Modern warfare is swift and fleeting. Often the winner in a combat encounter is the one who is the first to be able to detect a potential threat and respond adequately to it. For more than seventy years, to search for the enemy on land, sea and in the air, a radar method has been used, based on the emission of radio waves and the registration of their reflections from various objects. Devices that send and receive such signals are called radar stations or radars.

The term "radar" is an English abbreviation (radio detection and ranging), which was put into circulation in 1941, but has long since become an independent word and entered most of the world's languages.

The invention of radar is, of course, a landmark event. The modern world is hard to imagine without radar stations. They are used in aviation, in maritime transportation, with the help of radar the weather is predicted, violators of traffic rules are identified, and the earth's surface is scanned. Radar systems (RLK) have found their application in the space industry and in navigation systems.

However, radars are most widely used in military affairs. It should be said that this technology was originally created for military needs and reached the stage of practical implementation just before the start of World War II. All the major countries participating in this conflict actively (and not without result) used radar stations for reconnaissance and detection of enemy ships and aircraft. It can be confidently asserted that the use of radars decided the outcome of several significant battles both in Europe and in the Pacific theater of operations.

Today, radars are used to solve an extremely wide range of military tasks, from tracking the launch of intercontinental ballistic missiles to artillery reconnaissance. Each aircraft, helicopter, warship has its own radar system. Radars are the backbone of the air defense system. The newest radar system with a phased array antenna will be installed on a promising Russian tank "Armata". In general, the variety of modern radars is amazing. These are completely different devices that differ in size, characteristics and purpose.

It can be said with confidence that today Russia is one of the recognized world leaders in the development and production of radars. However, before talking about the trends in the development of radar systems, a few words should be said about the principles of operation of radars, as well as the history of radar systems.

How Radar Works

Location is a method (or process) of determining the location of something. Accordingly, radar is a method of detecting an object or object in space using radio waves that are emitted and received by a device called a radar or radar.

The physical principle of operation of the primary or passive radar is quite simple: it transmits radio waves into space, which are reflected from surrounding objects and return to it in the form of reflected signals. Analyzing them, the radar is able to detect an object at a certain point in space, as well as show its main characteristics: speed, height, size. Any radar is a complex radio engineering device consisting of many components.

The structure of any radar includes three main elements: a signal transmitter, an antenna and a receiver. All radar stations can be divided into two large groups:

• impulse;
• continuous action.

The pulse radar transmitter emits electromagnetic waves for a short period of time (fractions of a second), the next signal is sent only after the first pulse returns and hits the receiver. The pulse repetition frequency is one of the most important characteristics of a radar. Low frequency radars send out several hundred pulses per minute.

The pulse radar antenna works for both reception and transmission. After the signal is emitted, the transmitter turns off for a while and the receiver turns on. After receiving it, the reverse process occurs.

Pulse radars have both disadvantages and advantages. They can determine the range of several targets at once, such a radar can easily do with one antenna, the indicators of such devices are simple. However, in this case, the signal emitted by such a radar should have a fairly high power. It can also be added that all modern tracking radars are made according to a pulsed scheme.

Pulse radar stations usually use magnetrons, or traveling wave tubes, as the signal source.

The radar antenna focuses the electromagnetic signal and directs it, picks up the reflected pulse and transmits it to the receiver. There are radars in which the reception and transmission of a signal are carried out by different antennas, and they can be located at a considerable distance from each other. The radar antenna is capable of emitting electromagnetic waves in a circle or working in a certain sector. The radar beam can be directed in a spiral or be shaped like a cone. If necessary, the radar can follow a moving target by constantly pointing the antenna at it with the help of special systems.

The functions of the receiver include processing the received information and transferring it to the screen, from which it is read by the operator.

In addition to pulse radars, there are also continuous-wave radars that constantly emit electromagnetic waves. Such radar stations use the Doppler effect in their work. It lies in the fact that the frequency of an electromagnetic wave reflected from an object that approaches the signal source will be higher than from a receding object. The frequency of the emitted pulse remains unchanged. Radars of this type do not fix stationary objects, their receiver picks up only waves with a frequency above or below the emitted one.

A typical Doppler radar is the radar used by traffic police to determine the speed of vehicles.

The main problem with continuous radars is the inability to use them to determine the distance to the object, but during their operation there is no interference from stationary objects between the radar and the target or behind it. In addition, Doppler radars are fairly simple devices that require low-power signals to operate. It should also be noted that modern radar stations with continuous radiation have the ability to determine the distance to the object. To do this, use the change in the frequency of the radar during operation.

One of the main problems in the operation of pulse radars is the interference that comes from stationary objects - as a rule, this is the earth's surface, mountains, hills. During the operation of airborne pulsed aircraft radars, all objects located below are “obscured” by the signal reflected from the earth's surface. If we talk about ground-based or shipborne radar systems, then for them this problem manifests itself in the detection of targets flying at low altitudes. To eliminate such interference, the same Doppler effect is used.

In addition to primary radars, there are so-called secondary radars that are used in aviation to identify aircraft. The composition of such radar systems, in addition to the transmitter, antenna and receiver, also includes an aircraft transponder. When irradiated with an electromagnetic signal, the transponder gives additional information about the altitude, route, aircraft number, and its nationality.

Also, radar stations can be divided by the length and frequency of the wave on which they operate. For example, to study the surface of the Earth, as well as to work at considerable distances, waves of 0.9-6 m (frequency 50-330 MHz) and 0.3-1 m (frequency 300-1000 MHz) are used. For air traffic control, a radar with a wavelength of 7.5-15 cm is used, and over-the-horizon radars of missile launch detection stations operate at waves with a wavelength of 10 to 100 meters.

History of radar

The idea of ​​radar arose almost immediately after the discovery of radio waves. In 1905, Christian Hülsmeyer, an employee of the German company Siemens, created a device that could detect large metal objects using radio waves. The inventor suggested installing it on ships so that they could avoid collisions in conditions of poor visibility. However, ship companies were not interested in the new device.

