Radar
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, subsequently in its spelling, capital letters were replaced by lowercase ones.
History
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 experts - 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.
The device of a radar station is based on 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 reflected signal can be received either by the same antenna or by a different one, which can sometimes be located at a considerable distance from the transmitter. 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 that 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.
Since 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. 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(CHPI) . 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 display 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 contains Additional Information type Bead number, Height 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. The rules of the road set speed limits on roads, for violating traffic rules, a driver may be fined or administratively punished (for example, deprivation of a driver's license). Car drivers, wishing to be informed about the work of the traffic police and / or in an effort to avoid punishment for intentional or unintentional traffic violations, install a radar detector on their cars. The radar detector is a passive device that detects police radar exposure and alerts the driver (exposure warning system). 1
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5 The simplest radar detectors and radar detectors are installed behind the windshield, on the interior rear-view mirror or in the car, connected to the on-board network (12 volts) through the cigarette lighter. More complex non-removable models for installation require the involvement of specialists. These devices are classified: (Instruments with a 360° response width can detect speed-monitoring radars at an angle to the direction of travel and on receding vehicles.) Radar detectors respond to interference generated by power lines, electric transport (tram, trolleybus, electric locomotives), so protection against false alarms is built into many models. The "radar jamming" design feature, or distorting the intruder's speed determined by the police radar, which actually makes it a "radar suppressor" is prohibited in all countries. In addition, some radar detectors can detect laser speed meters (lidars) as well as VG-2 systems (devices that detect radar detectors). In 2010-2012, the STRELKA-ST complex of video recording of offenses, popular with the Russian traffic police, was not detected by most radar detectors. In 2012, there were only a few models on sale (such functionality was announced for all NEOLINE models, some models of Cobra, Belltronics, Inspector). The use of radar detectors and radar detectors is regulated by law. For example, in Finland, these devices are prohibited, and the presence of an empty mount behind the windshield or in the passenger compartment attracts serious attention from the Finnish border guards. In some states and federal associations, local laws prohibit the use of laser/radar detectors. Before using the device, make sure that its use is permitted in your area. Throughout the territory of the Russian Federation, Ukraine and Belarus, the use of radar detectors is not prohibited. The presence of a radar detector in a car sometimes avoids unpleasant contacts with traffic inspectors and can positively influence the self-discipline of drivers, thereby increasing traffic safety. Traffic police inspectors, knowing that drivers often carry a radar detector in their car, use a different tactic of "hunting" traffic offenders. The policeman hides in an "ambush" and turns on his radar only for a very short time, "in the forehead" of an approaching car. The violating driver has no chance to slow down in advance in order to avoid punishment. But the driver can stop (the range of the radar is 300 meters) and stand for 10 minutes: after this interval, the readings of the device are automatically reset to zero. Also, a traffic police officer is unlikely to be able to prove that it is your speed on the device. We can say that this method of avoiding punishment is not effective. Recently, all traffic police radars must be equipped with photo or video recording devices, and therefore, no matter how much you stand, waiting for the radar to reset, nothing will come of it. Your photo or even video will be on the computer in the police car. Radar detectors, with the exception of models with a built-in GPS receiver, are ineffective against complexes that measure the time a car travels a certain distance, since this technology does not require the use of radio emission in the direction of a moving car. On May 7, 2009, information appeared on the official website of Britney Spears that the fourth single from the Circus album would be Radar, but already fully, not in the form of a promo. The song is rhythmically and lyrically similar to Britney Spears' Grammy-winning single Toxic. Both songs are full of electropop, synthpop