate receiver, a bell sounded. During bad weather or fog, the device would be periodically "spun" to check for nearby ships. The system detected presence of ships up to 3 km, and he planned to extend its capability to 10 km. It did not provide range information, only warning of a nearby object. He patented the device, called the telemobiloscope, but due to lack of interest by the naval authorities the invention was not put into production.
Also in 1904, Huelsmeyer received a patent of amendment for ranging that is indirectly related to his device.[4] Using a vertical scan of the horizon with the telemobiloscope mounted on a tower, the operator would find the angle at which the return was the most intense and deduce, by simple triangulation, the approximate distance. This is in contrast to the later development of pulsed radar, which determines distance directly.

[edit] Nikola Tesla
Nikola Tesla, in August 1917, proposed principles regarding frequency and power levels for primitive radar units. In the 1917 The Electrical Experimenter, Tesla stated the principles in detail:
"For instance, by their [standing electromagnetic waves] use we may produce at will, from a sending station, an electrical effect in any particular region of the globe; [with which] we may determine the relative position or course of a moving object, such as a vessel at sea, the distance traversed by the same, or its speed."
Tesla also proposed the use of these standing electromagnetic waves along with pulsed reflected surface waves to determine the relative position, speed, and course of a moving object and other modern concepts of radar.
Tesla had first proposed that radio location might help find submarines (for which it is not well-suited) with a fluorescent screen indicator.

[edit] Naval Research Laboratory
In the autumn of 1922, Albert H. Taylor and Leo C. Young of the U.S. Naval Research Laboratory (NRL) were conducting communication experiments when they noticed that a wooden ship in the Potomac River was interfering with their signals; in effect, they had demonstrated the first continuous wave (CW) interference radar with separated transmitting and receiving antennas. In June, 1930, Lawrence A. Hyland of the NRL in the U.S. detected an airplane with this type of radar operating on 33 MHz.
Simple wave-interference radar can detect the presence of an object, but it cannot determine its location or velocity. That had to await the invention of pulse radar, and later, additional encoding techniques to extract this information from a CW signal. The British and the US research groups were independently aware of the advantages of such an approach, but the problem was to develop the timing equipment to make it feasible. In the early 1930s, Taylor assigned one of his engineers, Robert M. Page, to implement a demonstration system of the pulsed radar idea that he and Young had theorized. Page produced and operated such a pulse system in December 1934[citation needed] using pulses of 25 MHz and 5 μs width. An important development by Young and Page was the Radar Duplexer. This allowed the transmitter and receiver to use the same antenna without destroying the sensitive receiver circuitry.
The Robert Page experiments with pulse radar were conducted at the NRL in 1934 and 1935. On April 28, 1936, their first pulse radar was demonstrated successfully at a range of 2.5 miles on a small airplane flying up and down the Potomac, but by June of that year, the range was extended to 25 miles (40 km). Their radar was based on low frequency signals, at least by today's standards, and thus required large antennas, making it impractical for ship or aircraft mounting.

[edit] Compagnie Générale de Télégraphie Sans Fil (CSF)
In 1927, French engineers Camille Gutton and Pierret experimented with wavelengths going down to 16 cm. Other engineers, Mesny and David, noticed repeatedly since 1931 that an aircraft flying between a transmitter and a receiver would disturb a radio communication. This was the basis of a device put into operational use in 1935 by the Compagnie Générale de Télégraphie Sans Fil (CSF) to detect airplanes flying over a given zone.
In 1934, Henri Gutton (the son of the former, and engineer of the CSF) resumed his father's experiments after initial reports made by the U.S. Naval Research Laboratory in 1930 (see above) and brought improvements to the magnetron. Emile Girardeau [2], the head of the CSF, recalled in testimony that they were at the time intending to build radar systems "conceived according to the principles stated by Tesla". The CSF submitted the French patent (no. 788.795, "New system of location of obstacles and its applications") on July 20 1934, for a device detecting obstacles (icebergs, ships, planes) using pulses of ultra-short wavelengths produced by a magnetron. This is the first patent of an operational radar using centimetric wavelengths. The radar was tested from November to December 1934 aboard the cargo ship Oregon, with two transmitters working at 80 cm and 16 cm wavelengths. Coastlines were detected from a range of 10-12 nautical miles. The shortest wavelength was chosen for the final design, which equipped the liner Normandie as early as mid-1935 for operational use.