Experiments with radar were also carried out in Russia. As early as the end of the 19th century, the Russian scientist Popov discovered that metal objects prevent the propagation of radio waves.

In the early 1920s, American engineers Albert Taylor and Leo Young managed to detect a passing ship using radio waves. However, the state of the radio engineering industry of that time was such that it was difficult to create industrial models of radar stations.

The first radar stations that could be used to solve practical problems appeared in England around the mid-1930s. These devices were very large and could only be installed on land or on the deck of large ships. It was not until 1937 that a miniature radar prototype was created that could be installed on an aircraft. By the start of World War II, the British had an deployed chain of radar stations called Chain Home.

Engaged in a new promising direction in Germany. And, I must say, not without success. Already in 1935, the Commander-in-Chief of the German Navy, Raeder, was shown a working radar with a cathode-beam display. Later, production models of the radar were created on its basis: Seetakt for the naval forces and Freya for air defense. In 1940, the Würzburg radar fire control system began to enter the German army.

However, despite the obvious achievements of German scientists and engineers in the field of radar, the German army began to use radar later than the British. Hitler and the top of the Reich considered radars to be exclusively defensive weapons, which the victorious German army did not really need. It is for this reason that by the beginning of the Battle of Britain, the Germans had deployed only eight Freya radar stations, although in terms of their characteristics they were at least as good as their British counterparts. In general, it can be said that it was the successful use of radar that largely determined the outcome of the Battle of Britain and the subsequent confrontation between the Luftwaffe and the Allied Air Force in the skies of Europe.

Later, the Germans, based on the Würzburg system, created an air defense line, which was called the Kammhuber Line. Using special forces units, the Allies were able to unravel the secrets of the German radar, which made it possible to effectively jam them.

Despite the fact that the British entered the “radar” race later than the Americans and Germans, at the finish line they managed to overtake them and approach the beginning of World War II with the most advanced radar detection system for aircraft.

Already in September 1935, the British began to build a network of radar stations, which already included twenty radar stations before the war. It completely blocked the approach to the British Isles from the European coast. In the summer of 1940, British engineers created a resonant magnetron, which later became the basis of airborne radar stations installed on American and British aircraft.

Work in the field of military radar was also carried out in the Soviet Union. The first successful experiments on detecting aircraft using radar stations in the USSR were carried out as early as the mid-1930s. In 1939, the first RUS-1 radar was adopted by the Red Army, and in 1940 - RUS-2. Both of these stations were launched into mass production.

The Second World War clearly showed the high efficiency of the use of radar stations. Therefore, after its completion, the development of new radars became one of the priority areas for the development of military equipment. Over time, airborne radars were received by all military aircraft and ships without exception, radars became the basis for air defense systems.

During the Cold War, the United States and the USSR acquired a new destructive weapon - intercontinental ballistic missiles. Detecting the launch of these missiles became a matter of life and death. Soviet scientist Nikolai Kabanov proposed the idea of ​​using short radio waves to detect enemy aircraft at long distances (up to 3,000 km). It was quite simple: Kabanov found out that radio waves 10-100 meters long are capable of being reflected from the ionosphere, and irradiating targets on the earth's surface, returning the same way to the radar.

Later, based on this idea, radars for over-the-horizon detection of ballistic missile launches were developed. An example of such radars is Daryal, a radar station that for several decades was the basis of the Soviet missile launch warning system.

Currently, one of the most promising areas for the development of radar technology is the creation of a radar with a phased antenna array (PAR). Such radars have not one, but hundreds of radio wave emitters, which are controlled by a powerful computer. Radio waves emitted by different sources in the phased array can amplify each other if they are in phase, or, conversely, weaken.

The phased array radar signal can be given any desired shape, it can be moved in space without changing the position of the antenna itself, and work with different radiation frequencies. A phased array radar is much more reliable and sensitive than a conventional antenna radar. However, such radars also have disadvantages: the cooling of the radar with phased array is a big problem, in addition, they are difficult to manufacture and expensive.

New phased array radars are being installed on fifth-generation fighters. This technology is used in the US missile attack early warning system. The radar complex with PAR will be installed on the newest Russian tank "Armata". It should be noted that Russia is one of the world leaders in the development of PAR radars.

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Modern wars are distinguished by their swiftness and transience. Often the winners in combat encounters are those who were the first to detect potential threats and react accordingly. For eighty years now, radar methods have been used for reconnaissance and recognition of the enemy at sea and on land, as well as in airspace.

They are based on the emission of radio waves with the registration of their reflections from a wide variety of objects. Installations that send and receive such signals are modern radar stations or radars. The concept of "radar" comes from the English abbreviation - RADAR. It appeared in 1941 and has long been included in the languages ​​of the world.

The advent of radar was a landmark event. In the modern world, it is almost impossible to do without radar stations. Aviation, navigation, hydrometeorological center, traffic police, etc. cannot do without them. Moreover, the radar complex is widely used in space technologies and in navigation systems.

Radar in military service

Yet most of all, the military liked the radars. Moreover, these technologies were originally created for military use and were practically implemented before the Second World War. All major states actively used radar to detect enemy ships and aircraft. Moreover, their use decided the outcome of many battles.

To date, new radar stations are used in a very wide range of military tasks. This includes tracking intercontinental ballistic missiles and artillery reconnaissance. All planes, helicopters, warships have their own radar. Radars are generally the basis of air defense systems.

How Radars Work

Location is the definition of where something is. Thus, radar is the detection of objects or objects in space using radio waves that are emitted and received by a radar or radar. The principle of operation of primary or passive radars is based on the transmission into space of radio waves reflected from objects and returned to them in the form of reflected signals. After analyzing them, radars detect objects at certain points in space, their main characteristics in the form of speed, height and size. All radars are complex radio engineering devices made up of many elements.