and dance music tie-ins. Initially, for the planned release of the video in summer 2008, Britney Spears' manager Larry Rudolph stated that the music video for the song would be filmed in London. According to him, the plot will be as follows: "Britney and her friends will drive around London to find the guy they met at the club, but every time it will not be him." He also confirmed that Spears would co-direct the video. The premiere of the new music video for the song "Radar" was scheduled for June 24, but it was later officially confirmed that there would be no video for the song "Radar" as a single from the Blackout album. In May, Britney Spears' official website released information that the music video would be filmed in London in early June, where Britney would arrive to play 8 concerts at the O2 Arena. However, later the decision of the singer's managers changed, and the shooting was carried out at the Bacara Resort & Spa hotel, which is located north of Santa Barbara in the USA. Due to high levels of internet sales, "Radar" briefly appeared on several Billboard charts when Blackout began selling. On August 22, Radar entered the Billboard Hot 100 at number 90. In Russia, the single entered the Hot 40. Tags: Radars, radar device, the principle of operation of the radar, examples of the use of radars Radar is a device for detecting and locating objects in space by radio waves reflected from them; radar. The name of this radar device "radar" (Radar) comes from the abbreviation of its full name in English - Radio Detection And Ranging (radio detection and ranging). The principle by which the radar works can be described as follows: very similar to the principle of reflecting a sound wave. If you shout in the direction of a reflective object (such as a mountain gorge or a cave), you will hear an echo. If you know the speed of sound in air, you can then estimate the distance and the general direction and direction of the object. The time it takes for the echo to return can be roughly converted to distance if you know the speed of sound. The radar uses electromagnetic pulses. High frequency energy is measured by the radar and reflected from the observed object. Some small part of this reflected energy is returned back to the radar. This reflected energy is called an ECHO, just like in sound terminology. The radar uses this echo to determine the direction and distance to the reflecting object. As follows from this definition, radars are used to detect the presence of a target (object of detection) and determine its position in space. The abbreviation also implies the fact that the quantity measured is usually the distance to the object. On fig. 1. shows a simplified principle of operation of the simplest radar. The radar antenna irradiates the target with a microwave signal, which is then reflected from the target and "captured" by the receiving device. The electrical signal picked up by a radar receiving antenna is called an "echo" or "response". The radar signal is generated by a powerful transmitter and received by a special highly sensitive receiver. The operation algorithm of the simplest radar can be described as follows: All targets produce the so-called diffuse reflection, i.e. the signal is usually reflected in a wide range of directions. This reflected signal is also called "scatter" or backscatter, which is the term given to reflections of the signal in the opposite direction of the incident beam. Radar signals can be displayed on both the traditional Plane Position Indicator (PPI) and more modern (LCD, plasma, etc.) radar display systems. The PPI screen has a rotating radar vector at the origin that represents the direction of the antenna (azimuth of the targets). It usually depicts a picture of the area under study in the form of a map of the area covered by the radar beam. Obviously, most of the functions of the simplest radar are time dependent. Time synchronization between the radar transmitter and receiver is required for distance measurements. Radar systems emit each pulse during the transmission time (or pulse duration τ), wait for echoes to return during the "listening" or rest time, and then emit the next pulse, as shown in Fig. 2. The so-called synchronizer coordinates in time the synchronization process for determining the distance to the target and provides synchronization signals for the radar. It simultaneously sends signals to the transmitter, which sends the next new pulse, and to the indicator and other associated control circuits. The time between the start of one pulse and the start of the next pulse is called the period or pulse interval (PRT) and PRT = 1/PRF. Here, the pulse repetition frequency (PRF) of a simple radar system is the number of pulses that are transmitted per second. The frequency of pulse transmission significantly affects the maximum distance that can be displayed, which we will show below. The distance to a stationary or moving target (object) is determined from the transit time of the high-frequency transmitted signal and the propagation velocity (c0). The actual distance of the target from the radar