Radar

radar antenna

radar (English: RA dio D etection A lp R concerned, German: Discovery and ranging by means of radio waves) is the name for a discovery or a locating method as well as equipment used for it, electromagnetic waving (usually microwaves in MHz andGHz range) bundled as primary signal sends, afterwards from objects reflected “echoes “as secondary signal receives and to different criteria evaluates to usually make in order a detection possible. So information objects removed over far can be won. There are different radar principles, seealso harmonious radar and over horizon radar.

Different information can be picked out from the received waves:

  • from the angle in relation to the north the relative direction of the focused object results
  • from the time between mailing and receiving can the distance be computed(see speed of light)
  • from the reflected frequency it can be computed whether and how the object approaches relative to the observer or far away (see Doppler effect)
  • from pursuing the individual measuring procedures results the course already put back and/or.Distance of the object
  • when good dissolution the radar even pictures of the object can be produced.

The used word radar is an English acronym from “RA dio D etection A lp r concerned " (about: Finding and ranging with Radiowellen).The original designation radar coming from the German was replaced after the Second World War in the Federal Republic of Germany by the term radar. In the GDR in the technical language further of radar one spoke.

Radarmonitor in der Flugüberwachung
Radar monitor in the air traffic control

table of contents

History

the radar hood, which protects the radar DRBI 23 (July 1998).

Heinrich Hertz determined 1886 with the experimental proof from electromagnetic waves that Radiowellen are reflected by metallic articles.

Years later the Indian Jagadish Chandra Bose Hertz repeated elevenAttempts in Calcutta, this time however with a shorter wavelength than Hertz. Due to these attempts Bose developed among other things transverse electromagnetic wave.

1904 the German high frequency technician Christian Hülsmeyer accomplished the first attempts of the detection by means of Radiowellen. Its Telemobiloskop could to 30 measures and became the running time of waves, which were back-thrown by a ship. April 1904 to the patent announced.

The title of the patent specification No. 165546 read:

Procedure, in order removed metallic articles by means of electrical waves for an observer to announce.
Available invention has a device to the article, by which the approximation and/or movement of distant metallic articles (ships, courses or such a thing) is announced to an observer by means of electrical waves by hear or visible signals [...]

the 23-jährige Christian Hülsmeyer wanted actuallyTeachers become. With experiments in the physics hall of Bremen of the teacher min acre he came on one - for the development of radar technology - innovative idea.

With experimenting with the Hertz' mirror attempts Hülsmeyer stated that a transmitter sent and metal surfaces back-thrownelectrical waves for the determination of distant metallic objects to be used can - its special interest applied for ships.

By Hülsmeyers patent 1911 in the USA the basic principles of the radar of the Science Fiction author and inventor Hugo Gernsback in its became probably uninfluenced Science Fiction novel Ralph 124C 41+ outlines. The novel is based in its original version on a subsequent series, which in the technique magazine decaying Electrics was published between April 1911 and March 1912.

The search for new physical principles for solution of theProblem of the recognition and locating of air and surface targets in the middle of the 1930er led almost at the same time years in several countries to the development of radar technology (radar, radiolokacia).

history of the radar development in Germany

the break-through for broad application came forradar technology only in the Second World War. Dr. Rudolf Kühnhold, the scientific director of the message test department of the German navy, advanced the development crucially. 1934 succeeds to Dr. Rudolf Kühnhold in the Kieler port the first attempts with one of itdeveloped apparatus, so-called Dezimeter telegraphy - the equipment and/or. DeTe equipment. With its attempts it could to be located not only as planned ships, but also over the port flying airplanes.

Still was the distance, at which the radar worked, for the military usesuitably, but in the following months the development preceded fast. Already in October rangings arrive over approximately 40 kilometers.