[edit] Robert Watson-Watt
In 1915 Robert Watson-Watt joined the Meteorological Office as a meteorologist. Working at an outstation at Aldershot, in Hampshire, Britain, he developed the use of radio signals generated by lightning strikes to map out the position of thunderstorms. The difficulty in pinpointing the direction of these fleeting signals led to the use of rotating directional antennas, and in 1923 the use of oscilloscopes in order to display them. An operator would periodically rotate the antenna and look for "spikes" on the oscilloscope to find the direction of a storm. At this point the only missing part of a functioning radar was the transmitter.
By 1934 Watson-Watt was well established in the area of radio as head of the Radio Research Station at Ditton Park near Slough. He was approached by H.E. Wimperis from the Air Ministry, who asked about the use of radio to produce a 'death ray', after hearing Germans claims to have built such a device. Watt quickly wrote back that this was unlikely, and he pointed out that in the absence of progress, meanwhile attention is being turned to the still difficult, but less unpromising, problem of radio detection and numerical considerations on the method of detection by reflected radio waves will be submitted when required. Watson-Watt and his assistant Arnold Wilkins published a report on the topic on February 12, 1935, titled The Detection of Aircraft by Radio Methods.

The Daventry Experiment 26 February 1935, set up by A.F.Wilkins and his driver, Dyer, to demonstrate the feasibility of RADAR.
On February 26, 1935 Watson-Watt and Wilkins demonstrated a basic radar system to an observer from the Air Ministry Committee the Detection of Aircraft. The previous day Wilkins had set up receiving equipment in a field near Upper Stowe, Northamptonshire, and this was used to detect the presence of a Handley Page Heyford bomber at ranges up to 8 miles (13 km) by means of the radio waves which it reflected from the nearby Daventry shortwave radio transmitter of the BBC, which operated at a wavelength of 49 m (6 MHz). This convincing demonstration, known as the Daventry Experiment, led immediately to development of radar in the UK.

[edit] Allen B. DuMont
In 1932, Allen B. DuMont proposed a "ship finder" device to the United States Army Signal Corps at Fort Monmouth, New Jersey, that used radio wave distortions to locate objects on a cathode ray tube screen. The military asked him, however, not to take out a patent for developing what they wanted to maintain as a secret, and so he is not often mentioned among those responsible for radar. He did, however, go on to develop long-range precision radar to aid the Allies during WWII. As a consequence the French Government knighted him in 1952.

[edit] Soviet Early Radar
On January 3, 1934 Soviet scientists successfully tested experimental radar, developed by joint project between Central artillery Board of Soviet Army (GAU) and Central radio Laboratory (TsRL). A plane, flying at an altitude of about 150 meters, was able to be detected at a distance of around 600/ 700 meters of a radar facility.[citation needed]
Later in the same 1934 year radar devices for AA (anti-aircraft artillery) were created under contract between Central artillery Board of Soviet Army (GAU) and LEFI (Electrical and Physical Institute of Leningrad).[citation needed]
On July, 1934 an experimental radar station called "Rapid" was tested near by Leningrad by engineers of LEFI (Electrical and Physical Institute of Leningrad) under contract with AD (air defence) Board of Soviet Army.[citation needed]

[edit] Dutch early radar
Several years before Watson-Watt, Dutch scientists Weiler and Gratema were inspired by queries about "death rays" from their military, to start developing radar. They were well advanced by May 1940, and had built four working prototypes of centrimetric gunlaying radar operating at a wavelength of 50 cm and a practical range of 20 km[5]. Technically far more sophisticated than British early warning radar of the time, it was not operationally integrated into the armed forces. As the Luftwaffe destroyed the Dutch air force on its airfields, landed thousands of airborne troops on the seat of government, and laid waste to the city of Rotterdam, radar operators could only track their planes. Says Max Staal: "frustratingly, we had nothing to shoot at them with". Some scientists escaped to Britain before the Dutch capitulation on May 14, 1940, taking with them prototypes that aided the development of the British-American centrimetric radar[6][7].