Modern radar complex

Any radar consists of three main elements:

• signal transmitters;
• Antennas;
• Receivers.

Of all the radar stations, there is a special division into two large groups:

• Pulse;
• Continuous action.

Pulse radar transmitters emit electromagnetic waves for short periods of time (fractions of a second). The next signals are sent only when the first pulses come back and hit the receivers. The pulse repetition rates are also the most important characteristics. So low-frequency radars send more than one hundred pulses within a minute.

Pulse radar antennas work like transmitters and receivers. As soon as the signals are gone, the transmitters turn off for a while and the receivers turn on. Following their reception, reverse processes occur.

Pulse radars have their own advantages and disadvantages. They can determine the range of several targets at the same time. Such radars may have one antenna each, and their indicators are quite simple.

However, the emitted signals must be of high power. All modern tracking radars have a pulse circuit. Pulse radar stations usually use magnetrons or traveling wave tubes as signal sources.

Pulse radar systems

Radar antennas focus and direct electromagnetic signals, as well as pick up reflected pulses and transmit them to receivers. In some radars, signals can be received and transmitted using different antennas located at large distances from one another. Radar antennas can emit electromagnetic waves in a circle or operate in certain sectors.

Radar beams can be directed spirally or have cone shapes. If necessary, radars can track moving targets, and all the time direct antennas at them using special systems. The receivers process the received data and transfer it to the screens of the operators.

One of the main shortcomings in the operation of pulsed radars is interference coming from immovable objects, from the earth's surface, mountains, hills. Thus, airborne pulsed radars, in the course of their operation in aircraft, will receive shadows from signals reflected by the earth's surface. Ground-based or shipborne radar systems identify these problems in the process of detecting targets that fly at low altitudes. To eliminate such interference, the Doppler effect is used.

Continuous radar

Continuous radars operate by constantly emitting electromagnetic waves and use the Doppler effect. Its principle is that the frequencies of electromagnetic waves reflected from objects approaching signal sources will be higher than from receding objects. In this case, the frequencies of the emitted pulses remain unchanged. Such radars do not detect stationary objects; their receivers pick up only waves with frequencies above or below those emitted.

The main disadvantage of continuous action radars is their inability to determine distances to objects. However, during their operation, there is no interference from stationary objects between the radars and targets, or behind them. Also, Doppler radars have a relatively simple device, which will have enough signals with low power to function. In addition, modern continuous-wave radars have the ability to determine distances to objects. To do this, changes in the frequencies of the radars in the course of their action are applied.

It is also known about the so-called secondary radars used in aviation to identify aircraft. In such radar systems, there are also aircraft transponders. During the exposure of aircraft to electromagnetic signals, the transponders provide additional data, such as altitude, route, aircraft number, and nationality.

Varieties of radar stations

Radars can be separated by the length and frequency of the waves they operate on. In particular, when the earth's surface is being studied and when working at long distances, waves of 0.9-6 m and 0.3-1 m are used. In air traffic control, radars with a wavelength of 7.5-15 cm are used, and in over-the-horizon radars at stations for detecting missile launches, 10-100-meter waves are used.

From the history of the development of radar

The idea of ​​using radar arose after the discovery of radio waves. So, in 1905, an employee of Siemens, Christian Hülsmeyer, created a device that, using radio waves, could detect the presence of large metal objects. The inventor proposed to install such devices on ships in order to avoid collisions, for example, in fogs. However, no interest in the new device was expressed in the shipping companies.

Radar studies were also carried out on the territory of Russia. So, at the end of the 19th century, the Russian scientist Popov discovered that the presence of metal objects prevents the propagation of radio waves.

In the early twenties, American engineers Albert Taylor and Leo Young discovered a passing ship using radio waves. However, due to the fact that the radio engineering industry of that time was undeveloped, it was not possible to create radar stations on an industrial scale.

The production of the first radar stations, with the help of which practical problems would be solved, began in England in the 30s. This equipment was extremely bulky and could be installed either on the ground or on large ships. It was only in 1937 that the first miniature radar was created that could be installed on aircraft. As a result, before the Second World War, the British had an extensive network of radar stations called Chain Home.

Cold War Radars

During the Cold War, a new type of destructive weapon emerged in the United States and the Soviet Union. Of course, this was the appearance of intercontinental ballistic missiles. Timely detection of launches of such missiles was vital.

Soviet scientist Nikolai Kabanov proposed the idea of ​​using short radio waves to detect enemy aircraft at considerable distances (up to 3,000 km). Everything was simple enough. The scientist was able to find that 10-100-meter radio waves have a predisposition to reflection from the ionosphere.

Thus, when irradiating targets on the earth's surface, they also return back to the radars. Later, based on this idea, scientists were able to develop radars with over-the-horizon detection of ballistic missile launches. An example of such installations can be "Daryal" - a radar station. For decades, it was at the heart of Soviet missile launch warning systems.

To date, the most promising direction in the development of radar systems is considered to be the creation of radar stations with phased antenna arrays (PAR). Such devices have not one, but hundreds of radio wave emitters. All their functioning is controlled by powerful computers. The radio waves emitted by different sources in the HEADLIGHTS can be amplified one by one, or vice versa, when they are in phase or attenuated.

Phased array radar signals can be given any desired shape. They can move in space in the absence of changes in the positions of the antennas themselves, and also operate at different radiation frequencies. Phased array radars are considered more reliable and more sensitive than the same devices with conventional antennas.

However, such radars also have disadvantages. The biggest problems with PAR radars are their cooling systems. Moreover, such radar installations are extremely complex in the production process, as well as very expensive.

Radar complexes with PAR

What is known about the new phased array radars is that they are already being installed on fifth-generation fighters. Such technologies are used in American systems with early warning of missile attacks. Radar systems with phased array are supposed to be installed on the "Armata" - the latest Russian-made tanks. Many experts note that the Russian Federation is one of the world leaders successfully developing radar stations with phased array.

