Radiolocation

What is radiolocation?

Location - determining the location of an object. Depending on the type of signals used, its types are distinguished:

optical location, thermal location, sound location, sonar and, in fact, radar.

Radiolocation can also be defined as a scientific and technical discipline that studies and creates devices and methods designed to obtain data about objects and terrain using radio waves. A close and partially overlapping term is radio navigation, a scientific and technical discipline engaged in the study and creation of radio engineering tools and methods of navigation when driving moving objects.

If some kind of device is used for location, then it will be called a locator, with an appropriate prefix (echolocation, sonar, etc.).

Depending on whether the locator receives the object's own signal or the probing signal emitted by the locator itself, the location can be referred to as passive and active.

And in accordance with this rule, there are 2 types of radar:

Passive radar, or passive radar surveillance method. It is based on receiving the object's own radiation or radiation reflected by the object from another source. Such systems have only receivers in their composition and do not create a probing signal, for this reason they are the most noise-resistant in comparison with other types.

The initial signal The signal reflected from the object Reflective object

Active. It is used to detect or track objects that are not themselves the source of the radio signal. With this method, the radar itself emits a request or probing signal, and then receives a response.

Also, active radar has 2 types:

With an active response. It assumes the presence of a responder radio transmitter on the object, which emits radio waves in response to the request signal. It is used, for example, for remote radio control or for identification of friend or foe. The response signal may also contain additional information (type of object, remaining amount of fuel, etc.)

With a passive response. In this method, the radar emits a probing signal and receives it after reflection from the target as a response. The characteristics of the object are determined depending on the parameters of the signal received after reflection.

Probing signal  Response signal  Reflective objec

Back in 1897, during experiments on radio communication between the ships "Europe" and "Africa" in the Baltic Sea, Alexander Stepanovich Popov registered the effect on the level of the received signal exerted by a ship crossing the radio path. In the future, this phenomenon was used in radar systems operating "at clearance" and used, for example, to guard the entrance to the harbor.

Then in 1922, American military engineers conducted experiments on radio communication across the Potomac River, at that time a ship passed along the river, and the connection was interrupted, just as in the case recorded by A. S. Popov, which prompted the idea of using radio waves to detect moving objects by interference of undamped oscillations.

Alexander Stepanovich Popov 1859 - 1905

The first radars

Radar (radio detection and ranging), is a system used to detect the position of objects and obtain data about them. The English term appeared in 1941, and eventually passed into the category of a separate word.

Radar example

The first patent for the radar was received by the German Christian Hulsmayer. After familiarizing himself with Heinrich Hertz's discovery that electromagnetic waves are reflected from metal surfaces, Helsmeier focused his attention on a system that would use this phenomenon to prevent ship collisions, in 1902 he successfully tested his method on the Rhine River, and in 1904 received a patent for his device.

The device, called a "telemobiloscope", unlike modern radars, was not able to determine the distance to the target directly, but it coped well with determining the presence of distant objects, such as the same ships.

Christian Hulsmeier 1881 - 1957

Replica of a telemobiloscope from the museum in Munich

Despite the existence of radar, in general, the technology has not been actively used for a long time. The first practical results in radar were obtained by different countries almost at the same time - in the first half of the 1930s. The development of aviation at the same time became a serious incentive for studying technology.

The first radars in the USSR

In the USSR in 1930, Soviet scientists Leonid Mandelstam and Nikolai Papaleksi developed a theory of measuring distances using wave interference. Then, in 1934, engineers from the research groups led by P. K. Oshchepkov and B. K. Shembel, using the Rapid experimental setup developed by them, experimentally proved for the first time in the USSR the practical possibility of radio detection of an aircraft using an electromagnetic wave reflected from it.

Pavel Kondratievich Oshchepkov 1908 - 1992

Boris Konstantinovich Shembel 1900 - 1987

After an unplanned suspension in research, the reason for which was the arrest of Oshchepkov in 1937 on charges of counterrevolutionary activities in connection with the "Chukhachevsky case", a year later, based on the ideas of P. K. Oshchepkov, the experimental installation "Rhubarb" was developed, which later served as a prototype for the world's first serial radar RUS-1 (aircraft radio trap). The USSR entered service in 1939, and a year later the RUS-2 radar entered service, which used separate director antennas (receiving and transmitting) located on the cabins of cars. Its modification "Redoubt", which had rotating antennas, was widely used during the Great Patriotic War.

RADAR РУС-1

RADAR РУС-2 and Redoubt

The first radars in the UK

In the UK, the research and development of the technology was led by Robert Watson-Watt, who showed the first successful demonstration of his device in 1935. In the second half of the 1930s, the first industrial devices began to appear, prototypes of radars were created for placement on airplanes, and in 1940 the construction of a network of long-range radar masts "Chain Home" or AMES (Air Ministry Experimental Station) Tipe 1, located along the coast of the British Isles, was fully completed. Later, the network was supplemented with a second locator for detecting low-flying aircraft Chain Home Low, aka AMES Tipe 2.

Robert Watson-Watt 1892 - 1973

The transmitting antenna consisted of fixed horizontal vibrators and reflectors mounted on a 115 m high mast. The receiving antennas, located on towers with a height of 80 m, consisted of two crossed vibrators to determine the azimuth and two vibrators located at different heights to determine the altitude of the aircraft by the angle of movement of the reflected signal.

Chain Home Tower in Great Baddow, Chelmsford

Chain Home Network Coverage Map

The first radars in Germany

At that time, in Germany, which already had a developed radio engineering industry at that time, under the leadership of Hans Holman (1899 - 1960), the Freya and Seetakt radars were developed and created in 1937. They are interesting because they used common-mode arrays of vibratory antennas as antenna devices, and magnetrons were also used in them, which made it possible to increase the power, frequency of radiation and increase the range of the installations.