is usually referred to as "slant range" - it is some line in the field of view between the radar and the object being illuminated, while the distance "on the ground" is the horizontal distance between the emitter and its target and its calculations require knowledge of the height of the target. As the waves travel to and from the target, the physical round-trip time of the radar beam is halved to give the time it takes for the wave to reach that target. Therefore, the following formula is usually used for calculations: Where R– slant range; t delay– the time required for the signal to travel to the target and back; from 0 is the speed of light (approximately 3 × 10 8 m/s). If the corresponding transit time ( t delay) is known, then the distance R between target and radar can be easily calculated using this expression. One practical problem in determining distance accuracy is how to unambiguously determine the distance to a target if the target returns a strong echo. This problem arises because pulsed radars typically transmit a train of pulses. The radar receiver measures the time between the rising edges of the last transmitted pulse and the echo pulse. In practice, it often happens that an echo will be received from the target at a considerable (large) distance after the transmission of the second transmission pulse. In this case, the radar will determine the "wrong" time interval and, as a result, the wrong distance. The measurement process assumes that the pulse is associated with the second transmitted pulse and shows a significantly smaller distance to the target compared to the actual distance. This is called "distance ambiguity" and occurs when there are large targets at distances longer than the pulse repetition time. The pulse repetition time determines the maximum "single digit" distance. To increase the value of the "one-digit" distance, it is necessary to increase the PRT (which means - to reduce the PRF). Echoes occurring after the receive time may be detected: – either at the transmit time, where they are not taken into account because the radar is not ready to receive at that time, – or at the next receive time, when they can lead to an error measurements. The area of unambiguous determination of the range of the radar can be determined using the formula: R unamb = RPT - τ ∙ c 0 2 The numerical value of the radar pulse repetition period (PRT) used is extremely important in determining the maximum distance, as the return time from the target, which exceeds the PRT of the radar system, manifests itself at incorrect positions (distances) on the radar screen. Reflections that appear at these "wrong" distances are considered as secondary echoes in time. In addition to the problem of the zone for unambiguously determining the range of distant targets (objects), there is also the problem of detecting objects at a minimum distance from the radar. It is known that when the leading edge of the echo pulse falls inside the transmit pulse, it is impossible to accurately determine the time of the "circular" passage. Minimum detectable distance ( Rmin) depends on the momentum of the transmitters at τ
and multiplexer recovery time t recovery in the following way: Runamb = τ - t recovery ∙ c 0 2 Since the radar receiver does not receive a signal until the end of the transmission pulse, it is necessary to disconnect it from the transmitter during transmission to avoid damage. In this case, the "echo" pulse comes from a very close target. Note that targets at a pulse-width equivalent distance from the radar are not detected. For example, a typical value for a pulse width of 1 µs for radar typically corresponds to a minimum detectable distance of 150 m, which is generally acceptable. However, "long" pulse radars have the disadvantage of a minimum distance, in particular pulse compression radars, which can use pulse durations in the order of tens or even hundreds of microseconds. Typical pulse duration τ is typically: – air defense radar: up to 800 µs (minimum distance 120 km); – civil airport air surveillance radar 1.5 µs (minimum distance 250 m); – airborne radar for detecting the movement of an object on the surface: 100 ns (minimum distance 25 m). Determining the direction of movement of the target (object) is another important function of the radar. Radar specialists often use the term **azimuth**, the direction to the target, which is determined by the directivity of the radar antenna. Directivity, sometimes referred to as "direction gain", is the ability of an antenna to concentrate transmitted energy in one particular direction. Accordingly, such an antenna with high directivity is called a directional antenna. By measuring the direction in which the antenna is pointing when receiving an echo, the coordinates of the target can be determined. The accuracy of the angle measurements is usually determined by the directivity, which is a certain function of the geometric size of the antenna. The “true” bearing of a radar target is the angle between true north and some notional line indicating the direction to the target. This angle is usually measured