Radar station(radar) or radar(English) radar from Radio Detection and Ranging- radio detection and ranging) - a system for detecting air, sea and ground objects, as well as for determining their range and geometric parameters. It uses a method based on the emission of radio waves and the registration of their reflections from objects. The English term-acronym appeared in the city, later in its spelling capital letters were replaced by lowercase.

Story

On January 3, 1934, an experiment was successfully carried out in the USSR to detect an aircraft using a radar method. An aircraft flying at an altitude of 150 meters was detected at a distance of 600 meters from the radar installation. The experiment was organized by representatives of the Leningrad Institute of Electrical Engineering and the Central Radio Laboratory. In 1934, Marshal Tukhachevsky wrote in a letter to the government of the USSR: "Experiments in detecting aircraft using an electromagnetic beam confirmed the correctness of the underlying principle." The first experimental installation "Rapid" was tested in the same year, in 1936 the Soviet centimeter radar station "Storm" spotted the aircraft from a distance of 10 kilometers. In the United States, the first contract between the military and industry was concluded in 1939. In 1946, American specialists - Raymond and Hucherton, a former employee of the US Embassy in Moscow, wrote: "Soviet scientists successfully developed the theory of radar several years before the radar was invented in England."

Radar classification

By purpose, radar stations can be classified as follows:

• detection radar;
• control and tracking radar;
• Panoramic radars;
• side-looking radar;
• Meteorological radars.

According to the scope of application, military and civilian radars are distinguished.

By the nature of the carrier:

• Ground radars
• Marine radars
• Airborne radar

By type of action

• Primary or passive
• Secondary or active
• Combined

By waveband:

• Meter
• centimeter
• millimeter

The device and principle of operation of the Primary radar

Primary (passive) radar mainly serves to detect targets by illuminating them with an electromagnetic wave and then receiving reflections (echoes) of this wave from the target. Since the speed of electromagnetic waves is constant (the speed of light), it becomes possible to determine the distance to the target based on the measurement of the propagation time of the signal.

At the heart of the device of the radar station are three components: transmitter, antenna and receiver.

Transmitting device is a source of high power electromagnetic signal. It can be a powerful pulse generator. For centimeter-range pulse radars, it is usually a magnetron or a pulse generator operating according to the scheme: a master oscillator is a powerful amplifier that most often uses a traveling wave lamp as a generator, and for a meter-range radar, a triode lamp is often used. Depending on the design, the transmitter either operates in a pulsed mode, generating repetitive short powerful electromagnetic pulses, or emits a continuous electromagnetic signal.

Antenna performs receiver signal focusing and beamforming, as well as receiving the signal reflected from the target and transmitting this signal to the receiver. Depending on the implementation, the reception of the reflected signal can be carried out either by the same antenna, or by another, which can sometimes be located at a considerable distance from the transmitting device. If transmission and reception are combined in one antenna, these two actions are performed alternately, and so that a powerful signal leaking from the transmitting transmitter to the receiver does not blind the weak echo receiver, a special device is placed in front of the receiver, which closes the receiver input at the moment the probing signal is emitted.

receiving device performs amplification and processing of the received signal. In the simplest case, the resulting signal is applied to a ray tube (screen), which displays an image synchronized with the movement of the antenna.

Coherent radars

The coherent radar method is based on the selection and analysis of the phase difference between the sent and reflected signals, which occurs due to the Doppler effect, when the signal is reflected from a moving object. In this case, the transmitting device can operate both continuously and in a pulsed mode. The main advantage of this method is that it "allows observation of only moving objects, and this excludes interference from stationary objects located between the receiving equipment and the target or behind it."

Pulse radars

The principle of operation of the impulse radar

The principle of determining the distance to an object using pulsed radar

Modern tracking radars are built as impulse radars. Pulse radar only transmits for a very short time, a short pulse usually about a microsecond in duration, after which it listens for an echo as the pulse propagates.

Because the pulse travels away from the radar at a constant speed, the time elapsed from the moment the pulse was sent to the time the echo is received is a clear measure of the direct distance to the target. The next pulse can be sent only after some time, namely after the pulse comes back, it depends on the detection range of the radar (given by the transmitter power, antenna gain and receiver sensitivity). If the pulse had been sent earlier, then the echo of the previous pulse from a distant target could be confused with the echo of the second pulse from a close target.

The time interval between pulses is called pulse repetition interval, its reciprocal is an important parameter, which is called pulse repetition frequency(PPI) . Long range low frequency radars typically have a repetition interval of several hundred pulses per second (or Hertz [Hz]). The pulse repetition frequency is one of the hallmarks by which it is possible to remotely determine the radar model.

Elimination of passive interference

One of the main problems of pulse radars is getting rid of the signal reflected from stationary objects: the earth's surface, high hills, etc. If, for example, the aircraft is against the background of a high hill, the reflected signal from this hill will completely block the signal from the aircraft. For ground-based radars, this problem manifests itself when working with low-flying objects. For airborne pulse radars, it is expressed in the fact that the reflection from the earth's surface obscures all objects lying below the aircraft with the radar.

Interference elimination methods use, one way or another, the Doppler effect (the frequency of a wave reflected from an approaching object increases, from a departing object it decreases).

The simplest radar that can detect a target in interference is moving target radar(MPD) - pulsed radar that compares reflections from more than two or more pulse repetition intervals. Any target that appears to be moving relative to the radar produces a change in the signal parameter (stage in serial SDM), while the clutter remains unchanged. Interference is eliminated by subtracting reflections from two successive intervals. In practice, the elimination of interference can be carried out in special devices - through period compensators or algorithms in software.