[edit] Hans Hollmann
Meanwhile in Germany, Hans Hollmann had been working for some time in the field of microwaves, which were to later become the basis of almost all radar systems. In 1935 he published Physics and Technique of Ultrashort Waves, which was picked up by researchers around the world. At the time he had been most interested in their use for communications, but he and his partner Hans-Karl von Willisen had also worked on radar-like systems.
In the autumn of 1934 their company, GEMA, built the first commercial radar system for detecting ships. Operating in the 50 cm range it could detect ships up to 10 km away. This device was similar in purpose to Huelsmeyer's earlier system, and like it, did not provide range information.
In the summer of 1935 a pulse radar was developed with which they could spot a light cruiser, the Königsberg, 8 km away, with an accuracy of up to 50 m, enough for gun-laying. The same system could also detect an aircraft at 500 m altitude at a distance of 28 km. The military implications were not lost this time around, and construction of land and sea-based versions took place as Freya and Seetakt.

[edit] World War II
At the start of World War II both the United Kingdom and Germany knew of each other's ongoing efforts in their "battle of the beams". Both nations were intensely interested in the other's developments in the field, and engaged in an active campaign of espionage and false leaks about their respective equipment. By the time of the Battle of Britain, both sides were deploying radar units and control stations as part of integrated air defense capability. However, German radars could not assist in offensive role and the Luftwaffe did not sufficiently appreciate the importance of British radar stations as part of RAF's air defense capability, contributing to their failure.
Research had been initiated by Sir Henry Tizard's Aeronautical Research Committee in 1935 and, from 1940, was based at the Telecommunications Research Establishment (TRE). But much of the credit belongs to Watson-Watt, head of the team working at Bawdsey Manor in Suffolk, who turned from the technical side of radar to building up a usable network of machines and the people to run them. After watching a demonstration in which his radar operators were attempting to locate an "attacking" bomber, he noticed that the primary problem was not technological, but worker overload. By 1940 Watt had built up a layered organization that efficiently passed information along the chain of command, and was able to track large numbers of aircraft and direct defenses to them.

[edit] UK
See also: List of World War II British naval radar

[edit] Chain Home
Shortly before the outbreak of World War II several radar stations known as Chain Home (or CH) were constructed along the South and East coasts of Britain, based on the successful model at Bawdsey. As one might expect from the first radar to be deployed, CH was a simple system. The broadcast side was formed from two 300 ft (100 ;m) tall steel towers strung with a series of antennas between them. A second set of 240 ft (73 m) tall wooden towers were used for reception, with a series of crossed antennas at various heights up to 215 ft (65 m). Most stations had more than one set of each antenna, tuned to operate at different frequencies.
Typical operating conditions were:
FREQUENCY: 20 to 30 MHz (15 to 10 metres).
PEAK POWER: 350 kW (later 750 kW).
PULSE REPETITION FREQUENCY: 25 and 12.5 pps.
PULSE LENGTH: 20 μs.
The CH radar was read with an oscilloscope. When a pulse was sent out into the broadcast towers, the scope was triggered to start its beam moving horizontally across the screen very rapidly. The output from the receiver was amplified and fed into the vertical axis of the scope, so a return from an aircraft would deflect the beam upward. This formed a spike on the display, and the distance from the left side –measured with a small scale on the bottom of the screen– would give the distance to the target. By rotating the receiver goniometer connected to the antennas to make the display disappear, the operator could determine the direction to the target (this is the reason for the cross shaped antennas), while the size of the vertical displacement indicated something of the number of aircraft involved. By comparing the strengths returned from the various antennas up the tower, the altitude could be determined to some degree of accuracy.
CH proved highly effective during the Battle of Britain, and is often credited with allowing the RAF to defeat the much larger Luftwaffe forces. Whereas the Luftwaffe had to hunt all over to find the RAF fighters, the RAF knew exactly where the Luftwaffe bombers were, and could converge all of their fighters on them. In modern terminology, CH was a force multiplier, allowing the RAF fighters to operate more effectively as if they were a much larger force operating at the same effectiveness as the Germans. In addition, the CH system allowed pilots to rest on the ground instead of flying continuous 'standing patrols', and only needing to 'scramble' (take off) when the air threat was imminent. This not only reduced pilot's workloads, but also reduced wear on engines, as well as reducing unnecessary petrol consumption.
Very early in the battle the Luftwaffe made a series of small raids on a few of the stations, including the Bawdsey research and training station, but they were returned to operation in a few days. In the meantime the operators took to broadcasting radar-like signals from other systems in order to fool the Germans into believing that the systems were still operating. Eventually the Germans gave up trying to bomb them. The Luftwaffe apparently never understood the importance of radar to the RAF's efforts, or they would have assigned them a much higher priority – even a concerted effort would not have had much effect on the transmitters as their structure made them very resistant to blast which passed through the spaces in the metal lattice.
In order to avoid the CH system the Luftwaffe adopted other tactics. One was to approach Britain at very low levels, below the sight line of the radar stations. This was countered to some degree with a series of shorter range stations built right on the coast, known as Chain Home Low (CHL). These radars had originally been intended to use for naval gun-laying and known as Coastal Defence (CD), but their narrow beams also meant they could sweep an area much closer to the ground without seeing the reflection of the ground (or water) –known as clutter. Unlike the larger CH systems, CHL had to have the broadcast antenna itself turned, as opposed to just the receiver. This was done manually on a pedal-crank system run by Women's Auxiliary Air Force until more reliable motorized movements were installed in 1941.