in the horizontal plane and clockwise from north. The azimuth angle to the radar target can also be measured clockwise from the center line of the radar carrier ship or aircraft and is referred to in this case as relative azimuth. In particular, fast and accurate transmission of information in azimuth between the radar turntable with an antenna mounted on it and information screens is of great practical importance for various servo systems of modern electronic equipment. These servo systems are used in older classical radar antennas and ballistic missile launchers and operate with instruments such as rotary torque sensors and rotary torque receivers. With each rotation of the antenna, the encoder sends out many pulses, which are then counted in the indicators. Some radars operate without (or with partial) mechanical movement. Radars of the first group use electronic phase scanning in azimuth and/or elevation (phased array antennas). The elevation angle is the angle between the horizontal plane and the line of sight, measured in the vertical plane. The elevation angle is usually described using the letter ε. The elevation angle is always positive above the horizon (elevation angle 0), and negative below the horizon (Figure 4.). A very important parameter for radar users is the height of the target above the ground (altitude), which is usually denoted by the letter H. The actual distance above sea level is considered the true altitude (Fig. 5.a). Altitude can be calculated using distance R and elevation angle ε as shown in fig. 5.b., where: However, in practice, as is known, the propagation of electromagnetic waves is also subject to the effect of refraction (the transmitted radar beam is not a straight line of the side of this triangle, it is bent), and the amount of deviation from a straight line depends on the following main factors: – transmitted wavelength; – barometric pressure of the atmosphere; – air temperature and – atmospheric humidity. Target accuracy is the degree of agreement between the estimated and actually measured position and/or speed of a target at a given point in time and its actual position (or speed). The accuracy of radio navigation performance is usually represented as a given statistical measure of "system error". It should be said that the specified value of the required accuracy represents the uncertainty of the recorded value relative to the true value and actually shows the interval in which the true value lies at the specified probability. A generally recommended level of this probability is 9–10%, which corresponds to about two standard deviations of the mean for a normal Gaussian distribution of the variable being measured. Any residual offset must be small compared to the stated accuracy requirement. The true value is that value which, under operating conditions, accurately characterizes the variable to be measured or observed over the required characteristic time interval, area and/or volume. Accuracy should not "conflict" with another important parameter - the resolution of the radar. Usually this radar parameter is a known value and is given in its specification. In fact, this is a characteristic of the ability of the antenna to focus the outgoing energy in a directional beam. Its numerical value is determined by a very simple relation: G = maximum radiation intensity average radiation intensity This parameter (antenna gain) describes the degree to which the antenna concentrates electromagnetic energy in a narrow angled beam. Two parameters related to antenna gain are the direction gain of the antenna and directivity. Antenna gain serves as a measure of performance relative to an isotropic source with an isotropic antenna directivity of 1. The power received from a given target is directly related to the square of the antenna gain when that antenna is used for both transmit and receive. This parameter characterizes the antenna gain - the coefficient of increase in the transmitted power in one desired direction. It can be noted that in this respect, the reference is an "isotropic" antenna, which transmits signal power equally in any arbitrary direction (Fig. 6). For example, if a focused beam has 50 times the power of an omnidirectional antenna with the same transmitter power, then the directional antenna has a gain of 50 (17 decibels). As noted above, usually in the simplest radars, the same antenna is used during transmission and reception. In the case of transmission, all the energy will be processed by the antenna. In the case of reception, the antenna has the same gain, but the antenna receives only a portion of the incoming energy. The "aperture" parameter of an antenna generally describes how well that antenna can receive power from an incoming electromagnetic wave. When using an antenna as a receiving signal, the aperture of the antenna can, for ease of understanding, be represented as the area of a circle built perpendicular to the incoming radiation, when all the radiation passing within the circle is output by the antenna to the matched load. Thus, incoming power density (W/m2) × aperture (m2) = incoming