In the Second World War radar technology in the naval warfare, above all in addition, in aerial warfare attained great importance andusually in connection with anti-aircraft positions one used. The first militarily successful radar-led interception mission of history took place to 18. December 1939, when British bombers approached to the attack on German warships in the German bay. After the detection of the bombersheavy losses added ascending interceptor to the bombers.

A manufacturer of radar device was the GEMA (society for electroacoustic and mechanical apparatuses ltd.) with seat in Berlin. The GEMA had also a branch in Wahlstatt/Schlesien (with Liegnitz). The GEMA shifted toEnd of the war their production after east Holstein and there after Pelzerhaken and Lensahn. Up to the end of war the far order funkmessgeräte remained producing and repair. In Pelzerhaken the buildings of the means of communication laboratory became and/or. the means of communication attempt command used. In Lensahnone referred realm-grain-resounds and ehem. Carrot shred factory. In Pelzerhaken starting from 1934 the GEMA had already before operated the development of its funkmessgeräte. Hans's Karl baron von Willisen and Paul Günther Erbslöh and tested here Freya, giant, water man developed and alsoSea-clock and sea-kind equipment. With the end of war the GEMA was dissolved as Rüstungsbetrieb. The Secret service led the disassembly and the evacuation as reparation.

history of the radar development in England

Chain Home an der englischen Küste
chain Home at the English coast

during itself thoseRadar development in Germany at the beginning with the recognizing of ship goals busy, was in England the recognition of airplanes the starting point of the development.

Already in the ionospheres - research one had used radio impulses and from the running time up to the arrival of the reflectedSignal the height of the ionosphere determines. This method was developed further now for the radiolocation. The director/conductor of the radio research station in Slough Robert wading on Watt and its coworker of the physicists Arnold Wilkins put to 12. February 1935 their report recognizing and places ofAirplanes by radio forwards, in which they already described all substantial fundamentals of the radar.

Already to 26. February 1935 was accomplished the first field test. The BBC - Transmitter in Daventry would send a signal with 49 m wavelength. This was on thoseWingspan of usual bomber airplanes co-ordinated, which lay with approximately half of this length and represented thus half wave dipoles. Of it good reflection characteristics were expected. A mobile slave station, equipped with time at that time a very modern cathode ray oscilloscope, was in approx. 1Mile distance. Over this area flying test flight things actually produced by the radio waves reflected at its trunk an additional Leuchtpunkt on the screen of the oscilloscope. The airplane could already with this first test up to a distance of 13 kmare pursued.

After these successful test results the English radar development was begun with high expenditure. Already in January 1936 for all aspects of the radar detection (distance, elevation angle and detection direction) solutions had been found. Even the principle of a goal subsequent radar could do to 20. June 1939 vienna clay/tone Churchill to be practically demonstrated.

In the year 1937 one began to install at the east coast of the British island chain of 20 coastal radar positions, the so-called chain Home. She worked at 10 to 13.5 m wavelength (22-30 MHz), would send 25And a range of 200 km had pulses per second with 200 KW of achievement. Starting from Karfreitag 1939 was this radar chain in the 24-Stunden continuous operation.

The installation of the high masts remained naturally not hidden to the Germans. At the beginning of of May and in August 1939they undertook therefore two electronic clearing-up flights with the airship LZ 130 count Zeppelin II over the English Channel, in order to explore the conditions of English radar technology. They found however no radar signals. This was because of the fact that the German radar development within the rangefrom 1,5 to 0.5 m wavelength took place, which radar stations at the English channel coast, which were since Karfreitag 1939 in use, which used wavelength for German engineers completely wrong range from 10 m.

Chain Home had high range,however no low fliers could discover. Therefore additionally chain Home Low, a low-altitude flight radar chain at 80 km range was installed with 1,5 m wavelength (200 MHz).

The radar chain proved as important advantage in the air battle around England, there thoseAttacks to be in time recognized and the defense better coordinated knew.