FCRs operating at a constant pulse repetition rate have a fundamental weakness: they are blind to targets with specific circular velocities (which produce phase changes of exactly 360 degrees), and such targets are not displayed. The speed at which the target disappears for the radar depends on the operating frequency of the station and on the pulse repetition rate. Modern MDCs emit multiple pulses at different repetition rates - such that the invisible speeds at each pulse repetition rate are covered by other PRFs.

Another way to get rid of interference is implemented in pulse-doppler radar, which use significantly more complex processing than SDC radars.

An important property of pulse-Doppler radars is signal coherence. This means that the sent signals and reflections must have a certain phase dependence.

Pulse-Doppler radars are generally considered superior to MDS radars in detecting low-flying targets in multiple ground clutter, this is the technique of choice used in modern fighter aircraft for aerial interception/fire control, examples are AN/APG-63, 65, 66, 67 and 70 radars. In modern Doppler radar, most of the processing is done digitally by a separate processor using digital signal processors, usually using the high-performance Fast Fourier Transform algorithm to convert the digital reflection pattern data into something more manageable by other algorithms. Digital signal processors are very flexible and the algorithms used can usually be quickly replaced by others, replacing only the memory (ROM) chips, thus quickly counteracting enemy jamming techniques if necessary.

The device and principle of operation of the Secondary radar

The principle of operation of the secondary radar is somewhat different from the principle of the Primary radar. The device of the Secondary Radar Station is based on the components: transmitter, antenna, azimuth mark generators, receiver, signal processor, indicator and aircraft transponder with antenna.

Transmitter. Serves to emit interrogation pulses to the antenna at a frequency of 1030 MHz

Antenna. Serves for the emission and reception of the reflected signal. According to ICAO standards for secondary radar, the antenna transmits at a frequency of 1030 MHz, and receives at a frequency of 1090 MHz.

Azimuth Marker Generators. They are used to generate Azimuth Change Pulse or ACP and to generate Azimuth Reference Pulse or ARP. For one revolution of the radar antenna, 4096 small azimuth marks are generated (for old systems), or 16384 Small azimuth marks (for new systems), they are also called improved small azimuth marks (Improved Azimuth Change pulse or IACP), as well as one mark of the North. The north mark comes from the azimuth mark generator, with the antenna in such a position when it is directed to the North, and small azimuth marks serve to read the antenna turn angle.

Receiver. Used to receive pulses at a frequency of 1090 MHz

signal processor. Used to process received signals

Indicator Serves to indicate processed information

Aircraft transponder with antenna Serves to transmit a pulsed radio signal containing additional information back to the side of the radar upon receipt of a request radio signal.

Operating principle The principle of operation of the secondary radar is to use the energy of the aircraft transponder to determine the position of the Aircraft. The radar irradiates the surrounding area with interrogation pulses at a frequency of P1 and P3, as well as a P2 suppression pulse at a frequency of 1030 MHz. Transponder-equipped aircraft that are within the coverage area of ​​the interrogation beam when receiving interrogation pulses, if the condition P1,P3>P2 is in effect, respond to the requesting radar with a series of coded pulses at a frequency of 1090 MHz, which contain additional information such as side number, altitude, and so on. The response of the aircraft transponder depends on the radar interrogation mode, and the interrogation mode is determined by the distance between the interrogation pulses P1 and P3, for example, in mode A of the interrogation pulses (mode A), the distance between the interrogation pulses of the station P1 and P3 is 8 microseconds, and when such a request is received, the transponder of the aircraft encodes its board number in the response pulses. In interrogation mode C (mode C), the distance between the interrogation pulses of the station is 21 microseconds, and upon receipt of such an interrogation, the transponder of the aircraft encodes its height in the response pulses. The radar can also send a mixed mode interrogation, such as Mode A, Mode C, Mode A, Mode C. The azimuth of the aircraft is determined by the angle of rotation of the antenna, which in turn is determined by calculating the Small Azimuth marks. The range is determined by the delay of the incoming response. If the Aircraft does not lie in the coverage area of ​​the main beam, but lies in the coverage area of ​​the side lobes, or is behind the antenna, then the Aircraft responder, upon receiving a request from the radar, will receive at its input the condition that P1 pulses ,P3

Advantages of the secondary radar, higher accuracy, additional information about the Aircraft (Side number, Altitude), as well as low radiation compared to Primary radars.

Other pages

• (German) Technology Radar station
• Section on radar stations on the dxdt.ru blog (Russian)
• http://www.net-lib.info/11/4/537.php Konstantin Ryzhov - 100 great inventions. 1933 - Taylor, Jung and Hyland come up with the idea of ​​radar. 1935 Watson-Watt Early Warning CH Radar Station.

Literature and footnotes

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Synonyms:

See what "RLS" is in other dictionaries:

radar- Russian Logistics Service http://www.rls.ru/​ Radar radar communication Dictionaries: Dictionary of abbreviations and abbreviations of the army and special services. Comp. A. A. Shchelokov. M .: AST Publishing House LLC, Geleos Publishing House CJSC, 2003. 318 p., From ... Dictionary of abbreviations and abbreviations

The radar emits electromagnetic energy and detects echoes coming from reflected objects and also determines their characteristics. The purpose of the course project is to consider the all-round radar and calculate the tactical indicators of this radar: the maximum range, taking into account absorption; real resolution in range and azimuth; real accuracy of range and azimuth measurements. In the theoretical part, a functional diagram of a pulsed active airborne radar for air traffic control is given.

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Radar systems (RLS) are designed to detect and determine the current coordinates (range, speed, elevation and azimuth) of reflected objects.

The radar emits electromagnetic energy and detects echoes coming from reflected objects, and also determines their characteristics.

The purpose of the course project is to consider the all-round radar and calculate the tactical indicators of this radar: the maximum range, taking into account absorption; real resolution in range and azimuth; real accuracy of range and azimuth measurements.

The theoretical part presents a functional diagram of a pulsed active airborne radar for air traffic control. The parameters of the system and formulas for its calculation are also given.