[edit] Ground Controlled Intercept
Similar systems were later adapted with a new display to produce the Ground Controlled Intercept stations in January 1941. In these systems the antenna was rotated mechanically, followed by the display on the operator's console. That is, instead of a single line across the bottom of the display from left to right, the line was rotated around the screen at the same speed as the antenna was turning.
The result was a 2-D display of the air around the station with the operator in the middle, with all the aircraft appearing as dots in the proper location in space. These so-called Plan Position Indicators (PPI) dramatically simplified the amount of work needed to track a target on the operator's part. Such a system with a rotating, or sweeping, line is what most people continue to associate with a radar display.

[edit] Airborne Intercept
Rather than avoid the radars, the Luftwaffe took to avoiding the fighters by flying at night and in bad weather. Although the RAF was aware of the location of the bombers, there was little they could do about them unless the fighter pilots could see the opposing planes.[citation needed]
This eventuality had already been foreseen, and a successful programme by Edward George Bowen in 1936 (likely at the urging of Tizard) developed a miniaturized radar system suitable for aircraft, the so-called Airborne Interception (AI) set. At the same time Bowen developed radar sets for aircraft to detect submarines, the Air to Surface Vessel (ASV) set, making a significant contribution to the defeat of the German U-boats.[citation needed]
Initial AI sets were available in 1939 and fitted to Bristol Blenheim aircraft, replaced quickly with the better performing Bristol Beaufighter. These quickly put an end to German night- and bad-weather bombing over Britain. Mosquito night intruders were fitted with AI Mk VIII and later derivatives which, along with a device called "Serrate" to allow them to track down German night fighters from their Lichtenstein B/C and SN2 radar emissions, as well as a device named "Perfectos" that tracked German IFF, allowed the Mosquito to find and destroy German night fighters. As a countermeasure the German night fighters employed Naxos ZR radar detectors.[citation needed]

[edit] Centimetric radar
The next major development in the history of radar was the invention of the cavity magnetron by John Randall and Harry Boot of Birmingham University in early 1940.[citation needed] This was a small device which generated microwave frequencies much more efficiently than previous devices, allowing the development of practical centimetric radar, which operates in the radio frequency band from 3 to 30 GHz.[citation needed] Centimetric radar allowed for the detection of much smaller objects and the use of much smaller antennas than the earlier lower frequency radars, and the cavity magnetron is the single most important invention in the history of radar.[citation needed] It was given free as a gift to the US in 1940 together with several other inventions such as jet technology, partly to encourage them to enter the war on the side of the British.[citation needed] Simultaneously, Robert M. Page invented the duplexer switch at the U.S. Naval Research Laboratory, allowing a pulse transmitter and receiver to share the same antenna without destabilizing the sensitive receiver.[citation needed]
The combination of the magnetron, the duplexer switch, small antennas and high resolution allowed small high quality radars to be installed in aircraft. They could be used by maritime patrol aircraft to detect objects as small as a submarine periscope, which allowed aircraft to attack and destroy submerged submarines which had previously been undetectable from the air.[citation needed] Centimetric contour mapping radars like H2S improved the accuracy of Allied bombers used in the strategic bombing campaign. Centimetric gun laying radars were much more accurate than the older technology. They made the big gunned Allied battleships more deadly and along with the newly developed proximity fuze made anti-aircraft guns much more dangerous to attacking aircraft. The two coupled together and used by anti-aircraft batteries, placed along on the German V-1 flying bomb flight paths to London, are credited with destroying many of the flying bombs before they reached their target.[citation needed]
The British need to produce the magnetron in large quantities was so great that Edward George Bowen was sent as the radar expert in the Tizard Mission to the USA in 1940, which resulted in the creation of the MIT Radiation Lab to develop the device further. Half of the radar deployed during World War II were designed at the RadLab, including over 100 different radar systems costing $1.5 billion.[citation needed]