power from the antenna (W). Obviously, the antenna gain is directly proportional to the aperture. An isotropic antenna usually has an aperture of λ2/4π. An antenna with gain G has an aperture of Gλ2/4π. The dimensions of the antenna being designed depend on its required gain G and/or the wavelength used λ as an expression of the frequency of the radar transmitter. The higher the frequency, the smaller the antenna (or higher gain for equal sizes). Large "dish-shaped" radar antennas have an aperture almost equal to its physical area and gain typically between 32 and 40 dB. Changing the quality of the antenna (irregularity of the antenna, deformations, or the usual ice formed on its surface) has a very large effect on the gain. The minimum discernible echo is defined as the strength of the wanted echo at the receiving antenna that produces a discernible target mark on the screen. The minimum distinguishable signal at the input of the receiver provides the maximum detection distance for the radar. For each receiver, there is a certain amount of receive power at which the receiver can operate at all. This lowest operating received power is often referred to as MDS (Minimum Distinguishable Signal). Typical MDS values for a radar range from 104 to 113 dB. The numerical values of the value of the maximum target detection range can be determined from the expression: R max = P tx ∙ G 2 ∙ λ 2 ∙ σ t 4π 3 ∙ P MDS ∙ L S 4 The term "noise" is also widely used by developers and users of radar technology. The numerical value of MDS depends primarily on the signal-to-noise ratio, defined as the ratio of the useful signal energy to the noise energy. All radars, because they are all-electronic equipment, must operate reliably in the presence of a certain level of noise. The main source of noise is called thermal noise, and it is caused by the thermal motion of electrons. In general, all types of noise can be divided into two large groups: external atmospheric or cosmic noise and internal (receiver noise - generated internally in the radar receiver). The overall (integral) sensitivity of the receiver largely depends on the level of inherent noise of the radar receiver. A low noise receiver is usually designed using special design and components that are located at the very beginning of the path. Designing a receiver with very low noise performance is achieved by minimizing the noise figure in the very first block of the receiver. This component is typically characterized by low noise performance with high gain. For this reason, it is commonly referred to as a "Low Noise Preamplifier" (LNA). A false alarm is “an erroneous decision to detect a target by a radar, caused by noise or other interfering signals that exceed the detection threshold.” Simply put, this is an indication of the presence of a target by a radar when there is no real target. False signal intensity (FAR) is calculated using the following formula: FAR = number of decoys number of range cells Therefore, another parameter is used - the probability of target detection, which is defined as follows: P D = target detection all possible target marks ∙ 100% Depending on the function performed, radar devices (RLD) are classified as follows (Fig. 7) . Two large groups of radars can be singled out at once, differing in the type (kind) of the final information display device used. These are RLC with imaging and RLC without imaging. RLC with imaging forms a picture of the observed object or area. They are commonly used to map the earth's surface, other planets, asteroids, other celestial bodies, and to categorize targets for military systems. Non-imaging radars usually measure only in a linear one-dimensional representation of the image. Typical representatives of a non-imaging radar system are speed meters and radar altimeters. They are also called reflection meters because they measure the reflection properties of the object or area being observed. Examples of non-imaging secondary radars are car anti-theft systems, room protection systems, etc. All varieties of radars in foreign literature are divided into two large groups "Primary Radars" (primary radars) and "Secondary Radars" (secondary radars). Consider their differences, features of organization and application, using the terminology of the main source used below. The primary radar itself generates and transmits high-frequency signals that are reflected from targets. The resulting echoes are received and evaluated. Unlike the secondary radar, the primary radar emits and receives its own transmitted signal again as an echo. Sometimes the primary radar is equipped with an additional interrogator provided to the secondary radars to combine the advantages of both systems. In turn, Primary Radars are divided into two large groups - impulse (Pulses Radars) and wave (Continuous Wave). Pulse radar generates and transmits a high-frequency, high-power pulse signal. This pulse signal is followed by a longer time interval during which an echo can be received before the next signal is sent. As a result of processing, it is possible to determine the direction, distance and