Immediately also radar device for the employment in airplanes was developed. After the first devices were only moderately useful due to their wavelength of minimum 50 cm, succeeded to two British researchersto 21. February 1940 the structure of the first laboratory instrument of a Magnetrons for the production of 10 cm waves. From this the H2S became - equipment develops, an on-board radar for airplanes, with which the outlines of the landscape were represented as on a map. Thatfirst employment took place to 30.- 31. January 1943 with a bomb attack on Hamburg.

There was a simple means, in order to disturb the use from radar to. Both sides, Germany and England, had discovered and held this means independently theseDiscovery then top secret, in order not to tell thereby to the opposite side the method, how again the own radar could be disturbed. It concerned here tin-foil tape (chaff (radar deception) mentioned), those cut to the half wavelength of the used radar deviceand airplanes in large quantity were thrown off. Were then the Englishmen, this method then still with the operation Gomorrha, the bomb attack on Hamburg to 24. July 1943, used. 92 millions strips, which corresponds, became40 tons, thrown off. The development of a suitable remedy had success on German side then. Peppering louse - equipment could determine the speed of the radar target on the basis the Doppler effect. Slowly flying or standing objects, like the tin-foil tapes, were then simply faded out.

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History of the radar development in the Soviet Union

the fact of its own development in the Soviet Union is hardly mentioned by western sources, is characterised this by a number of interesting solutions. The Soviet radar development took place under the conditions of the internationalIsolation of the USSR and later the evacuation of construction and production capacities eastward.

The cradle of the Soviet radar (radiolokacia) was located in Leningrad/ Petersburg, where Popow 1895 had transferred the first radio signals. Into the 1920er years Russian furnished andUkrainian scientists theoretical payments in advance concerning the application of the reflecting detection by means of electromagnetic waves. Bontsch Brujewitsch, arene mountain and Wwedenski examined the reflection behavior of electromagnetic waves. Via Mandelstam and Papaleksi phasometrische rangings took place for the determination of the height of the ionosphere with electromagnetic impulses. For the Femsehtechnikgenerator and modulator tubes were developed, which could find also for the new technology application. In Charkow attempts took place, which led later to the application of the Magnetronverfahrens to the production of decimillimetric waves.

The idea of the use from radio waves to the discovery and Standortbestirnmungfrom missiles developed at the same time in two administrations of the People's Commissariat for defense - in the military-technical administration 1930 in the plan for reconnaissance equipment of the anti-aircraft artillery and in the administration air defense 1932/33 for the improvement of the air clearing-up. End of 1933 became on initiative of theMilitary engineer M.M.Lobanow in centers the radio laboratory investigations for reflecting detection begun with decimetric waves. Under the direction of J.K.Korowin an airplane with an experimental assembly was located for the first time, which consisted of 60-cm-Dauerstrichsender, one superregenerativ receiver and 2 parabolic antennas for sending and receipt. In January 1934of the Akadermiemitglieds A.F.Joffe a consultation of considerable specialists took place under line, who supported the ideas of engineer P.K.Ostschepkow for a system of the air clearing-up by means of electromagnetic waves. In the “magazine of the air defense”, number 2/1934, Ostschepkow published its thoughts over a reconnaissance systemthe air defense, the advantages of the Irnpulsmethode for the detection of airborne targets and the idea of a panorama station, which determines distance and firing angle of a missile at the same time.

• RUS-1, the electromagnetic “curtain” still 1934 began extensive work for the realization of the radiolocation under usethe continuous line radiation. In August 1934 the experimental assembly was tested “rapidly”, those from a 200-W-Sender on the wavelength 4.7 m and two in the distance of 50 and/or. 70 km distance developed receivings existed. The transit flight of an airplane in 5200 m heightcould be registered on the basis the floating, which by interference of direct and reflected wave were formed, reliably. From this later the system “Rewen” developed, which 1939 were transferred as RUS-1 (radioulowitel samoljotow) to the equipment of the Red Army. To beginning of war 194141 sets RUS-1 were assigned for the education of an electromagnetic “curtain” in the air defense of Moscow and Lenin degree.