[edit] Germany
German developments mirrored those in the United Kingdom, but it appears radar received a much lower priority until later in the war.[citation needed] The Freya radar was much more sophisticated than its CH counterpart[citation needed], and by operating in the 1.2–m wavelength (as opposed to ten times that for the CH) around 250 MHz the Freya was able to be much smaller and yet offer better resolution.[citation needed] Yet by the start of the war only eight of these units were in operation, offering much less coverage.[citation needed]
Compared to the British PPI systems, the German system was far more labour intensive.[citation needed] This problem was compounded by the lackadaisical approach to command staffing.[citation needed] It was some time before the Luftwaffe had a command and control system nearly as sophisticated as the one set up by Watson-Watt before the war.[citation needed]
This state of affairs did not last long. By 1940 the RAF's night raids were becoming a nuisance, and action was finally taken to address the problem. Josef Kammhuber was promoted to become the General of the Night Fighters and set about creating a network of Freya radar stations in a chain of "cells" through Holland, Belgium and France. Known as the Kammhuber Line, each cell of the network contained a radar and a number of searchlights, as well as one primary and one backup night fighter. When a bomber was detected flying into the cell the searchlights were directed by the radar to pick it up, at which point the night fighter could see the now-lit bomber.[citation needed]
While somewhat effective, the system was useless during bad weather or other times where the light would be blocked.[citation needed] In order to address this problem, the Würzburg radar was developed. Würzburg was a short-range radar mounted on a highly directional parabolic antenna that was sensitive in only one direction. This made it useless for finding the targets, but once guided to one by an associated Freya it could track it with extreme accuracy: later models were accurate to 0.2 degrees or less.[citation needed]
Two Würzburgs were assigned to each cell, one to track the target bomber, and another the night fighter. By plotting the location of both aircraft on a common plotting table, radio operators could direct the fighter manually to the target. The downfall of the Kammhuber Line was that it could only track a single target per Würzburg.[citation needed] When the British learned of this, they directed operations such that all their bombers concentrated on crossing the line en masse over as few cells as possible. This bomber stream introduced in mid 1942 meant that as a raid developed, only a few night fighters could be directed into the raid at any one time, and bomber losses dropped to a handful per raid.[citation needed]

[edit] Airborne radars

Bf 110 night fighters
The use of the accurate Freya and Würzburg allowed the Germans to have a somewhat more lackadaisical approach to the development of an airborne radar.[citation needed] Unlike the British, whose inaccurate CH systems demanded some sort of system in the aircraft, the Würzburg was accurate enough to allow them to leave the radar on the ground.[citation needed] This came back to haunt them when the British figured out their system, and the development of an airborne system became much more important.[citation needed]
Early Lichtenstein BC units were not deployed until 1942, and as they operated on the 2–m wavelength (150–MHz) they required large antennas. By this point in the war the British had become experts on jamming German radars, and when a BC-equipped Ju 88 night fighter landed in Britain one foggy night, it was only a few weeks before the system was rendered completely useless. By late 1943 the Luftwaffe was starting to deploy the greatly improved SN-2, but this required huge antennas that slowed the planes as much as 50–km/h. Jamming the SN-2 took longer, but was accomplished. A 9–cm wavelength system known as Berlin was eventually developed, but only in the very last months of the war.[citation needed]

[edit] US

1946 newsreel
After early U.S. work on radar conducted in the twenties at the Naval Research Laboratories, the success of Robert Page's pulsed radar experiment in 1934 redirected the attention of the Signal Corps, who had been focusing more on use of sound and heat to detect aircraft. Expertise in radio equipment design by the signal corps led to rapid development of an early type of VHF radar at Fort Monmouth and Camp Evans in New Jersey for use with coastal artillery .