In the calculation part, the following parameters were determined: the maximum range taking into account absorption, the real resolution in range and azimuth, the accuracy of measuring range and azimuth.

1. Theoretical part

1.1 Functional diagram of the radarall-round view

Radar - a field of radio engineering that provides radar observation of various objects, that is, their detection, measurement of coordinates and motion parameters, as well as the identification of some structural or physical properties by using radio waves reflected or re-radiated by objects or their own radio emission. The information obtained in the process of radar surveillance is called radar. Radio technical radar surveillance devices are called radar stations (RLS) or radars. The objects of radar observation themselves are called radar targets or simply targets. When using reflected radio waves, radar targets are any inhomogeneities in the electrical parameters of the medium (dielectric and magnetic permeability, conductivity) in which the primary wave propagates. This includes aircraft (airplanes, helicopters, meteorological probes, etc.), hydrometeors (rain, snow, hail, clouds, etc.), river and sea vessels, ground objects (buildings, cars, aircraft at airports, etc. ), all kinds of military facilities, etc. A special type of radar targets are astronomical objects.

The source of radar information is a radar signal. Depending on the methods of obtaining it, the following types of radar surveillance are distinguished.

1. Radar with passive response,based on the fact that the vibrations emitted by the radar - the probing signal - are reflected from the target and enter the radar receiver in the form of a reflected signal. This type of surveillance is sometimes also referred to as passive response active radar.

Radar with active response,called active radar with an active response, is characterized by the fact that the response signal is not reflected, but re-radiated with the help of a special transponder - a repeater. This significantly increases the range and contrast of radar observation.

Passive radar is based on the reception of the own radio emission of targets, mainly millimeter and centimeter ranges. If the probing signal in the two previous cases can be used as a reference, which provides the fundamental possibility of measuring the range and speed, then in this case there is no such possibility.

The radar system can be considered as a radar channel like radio communication channels or telemetry. The main components of the radar are the transmitter, receiver, antenna device, terminal device.

The main stages of radar surveillance aredetection, measurement, resolution and recognition.

Discovery The process of making a decision about the presence of goals with an acceptable probability of an erroneous decision is called.

Measurement allows you to estimate the coordinates of targets and the parameters of their movement with acceptable errors.

Permission consists in performing the tasks of detecting and measuring the coordinates of one target in the presence of others that are closely spaced in range, speed, etc.

Recognition makes it possible to establish some characteristic features of the target: whether it is point or group, moving or group, etc.

Radar information coming from the radar is broadcast over a radio channel or by cable to the control point. The process of tracking the radar for individual targets is automated and carried out with the help of a computer.

Aircraft navigation along the route is provided by the same radars that are used in ATC. They are used both to control the maintenance of a given route, and to determine the location during the flight.

To perform landing and its automation, along with radio beacon systems, landing radars are widely used, which provide tracking of the aircraft's deviation from the course and glide path planning.

In civil aviation, a number of airborne radar devices are also used. First of all, this includes airborne radar for detecting dangerous meteorological formations and obstacles. Usually it also serves to survey the earth in order to provide the possibility of autonomous navigation along the characteristic ground radar landmarks.

Radar systems (RLS) are designed to detect and determine the current coordinates (range, speed, elevation and azimuth) of reflected objects. The radar emits electromagnetic energy and detects echoes coming from reflected objects, and also determines their characteristics.

Consider the operation of a pulsed active radar for detecting air targets for air traffic control (ATC), the structure of which is shown in Figure 1. The view control device (antenna control) is used to view space (usually circular) with an antenna beam that is narrow in the horizontal plane and wide in the vertical.

In the radar under consideration, a pulsed radiation mode is used, therefore, at the end of the next probing radio pulse, the only antenna switches from the transmitter to the receiver and is used for reception until the next probing radio pulse is generated, after which the antenna is reconnected to the transmitter and so on.

This operation is performed by a transmit-receive switch (TPP). The trigger pulses that set the repetition period of the probing signals and synchronize the operation of all radar subsystems are generated by the synchronizer. The signal from the receiver after the analog-to-digital converter (ADC) goes to the information processing equipment - the signal processor, where the primary processing of information is performed, which consists in detecting the signal and changing the coordinates of the target. Target marks and trajectory traces are formed during the primary processing of information in the data processor.

The generated signals, together with information about the angular position of the antenna, are transmitted for further processing to the command post, as well as for control to the all-round visibility indicator (PPI). During autonomous operation of the radar, the IKO serves as the main element for monitoring the air situation. Such a radar usually processes information in digital form. For this, a device for converting a signal into a digital code (ADC) is provided.

Figure 1 Functional diagram of the all-round radar

1.2 Definitions and basic parameters of the system. Formulas for calculation

The main tactical characteristics of the radar

Maximum range

The maximum range is set by tactical requirements and depends on many technical characteristics of the radar, the conditions for the propagation of radio waves and the characteristics of targets, which are subject to random changes in real conditions of use of the stations. Therefore, the maximum range is a probabilistic characteristic.

The free-space range equation (i.e., without taking into account the influence of the ground and atmospheric absorption) for a point target establishes a relationship between all the main parameters of the radar.

where E izl - energy emitted in one pulse;

S a - effective antenna area;

S efo - effective reflective target area;

 - wavelength;

to r - distinguishability coefficient (the signal-to-noise energy ratio at the receiver input, which ensures the reception of signals with a given probability of correct detection W by and false alarm probability W lt );

E w - energy of the noises acting at reception.

Where R and - and pulse power;

 and , - pulse duration.