• Work, those began impulse radar station RUS-2 at the beginning of 1935 for the construction of the first Soviet in physical-technical Institut of the Academy of Sciences under the direction of J.B.KobsarewImpulse radar station led. Still in the same year the proof was furnished that one can reach a detection distance of 100 km with impulse equipment on the wavelength of 4 m. Successful attempts with Uda Yagi antennas and the development of special emitter eyes (IG-7 followed,IG-8). Until 1939 so the mobile impulse radar station “Redoute” developed, which was transferred after successful troop testing in July 1940 as RUS-2 to the equipment. In its original variant the RUS-2 consisted of a swivelling cab with the 50-kW-Sender and the transmitting antennaon a motor vehicle ZIS-6, a cab with receiving antenna, receipt equipment and an electron beam tube as display terminal on a motor vehicle GAZ-3A as well as a power supply unit on the plank bed of a further GAZ-3A. The antennas homogeneous for sending and receipt, which were synchronously moved, consisted ofactive emitter, one reflector and five directors for the wavelength of 4 M. With the realization of sending and receiving with only one antenna by means of an antenna changeover switch the entire equipment on a vehicle knew accommodated and the turn upthe antenna to be limited. To beginning of war 1941 15 devices of the a antenna variant were delivered.

The RUS-2 made the discovery of airborne targets at large distance and in all heights flown at that time and the determination of their distance and their azimuth, for the approximate speed possibleand the existence of groups of airplanes (on the basis of the interference) as well as the representation of the air situation in the radius to 100 km. It played a large role during the air defense of Moscow and Lenin degree. In the year 1943 took place the installation friend/enemy interrogator andan elevator measuring accessory on the basis of the goniometer method. 1940-1945 was delivered 607 RUS-2 in different variants, among them also an a antenna variant in transportation crates RUS-2s („Pegmatit “). The impulse radar station RUS-2 was starting point of the development of several generations of mobile and stationary meter wave radar devices in the Soviet Union(P-3, P-10, P-12, P-18, P-14, Oborona-14, Njebo).

· Decimetric wave radar for the Flak the first Soviet decimetric wave plant developed for centers starting from 1935 under the direction of B.K.Schembel in the radio laboratory. Two 2-m-Spiegel, per one for sending and receiving on wavelengths from 21 to 29cm, were next to each other located on a platform. With a radiated output of 8 to 15 W and a receiver sensitivity of 100 µV an airplane in 8 km distance was discovered. With tests on the Krim could the reflection of 100km distant mountains to be observed and for ranging the frequency modulation be used for the first time.

In the year 1937 one introduced the procedure of the signal-same zone for the more exact determination of the angle coordinates by means of rotary dipole. In the following years one became at the creationDirection finder for the Flak in Leningrad and Charkow worked. A whole series of different Magnetrons for the dezimeter and centimeter wave range developed. 1940 invented Degtarjow the reflex klystron.

The construction of a radar complex for the Flak became practically 1940 locked. The complex existedfrom continuous line equipment for the determination of the angle coordinates on the wavelength 15 cm with 20 W achievement and impulse equipment for ranging on the wavelength 80 cm with 15 KW of impulse achievement. Because of the evacuation of the enterprise in the autumn 1941 cameit however not for the admission of series production; one used some test devices in the air defense of Moscow and Lenin degree.

airplane radar

work for the creation of a radar for fighters began 1940. In the test device „Gneis-1 “became in the transmitter a klystron alsothe wavelength 15-16 cm uses, which could not be manufactured however due to the war effects no more. Therefore the Funkmessgerät became „Gneis-2 “for the application in twin-engine airplanes Pe-2 with a tube transmitter of the wavelength 1.5 m and a view distance under the direction of W.W.Tichomirowfrom 4 km develops. The first experimental models existed their acid test in December 1942 with Stalingrad. The admission into the armament took place 1943.