Radar arrangement on the aircraft carrier Lexington, 1944
By 1940 when the British and US began technology exchanges, the British were surprised to learn they were not unique in their possession of practical pulse radar technology. The U.S. Navy's pulse radar system, the CXAM radar was found to be very similar in capability to their Chain Home technology. The British were much further ahead on microwave research necessary for the second generation of military radars. Although the US Navy had produced by 1940 an experimental 10–cm radar, they were stymied by the problem of insufficient transmitter power. On entry to World War II, the army and navy had working first generation radar units in front line units, and this technology was relied on throughout the war. The army's type SCR-270 radar detected the Japanese planes attacking Pearl Harbor at a range of 132 miles (212 km), although this information was not used effectively at the command level. After the war this unit was employed in the first application of radar in astronomy by bouncing radio waves off the Moon in 1946.
Although the US had developed pulsed radar systems independent of the British as had the Germans, there were serious weaknesses in their efforts - the greatest of which was the lack of integration of radar into unified air defense system. Here the British were without peer. The result of the Tizard Mission in 1940 was a major step forward for utilization of radar technology, both in the transfer of the organizational knowledge that Watson-Watt had worked out as well as the British microwave technology. In particular, the cavity magnetron was the answer the US was looking for, and it led to the creation of the MIT Radiation Lab, a major center for research employing almost 4,000 people at its peak during the Second World War.
It was in 1942 that the neologism and acronym RADAR was coined by the U.S. Navy. The acronym RADAR is still in use by the US Navy, and as a mnemonic device to describe its components, they have come up with a new acronym, ARMPIT (Antenna, Receiver, Modulator, PowerSupply, Indicator, Transmitter).

[edit] Japan

Nakajima J1N night fighter with FD-2 nose radar
Well prior to World War II, Japan had knowledgeable researchers in the technologies necessary for radar but due to lack of appreciation of radar's potential, and rivalry between army, navy and civilian research groups, Japanese technology was 3 to 5 years behind that of the US during the war. The Japanese captured a British type gun laying radar in Singapore as well as an American SCR-268 and SCR-270 when they overran the Philippines.[citation needed] In August 1942, US marines captured a Japanese Navy Type 1 model 1 radar, and though judged to be crude even by the standards of early US radars, the fact the Japanese had any radar capability came as a surprise.[citation needed]
One leader in radar technology was Hidetsugu Yagi, a researcher of international stature who was working on applications of power transmission via microwave in the early 1930s.[citation needed] Though his project was overly ambitious, the work he did was directly applicable to advanced microwave radars. The papers he delivered in the late 20s in the US on antennas and magnetron design were closely studied by US researchers.[citation needed] His work was given so little attention by Japanese military researchers that when the Japanese captured the British radar unit in Singapore, at first they were unaware that the "Yagi" antenna mentioned in captured manuals referred to a Japanese invention. Although progress was rapid after the value of radar was better appreciated, research continued to be impeded by inter-service rivalry and new units, though capable, were too late to influence the outcome of the war.[citation needed] Radar was used by the army for gun laying and aircraft detection, by the navy for detection of air and sea threats on all major capital ships, including use of centimetric units in 1944.[citation needed] Towards the end of the war, units were sufficiently miniaturized for airborne intercept (FD-2) radar on J1N1-S Gekko night fighters and airborne ship detection radar in G4M2 "Betty" bombers and Kawanishi H8K patrol planes.

[edit] Canada
Little radar research was done in Canada prior to the start of WW2. However, in 1939 the National Research Council of Canada was tasked with developing a Canadian designed radar system. After the fall of France in June 1940, radar research was given the highest possible priority, leading to the development and deployment of a series of radar systems, including the CSC type and SW1C naval radars, which were operationally deployed on RCN ships in 1941, placing Canada into the forefront of naval radar deployment.[8]

[edit] Cold War
After World War II the primary "axis" of combat shifted to lie between the United States and the Soviet Union. In order to provide early warning of an attack, both sides deployed huge radar networks of increasing sophistication at ever-more remote locations. The first such system was the Pinetree Line deployed across Canada in the 1950s, backed up with radars on ships and oil platforms off the east and west coasts. The Pinetree Line was a simple system and was vulnerable to jamming, so the more sophisticated Mid-Canada Line (MCL) was set up to supplant it. However, the MCL was not considered to be militarily very useful, and the DEW Line started construction soon after, in the high Arctic. Construction of the DEW line is still considered one of the great logistics and civil engineering projects of the 20th century. In the late 1950s, the Ballistic Missile Early Warning System was added to warn of ICBM launches.

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