Where d ag - horizontal dimension of the antenna mirror;

dav - vertical dimension of the antenna mirror.

k p \u003d k r.t. ,

where k r.t. - theoretical coefficient of distinguishability.

k r.t. =,

where q0 - detection parameter;

N - the number of pulses received from the target.

where W lt - probability of false alarm;

W by - probability of correct detection.

where t region ,

F and - pulse frequency;

Qa0.5 - antenna beamwidth at the level of 0.5 in terms of power

where is the angular velocity of the antenna.

where T obz - review period.

where k \u003d 1.38  10 -23 J/deg - Boltzmann's constant;

k w - noise figure of the receiver;

T - receiver temperature in degrees Kelvin ( T = 300K).

The maximum range of the radar, taking into account the absorption of radio wave energy.

where  osl - attenuation factor;

D - attenuating layer width.

Minimum range of the radar

If the antenna system does not impose restrictions, then the minimum range of the radar is determined by the pulse duration and the recovery time of the antenna switch.

where c is the propagation speed of an electromagnetic wave in vacuum, c = 3∙10 8 ;

 and , - pulse duration;

τ in - antenna switch recovery time.

Range resolution of the radar

The real range resolution when using the all-round visibility indicator as an output device is determined by the formula

 (D) \u003d  (D) sweat +  (D) ind,

d de  (d) sweat - potential range resolution;

 (D ) ind - range resolution of the indicator.

For a signal in the form of an incoherent burst of rectangular pulses:

where c is the propagation speed of an electromagnetic wave in vacuum; c = 3∙10 8 ;

 and , - pulse duration;

 (D ) ind - the range resolution of the indicator is calculated by the formula

g de d sk - limit value of the range scale;

k e = 0.4 - screen usage factor,

Q f - quality of tube focusing.

Radar resolution in azimuth

The real resolution in azimuth is determined by the formula:

 ( az) \u003d  ( az) sweat +  ( az) ind,

where  ( az) sweat - potential resolution in azimuth when approximating the Gaussian radiation pattern;

 ( az) ind - resolution of the indicator in azimuth

 ( az) sweat \u003d 1.3  Q a 0.5,

 ( az ) ind = d n M f ,

where dn - diameter of the cathode-ray tube spot;

Mf - scale scale.

where r - removal of the mark from the center of the screen.

Accuracy of determination of coordinates by range and

The accuracy of determining the range depends on the accuracy of measuring the delay of the reflected signal, errors due to non-optimal signal processing, on the presence of unaccounted for signal delays in the transmission, reception and indication paths, on random ranging errors in indicator devices.

Accuracy is characterized by measurement error. The resulting root-mean-square error of the range measurement is determined by the formula:

where  (D) sweat - potential ranging error.

 (D ) distribution – error due to non-straight propagation;

 (D) app - hardware error.

where q0 - double signal-to-noise ratio.

Azimuth coordinate accuracy

Systematic errors in azimuth measurements can occur due to inaccurate orientation of the radar antenna system and due to a mismatch between the position of the antenna and the electrical scale of the azimuth.

Random errors in measuring the target azimuth are caused by the instability of the antenna rotation system, the instability of the schemes for generating azimuth marks, as well as reading errors.

The resulting root mean square error of the azimuth measurement is given by:

Initial data (option 5)

1. Wave length  , [cm] …............................................. ........................... .... 6
2. Pulse power R and , [kW] ............................................... .............. 600
3. Pulse duration and , [µs] ............................................... ........... 2,2
4. Pulse frequency F and , [Hz] ............................................... ...... 700
5. Horizontal dimension of the antenna mirror d ar [m] ............................ 7
6. Vertical dimension of the antenna mirror dav , [m] ................................... 2.5
7. Review period T review , [With] .............................................. .............................. 25
8. Receiver noise figure k w ................................................. ....... 5
9. Probability of correct detection W by ............................. .......... 0,8
10. False alarm probability W lt.. ................................................ ....... 10 -5
11. Around view indicator screen diameter d e , [mm] .................... 400
12. Effective reflective target area S efo, [m 2 ] …...................... 30
13. Focus quality Q f ............................................................... ...... 400
14. Range scale limit D shk1 , [km] ...................... 50 D shk2 , [km] .......... 400
15. Distance measuring marksD , [km] ........................................ 15
16. Azimuth measurement marks , [deg] .............................................. 4

2. Calculation of tactical indicators of the all-round radar

2.1 Calculation of the maximum range with absorption

First, the maximum range of the radar is calculated without taking into account the attenuation of the energy of radio waves during propagation. The calculation is carried out according to the formula:

(1)

Let's calculate and set the values ​​included in this expression:

E izl \u003d P and  and \u003d 600  10 3  2.2  10 -6 \u003d 1.32 [J]

S a \u003d d ag d av \u003d  7  2.5 \u003d 8.75 [m 2]

k p \u003d k r.t.

k r.t. =

101,2

0.51 [deg]

14.4 [deg/s]

Substituting the obtained values, we will have:

t region = 0.036 [s], N = 25 pulses and k r.t. = 2.02.

Let = 10, then k P =20.

E w - the energy of the noise acting during reception:

E w \u003d kk w T \u003d 1.38  10 -23  5  300 \u003d 2.07  10 -20 [J]

Substituting all the obtained values ​​into (1), we find 634.38 [km]

Now let's determine the maximum range of the radar, taking into account the absorption of radio wave energy:

(2)

Value  osl find from the charts. For \u003d 6 cm  osl taken equal to 0.01 dB/km. Assume that attenuation occurs over the entire range. Under this condition, formula (2) takes the form of a transcendental equation

(3)

Equation (3) will be solved by a graph-analytical method. For osl = 0.01 dB/km and D max = 634.38 km we calculate D max. osl = 305.9 km.

Conclusion: It can be seen from the calculations that the maximum range of the radar, taking into account the attenuation of the energy of radio waves during propagation, is equal to D max.os l = 305.9 [km].