operational areas

Deutsches Zielverfolgungsradar Würzburg-Riese FuMG 65, etwa 1940-43
German tracking radar peppering castle giant FuMG 65, about 1940-43
doppler radar antenna for the Kfz employment
Sturmfront auf einem Doppler-Radar-Schirm
storm front on oneDoppler radar display screen
Sea Based X-Band Radar (SBX) (USA) das weltgrößte X-Band-Radar, hier während Modernisierungsarbeiten in Pearl Harbour im Januar 2006. Es dient ab 2007 dem US-Raketenabwehrsystem National Missile Defense und wird auf den Alëuten bei Alaska stationiert.
Sea Based X-volume radar (SBX) (the USA) the world largest X-volume-radar, here during modernization work in Pearl Harbour in January 2006. It serves the US anti-missile defense system starting from 2007 national Missile Defense and on the Alëuten with Alaska is stationed.

Radar device became for differentIntended purposes develops:

  • Early warning stations, which warn of approaching airplanes, like the Freya radar, either a firm or mobile (vehicle-supported) a radar
  • of radar device for tracking, as “dishes”; see peppering castle giant
  • bomber got on-board radar, around also at night by the soil details to recognize to be able
  • night fightersgot radar, in order at night opposing airplanes to attack to be able
  • Schiffsradar, in order to discover or avoid around collisions hostile ships and airplanes.
  • Weather radar, recognition and detection of bad weather fronts
  • of radar device for the measurement of the speed in the traffic with devices and.A. the companies Multanova and Traffipax.
  • Kfz technology. Since end of the 1990er years are available for vehicles of the elevated middle class and the upper class radar-based spacers. However the market penetration is still relatively thin (approx. 300.000 to 700,000 systems world-wide in the year 2003).The generation change toward economical systems began 2003/2004. Analysts see by the coupled use of such systems with so-called. “Emergency-brake” - functionalities an enormous Wachstumpotenzial of >500.000 systems/year until 2012. Close range functions represent a further area of application. The appropriate frequency permission forthe “hope-fullest” technology (24 GHz, short pulse) was given to at the end of of 2004. However this permission is coupled to some editions, why the Mark leaders (Raytheon, Siemens, etc.) work on technologies for 77-79 the GHz volume.
  • Course technology. With introduction of electronic signal towers anddriving without driver with the courses new ranges of application open. With radar device e.g. frame becomes. recognized whether a vehicle on a railroad overpass remained lying or whether, (with driving without driver in stations), an obstacle before the course falls in the track. Also the speedthe course with radar device highly exact one measures. Appropriate devices become e.g. frames. built by the company Honeywell. They work in the ISM volume at 24 GHz after the Doppler the CW or FMCW procedure.
  • Miniature radar device as movement or level alarm unit
  • scientific research: Mapping of heavenly bodieswith obscure atmosphere like the planet Venus, measurement of the solar system

after the Second World War was added also the steering of radar-controlled weapons such as air defense rockets. In addition the radar was used also for the civilian ship and aviation. Today's passenger aviation would be withoutAir traffic control by radar not conceivablly. Also satellites and Weltraumschrott are supervised today by radar.

When the radar device became more efficient, also the science discovered this technology. Weather radar devices help in the meteorology or on board airplanes with the weather forecast. By means of largerStations can be produced from the soil radar images of the moon, the sun as well as some planets. Turned around also the earth from space can through satellite-close-supports radar device to be measured and investigated.

one differentiates between

technical function with radar devicein principle between pulse and CW-radar device.