sometimes, if necessary, the height or height above sea level of the target based on the fixed position of the antenna and the propagation time of the pulse signal. These classic radars transmit very short pulses (for good range resolution) with extremely high pulse power (for maximum target recognition distance). In turn, all impulse radars can also be divided into two large groups. The first of these is pulsed radar using the pulse compression method. These radars transmit a relatively weak pulse with a long duration. Modulates the transmitted signal to obtain distance resolution also within the transmitted pulse using a pulse compression technique. Further, monostatic and bistatic radars are distinguished, representing the second group. The former are deployed in the same place, the transmitter and receiver are located together and the radar basically uses the same antenna for receiving and transmitting. Bistatic radars consist of separate receiver and transmitter locations (at a considerable distance). The so-called secondary radar is characterized in that the object using it, such as an aircraft, must have its own transponder (transmitting transponder) on board and this transponder responds to the request by transmitting a coded recall signal. This response may contain significantly more information than the primary radar can receive (eg altitude, identification code, or also any technical problems on board such as loss of radio communications). Continuous wave radars (CW radars) transmit a continuous high frequency signal. An echo signal is also received and processed continuously. The transmitted signal of this radar is constant in amplitude and frequency. This type of radar usually specializes in measuring the speed of various objects. For example, this equipment is used for speed meters. A CW radar transmitting unmodulated power can measure speed using the Doppler effect, but it cannot measure the distance to an object. CW radars have the main disadvantage that they cannot measure distance. To eliminate this problem, the frequency shift method can be used. The whole variety of radars can be divided into types based on their areas of use. Air defense radars can detect air targets and determine their position, course and speed over a relatively large area. The maximum distance for air defense radars can exceed 500 km, and the azimuth coverage is a full circle of 360 degrees. Air defense radars are usually divided into two categories depending on the amount of information transmitted about the position of the target. Radars that provide only distance and bearing information are called two-dimensional or 2D radars. Radars that provide distance, bearing, and altitude are called 3D or 3D radars. Air defense radars are used as early warning devices, as they can detect the approach of enemy aircraft or missiles at long distances. In the event of an attack, early warning about the enemy is important for organizing a successful defense against the attack. Protection against aviation in the form of anti-aircraft artillery, missiles or fighters must have a high degree of readiness in time to repel an attack. Distance and azimuth information provided by air defense radars is intended for initial positioning of radars, tracking and fire control at a target. Another function of an air defense radar is to direct a combat patrol aircraft to a position suitable for intercepting an enemy aircraft. In the case of aircraft control, information on the direction of the target's movement is obtained by the radar operator and transmitted to the aircraft either by voice to the pilot via a radio channel or via a computer line. The main applications of air defense radars: Radar is used for both military and civilian purposes. The most common civilian application is navigational aid for ships and aircraft. Radars installed on ships or at the airport collect information about other objects in order to prevent possible collisions. At sea, information is collected about buoys, rocks, etc. In the air, radars help aircraft land in conditions of poor visibility or malfunction. Radars are also used in meteorology, in forecasting weather conditions. Forecasters typically use them in conjunction with lidar (optical radar) to study storms, hurricanes, and other weather events. Doppler radar is based on the principle of the Doppler effect - that is, a change in frequency and wavelength for the observer (receiver) due to the movement of the radiation source or observer (receiver). By analyzing changes in the frequency of reflected radio waves, Doppler radar can track the movement of storms and the development of tornadoes. Scientists use radar to track the migration of birds and insects, to determine the distance to the planets. Because it can show in which direction and how fast an object is moving, radar is used by police to detect speed violations. Similar technologies are used in sports such as tennis to determine pitch speed. Radar is used by intelligence agencies to scan objects. For military purposes, radars are mainly used for target search and fire control. Radars are now used