Before the outbreak of World War II, Holman emigrated to the United States and greatly contributed to the development of American radars.

Also during the war (in 1942), for the first time in world history, radars with mirrored parabolic antennas, both stationary and portable, were built and put into service in Germany. And also for the first time in history, in the same year, a long-range radar was built using a phased array with electric scanning of the radiation pattern, called "Mammut" (Mammoth). It is worth noting that the parameters of these radars look good even in comparison with modern radars.

By the end of the war, Germany, in parallel with Great Britain, had completed the development of its aircraft airborne radars.

"Freya"

"Mammut"

The first radars in the USA

In the USA, the radar development was led by B. Trevor, P. Carter and R. Page. Since 1936, test samples have been built, including a shipboard radar called "RADAR". This turned out to be a very convenient name, and later it was decided to use it for all American radars, and in the future it spread to other countries, eventually becoming a separate word.

The first contract of the American military with industry was concluded in 1939, when, with the help of Hans Holman, the production of radars with common-mode vibratory antenna arrays was mastered, and the first serial military radar SCR-268 (Signal Corps Radio No. 268) was released. Over time, by 1941, all US military bases were equipped with extremely effective, by the standards of that time, SCR-270 and SCR-271 radars. Including the infamous pearl Harbor, then the radar operators successfully detected a group target and reported to the information center, but the officer on duty ignored this message, since no one actually expected an attack, and false alarms had already occurred earlier in the setup process.

SCR-268

Mobile version of SCR-270 and tower SCR-271

The first radars in Japan

In Japan, the development of radar technology lagged behind other countries by 3-4 years. Japanese military structures, partly due to their traditionalism and conservatism, for a long time showed almost no interest in technologies related to radio waves, especially radar, which is why, despite the technical potential and the developments of Japanese professor and researcher Hidetsugu Yagi, who invented wave channel antennas. There was even a situation when the Japanese captured the English radar, they did not even know that a Japanese invention, the Yagi antenna itself, was installed on it. This trend would have continued even longer if the "Japanese-German agreement on defense against communism" had not been signed.

In 1940, a delegation of Japanese Naval officers visited Germany, where they were shown samples of German and British radars and told some of the features of their work. The head of the delegation, Yojiro Ito, realizing how hopelessly Japan had lagged behind in the field of radar, immediately sent this information to his own, after which developments in this area began immediately, which were not particularly successful and the first working copy was created in 1941, a few days before Japan entered the war. Therefore, the first Japanese radars were based in principle on the locators of other countries, and their production was haphazard. For example, the tachi-1 and tachi-2 were created on the basis of the American SCR-268 radar and assembled in an amount of 25 pieces each, and the tachi-3 based on the captured English GL M-k-II and only 150 pieces were produced.

Tachi-1 and tachi-2

Tachi-3 transmitting antenna

Modern radars

After the war, the development of technology continued, the logical improvement was to increase the range. In 1946, Soviet radio scientist Nikolai Kabanov proposed the idea of detecting aircraft at a distance of up to 3,000 kilometers by reflecting probing rays from the ionosphere, for some time he was developing a ZGRLS (over-the-horizon radar station) as part of the Fan research project and in 1948 he was able to receive a signal for the first time after reflection from the earth. The installation located in Mytishchi worked and even allowed tracking the coast of Turkey, but it was not possible to achieve the declared range at that time, and some scientists considered that this was fundamentally impossible, because the Fan project was closed in 1950.

Nikolai Ivanovich Kabanov 1912 - 1984

Research in this area was also conducted in the United States under the leadership of William J. Thaler (1925 - 2005), within the framework of the TeePee project (from the Thaler Project), experimental systems MUSIC (Multiple Storage, Integration, and Correlation) and MADRE (Magnetic-Drum Radar Equipment) were created, which was able in 1961 to fix aircraft at a distance of up to 3,000 kilometers.

Meanwhile, the scientific research project "Duga-1" was conducted in the USSR, which was led by Efim Semyonovich Shtyren from 1958 to 1961 and which remained secret until the mid-1980s. As part of the project, at least 3 stations using headlights were built: "Duga-N" near Nikolaev, "Duga No. 1" in the Chernobyl area and the third facility was located in the village. A big cartel. At the moment, only one station has been preserved (Chernobyl 2),

The complex of radar antennas "Duga" in the city of Chernobyl 2

Nowadays, radar with headlights has become especially widely used, due to their high characteristics and the ability to detect low-flying targets, which has now become common, since modern air defenses essentially have no height limit at which missiles and aircraft can be shot down. In an active headlight, abbreviated as AFAR, the direction of radiation and the shape of the radiation pattern can also be adjusted by changing the distribution of currents or excitation fields on individual elements, although they consume more energy and have a higher cost.

Modern mobile radar with headlights

On-board radars

Also, after the war, the development of radars for placement on airplanes continued, the impetus for their development was the emergence of jet aviation and now aviation radars (airborne radars) are an integral part of both military and civil aviation. They are characterized by particularly high technical complexity and high cost, which is associated with somewhat contradictory requirements for technical characteristics, since such radars must have minimal weight and dimensions with high reliability in conditions of pressure and temperature fluctuations.

Modern on-boaed radar

Usually, radar is needed to simplify the piloting of aircraft, although nowadays the opposite situation also happens, when an aircraft is needed in order to raise the radar to a high altitude. As an example, such radar aircraft include the A-100 and Boeing E-3G.

A-100

Boeing E-3G