2.2 Calculation of real range and azimuth resolution

The real range resolution when using the all-round visibility indicator as an output device is determined by the formula:

 (D) =  (D) sweat +  (D) ind

For a signal in the form of an incoherent burst of rectangular pulses

0.33 [km]

for D sh1 =50 [km],  (D) ind1 =0.31 [km]

for D shk2 =400 [km],  (D) ind2 =2.50 [km]

Real range resolution:

for D sc1 = 50 km  (D) 1 =  (D) sweat +  (D) ind1 = 0.33+0.31=0.64 [km]

for D w2 =400 km

The real resolution in azimuth is calculated by the formula:

 ( az) \u003d  ( az) sweat +  ( az) ind

 ( az) sweat \u003d 1.3  Q a 0.5 \u003d 0.663 [deg]

 ( az) ind = d n M f

Taking r = k e d e / 2 (mark on the edge of the screen), we get

0.717 [deg]

 ( az)=0.663+0.717=1.38 [deg]

Conclusion: The real range resolution is equal to:

for D wk1 = 0.64 [km], for D wk2 = 2.83 [km].

Real resolution in azimuth:

 ( az)=1.38 [deg].

2.3 Calculation of the actual accuracy of range and azimuth measurements

Accuracy is characterized by measurement error. The resulting root-mean-square error of the range measurement is calculated by the formula:

40,86

 (D ) sweat = [km]

Error due to non-straight propagation (D ) distribution we neglect. Hardware bugs (D ) app are reduced to reading errors on the indicator scale (D ) ind . We accept the method of counting by electronic labels (scale rings) on the screen of the circular view indicator.

 (D ) ind = 0.1  D =1.5 [km] , where  D - price division of the scale.

 (D ) = = 5 [km]

The resulting root-mean-square error of the azimuth measurement is defined similarly:

0,065

 ( az) ind \u003d 0.1   \u003d 0.4

Conclusion: Having calculated the resulting root mean square error of the range measurement, we obtain (D)  ( az) \u003d 0.4 [deg].

Conclusion

In this course work, the calculation of the parameters of a pulsed active radar (maximum range, taking into account absorption, real resolution in range and azimuth, accuracy of measuring range and azimuth) detection of air targets for air traffic control is carried out.

During the calculations, the following data were obtained:

1. The maximum range of the radar, taking into account the attenuation of the energy of radio waves during propagation, is equal to D max.sl = 305.9 [km];

2. The real range resolution is:

for D shk1 = 0.64 [km];

for D shk2 = 2.83 [km].

Real resolution in azimuth: ( az)=1.38 [deg].

3. The resulting root-mean-square error of the range measurement is obtained(D) =1.5 [km]. RMS error of azimuth measurement ( az) \u003d 0.4 [deg].

The advantages of pulse radars include the simplicity of measuring distances to targets and their range resolution, especially when there are many targets in the field of view, as well as the almost complete time decoupling between received and emitted oscillations. The latter circumstance makes it possible to use the same antenna for both transmission and reception.

The disadvantage of pulse radars is the need to use a large peak power of the emitted oscillations, as well as the impossibility of measuring short ranges - a large dead zone.

Radars are used to solve a wide range of tasks: from ensuring a soft landing of spacecraft on the surface of planets to measuring the speed of a person, from controlling weapons in anti-missile and anti-aircraft defense systems to personal protection.

Bibliography

1. Vasin V.V. Operating range of radio engineering measuring systems. Methodical development. - M.: MIEM 1977.
2. Vasin V.V. Resolution and accuracy of measurements in radio engineering measuring systems. Methodical development. - M.: MIEM 1977.
3. Vasin V.V. Methods for measuring the coordinates and radial velocity of objects in radio engineering measuring systems. Lecture notes. - M.: MIEM 1975.

4. Bakulev P.A. Radar systems. Textbook for universities. - M .: "Radio-

Technique» 2004

5. Radio engineering systems: Textbook for universities / Yu. M. Kazarinov [and others]; Ed. Yu. M. Kazarinova. — M.: Academy, 2008. — 590 p.:

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Let's start at the beginning - what is radar and why is it needed? First of all, I would like to note that radar is a certain branch of radio engineering, which helps in determining the various characteristics of surrounding objects. The action of radar is directed to the supply of radio waves by an object to the device.

Radar, radar station is a certain combination of various devices and devices that allow you to monitor objects. The radio waves fed by the radar can detect the target under investigation and make a detailed analysis of it. Radio waves are refracted and, as it were, "draw" the image of the object. Radar stations can operate in all weather conditions and perfectly detect any objects on the ground, in the air or in the water.

Principles of operation of the radar

The action system is simple. Radio waves from the station are sent to objects, when they meet with them, the waves are refracted and reflected back to the radar. This is called radio echo. To detect this phenomenon, radio transmitters and radio receivers are installed in the station, which have high sensitivity. Previously, a couple of years ago, radar stations required huge costs. But not right now. It takes very little time for the correct operation of devices and the definition of objects.

All radar operations are based not only on the reflection of waves, but also on their dispersion.

Where can radar be used?

The scope of radar systems is quite wide.

• The first branch will be the military. Used to identify ground, water and air targets. Radars perform control and survey of the territory.
• Agriculture and forestry. With the help of such stations, specialists conduct research to study the soil and vegetation, as well as to detect various kinds of fires.
• Meteorology. Studying the state of the atmosphere and making forecasts based on the data obtained.
• Astronomy. Scientists use radar stations to study distant objects, pulsars and galaxies.

Radar in the automotive industry

Since 2017, developments have been underway at the MAI, which are aimed at creating a small-sized radar station for unmanned vehicles. Such small on-board vehicles could be installed in every car in the near future. In 2018, non-standard radars for unmanned aerial vehicles are already being tested. It is planned that such devices will be able to detect terrestrial objects at a distance of up to 60 kilometers, sea ones - up to 100 km.

It is worth recalling that in 2017 a small-sized airborne dual-band radar was also introduced. The unique device was designed to detect various kinds of objects and objects under any conditions.