quite widely. They have found a particularly wide application in military equipment - not a single aircraft or ship can do without a radar. And ground-based radars are common. Based on their testimony, controllers control the movement and landing of aircraft, they monitor the appearance of dangerous or suspicious objects on land and at sea. Ships also have a device called an echo sounder, which works on the principle of radar, only measuring the depth under the vessel. Modern radars are capable of detecting targets hundreds of kilometers away. Entire networks of radar stations have been created that constantly "probe" the surface of the Earth in order to detect air and missile attacks. And for peaceful purposes, radars are also used - in space technology and in air transport, on ships and even on roads. The discovery of radio waves gave us not only radio, television and mobile phones, but also the ability to "see" for hundreds and thousands of kilometers in any weather, on Earth and in space. And, in conclusion - just an interesting fact. The so-called "stealth aircraft" created using the "stealth" technology, of course, are not actually invisible. To the eye, they are ordinary planes, only of an unusual shape. And the outer skin of such an aircraft is designed so that the radar beam in any position is reflected anywhere, but not back to the radar. In addition, it is made of a special polymer that absorbs most of the radio signal. That is, the radar will not receive a reflected signal from such an aircraft, which means it will not draw anything on its screen. Such is the technology war. Siemens VDO Automotive has been offering a system based on radar and vision sensors since 2003. To implement blind spot monitoring and lane change assistance, the Siemens VDO system uses a 24 GHz dual-beam radar sensor mounted on the rear bumper of the vehicle, which is both the ACU and the sensor as one component. In 2003, Denso introduced two systems, ACC and Crash Prevention, both using millimeter-wave radar and a control unit (named vehicle distance ECU for ACC and pre-crash ECU, respectively). Denso's 77 GHz radar can detect obstacles in a 20° horizontal plane with an accuracy of 0.5°. Relative speed detection range is ±200km/h (including stationary object detection), distance detection range is more than 150m. Denso's radar-based pre-crash safety system automatically activates the passenger's seat belts and the vehicle's braking system. Denso developed this system in partnership with Toyota Motor Corporation. In new cars, this system was introduced in Japan as early as 2003, and in North America in 2004. The ACC from TRW Automotive includes a 76 GHz AC20 radar sensor with FSK digital waveform, a digital processor and a controller. The radar sensor with a typical CAN interface uses a modular design based on MMIC. Distance measurements - in the range of 1–200 m with an accuracy of ± 5% or 1 m, speed measurements - in the range of ± 250 km / h with an accuracy of ± 0.1 km / h, angular measurement range of ± 6 ° with an accuracy of ± 0.3 °. The maximum deceleration during ACC intervention in the control (brake system) is limited to a limit of 0.3 g. If more deceleration is required, driver intervention is required. The required braking power in TRW systems can also be provided by the Electronic Booster, VSC/ESP. TRW's SPV/ACC can be extended with additional short range sensors (<50 м). Скоростной диапазон при этом может быть расширен до 0 км/ч, для осуществления функций, подобных Follow Stop (Follow Stop означает, что в ситуациях затора автомобиль следует за впереди идущей машиной, пока она не остановится, и автоматическую остановку хост-автомобиля, при этом возобновление движения осуществляется по нажатию кнопки водителем, в отличие от Stop&Go). Функциональность АУП и ПНУП осуществляется с дополнительными видеодатчиками. РКД от TRW предназначены также для поддержки других функций СПВ, например, мониторинга «мертвых зон». Since the ACC is often too active in control, causing many drivers to turn off cruise control, the Eaton VORAD (Vehicle Onboard RADar) radar system was developed by the manufacturer to achieve minimal system intervention in control and is marketed mainly as a means of assisting the vigilant and conscientious driver. The Eaton VORAD system consists of four main components: antenna assembly, central processing unit, driver's display, connecting harnesses. The Eaton VORAD system includes a primary forward radar for monitoring vehicles in the frontal field of view and additional side radars for blind spot monitoring and other applications. Side sensors and side touch displays are supplied as options by the manufacturer. The radar signals from the operating system always determine the distance between objects in the front of the vehicle and the relative speed and serve to warn the driver of dangerous situations through visual and audible signals only (no video playback). In addition to many standard features, options such as Fog Mode (a visual warning on the display about the presence of objects within 150 meters), adjustment of the intensity of the display