Pulse radar equipment sends impulses with a typical length within the lower microsecond range and waits then for echoes. The distance becomes by the formula

< math>

r= {c_0 \ cdot t \ more over 2} </math>

r = distance
C 0 = speed of light
determines t =

time. Depending upon range of the radar device now some micro will receive until milliseconds, before the next impulse is sent. Most well-known areas of application are air traffic control and weather radar. If the antenna turns, can with an appropriate announcementa map of reflecting objects to be produced. By digital signal processing (clutter suppression, MTI) thereby being certain objects can be faded out electronically.Transponders at airplanes can contribute that to the identification, by adding the hitting radar signal with reflecting a characteristic digital sample actively, ofOperator assigned airplane identification, which height above ground and the speed above ground, which are measured of the airplane, code. With appropriate evaluation electronics also the relative speed of the located objects, whose height and also the size determine, leaves itself. Evaluations ofHarmonic waves for the air traffic control permit conclusions on the type of aircraft, which generated the echo. Stationary pulse radar devices reach achievements up to 100 MW as point impulse achievement.

An approach radar at airports sends fan standing perpendicularly one on the other to two, these serves control ofApproach direction and - angles and permits pilots with poor visibility a so-called. Instrument landing. Each deviation from the ideal localizer path is on board indicated to them (so-called. Instrument Landing system, ILS).

The ground-based STCA (Short term Collision Avoidance) system to collision avoidance usesthe air surveillance radar. It computed from speed, position and orientation of flying objects the probability of a close flyby (near measure) or collision of airplanes and warns optically and acoustically the air traffic controller.

pulse-modulated radar

over in pulse-modulated radar devices the high transmitting powersto produce, which for detection z. B. over some 100 km, become z are necessary. B.Magnetrons uses. In addition a Magnetron becomes z. B. by means of high voltage switching tubes (thyratron) pulsed operated. Since in these switching tubes thereby also x-ray developed, ledthis more frequently to radiation damage at in former times insufficiently shielded serving and maintenance staff of military radar device.

Since the transmitter frequency of a Magnetrons can change as a function of temperature and operating condition, the Empfangsfrequenz is derived from the transmitter frequency.

CW-radar

a CW-radar(CW = Continuous Wave, continuous transmitter) z can. B. also for speed measurement to be used. Over an antenna a constant frequency is radiated, which is reflected by the goal (for example a car) and with a certain Doppler shift returns. By a comparison thatsent with the received frequency the speed can be determined. These CW-radar device cannot measure distances. The necessary transmitting powers are very small. The radar device of the traffic police (“radar traps”) is such CW-radar device. A further kind are the “Modulated CW-radar” or FM radar device. Itsend with a constantly changing frequency. The frequency rises either linear, in order with a certain frequency abruptly to the initial value again to drop (saw tooth samples), or it rises and falls alternating with constant rate of change. By the linear change of the frequencyand constant sending is possible it to determine apart from the difference speed between transmitters and object also at the same time for their absolute distance from each other. Radar altimeters of airplanes and spacer warning devices /-radare in cars work according to this principle.

see also

literature

  • Harry of Kroge: GEMA Berlin- Birth place of the German active water-borne sound and radiolocation technology, 1998, ISBN 3-00-002865-X
  • Robert Buderi: The invention that changed the world. Simon & shoemaker, New York 1996, ISBN 0-684-81021-2
  • Fritz Trenkle: The German radar procedures until 1945. Hüthig, Heidelberg 1986, ISBN 3-7785-1400-8
  • Brian Johnson: Top secret: Science and technology in the Second World War. Viennese publishing house, Vienna 1978, ISBN 3-89350-818-X
  • Ulrich core: The emergence of the radar procedure. To the history of radar technology until 1945. Thesis, Stuttgart 1984
  • David Pritchard: By space and time: Radar development and - employment1904-1945. Stuttgart 1992
  • franc Reuter: Radar. The development and the employment of the radar procedure in Germany up to the end of the Second World War. Opladen 1971
  • M.M.Lobanow: The beginnings of the Soviet radar , publishing house Soviet bunk radio (ru), Moscow 1975
  • J.D.Schirman among other things Theoretical basesthe radiolocation , military publishing house of the GDR, Berlin 1977

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