based on signals from the light sensor, simultaneous tracking of up to 20 objects in front, and others are provided. The VORAD system also supports two special modes - Blind Spotter and Smart Cruise. In Blind Spotter mode, an optional side sensor, including a radar transmitter and receiver mounted on the side of the vehicle, detects moving or stationary objects from 0.3 to 3.7 m away from the vehicle. In SmartCruise mode, the vehicle maintains a set distance from the vehicle in front. Delphi introduced to the automotive market its 24 GHz UWB Forewarn Back-up Aid system integrated radar with CAN interface, designed to provide reverse assistance functions, including automatic braking upon identification of a moving or stationary obstacle. The principle of operation of the system is CW (not Doppler). Improvements include an integrated dual receiver and a visual range indicator. The dual receiver increases the measuring range to 6 m with typical reversing speeds in the range of 4.8-11.3 km/h, while extending the coverage around the corners of the vehicle. Delphi has also developed other systems for frontal and side detection of objects. Thus, the 24 GHz side detector of the RKD in the Delphi Forewarn Radar Side Alert system warns the driver about the appearance of objects in adjacent lanes within 2.4–4 m. The frontal object detection system uses a multifunctional 77 GHz RDD for detection and classification objects within a range of up to 150 m. Forewarn Smart Cruise Control, Forward Collision Warning and Collision Mitigation systems are available, for example, for the new Ford Galaxy and S-MAX vehicles. Valeo, Raytheon and M/ACOM, Continental and Hella also use 24 GHz radars for applications such as blind spot monitoring, PSP. Ru-Cyrl 18-tutorial Sypachev S.S. 1989-04-14 [email protected] Stepan Sypachev students Still not clear? - write questions to the box
Fundamental radar technologies: - OEM, Ultra-X, Ultra-K (K-Pulse)/(Smartscan™), Instant-On, POP™, HYPER-X™, HYPER-K™. Radars can combine these technologies to achieve the goals of hiding the signal from the radar detector. For example, "ISKRA 1" simultaneously uses Instant-ON as the switching mode and the PULSE + POP combination in the form of a pack of 5 short pulses. . Instant-ON is the mode of turning on the radar, when the radar is initially turned on and in standby mode, but does not emit any signal. After pressing the radar button, it instantly begins to emit a signal and measures the speed of the target at which it is directed. This allows you to remain invisible to radar detectors, which greatly increases the efficiency of the radar, as well as saves battery power of the radar. POP is a registered trademark owned by MPH Technologies. This technology, unlike Instant-ON, is responsible for the structure of the signal itself. The essence of the technology lies in the fact that the radar, after switching on, emits a very short pulse and with its help measures the speed of the target. The use of this technology complicates the detection of the radar signal by radar detectors, since many models perceive such an impulse as interference and do not issue any warning to the driver. Also, due to the too short pulse, the detection distance is significantly reduced. In order for a radar detector to recognize POP radar signals, it must be equipped with the appropriate protection technology. PULSE - in addition to POP, there is also a pulse signal technology. It differs from POP in that the pulsed signal is continuously emitted. The duration of the pulses can be different. If it is very short, this can also create a problem for the radar detector, but most modern radar detector models are equipped with pulsed radar protection. TYPE Speedcam determines the type of radar in Navitel navigation charts. . "APK "AvtoUragan" can be equipped with radar speed meters "Rapira" or "Iskra-1" when it is stationary and radar "Berkut" in the cabin of a patrol car. . "The Avtodoria registrar only works in video recorder mode. "VOCORD Traffic can be equipped with speed meters "Iskra-1"DA/130(Chris), "Iskra"DA/210, "Iskra-1"DA/60 Also, the performance of Vocord Traffic is provided in the form of radarless systems in two versions: 1 - as single blocks, where the speed measurement is based on a precise measurement of the time of each frame; 2 - in the form of several cameras for monitoring the average speed on straight sections of roads. Both Avtodoria, Avtohuragan and Vocord Traffic systems can measure the excess of the average speed on a road section. They began to install a Lira-1 radar simulator operating in the X band on the roads. Radar simulators work as false video recorders. The principle of operation is to create a radio signal similar to that emitted by road speed meters, while these devices do not have measuring devices. The SWS (Safety warning system) warning system is a messaging system for warning of approaching an emergency or accident site. The system is intended for reception with the help of radar detectors (radar detectors). The signal is transmitted at a frequency of 24.060 ... 24.140 GHz. SWS is not used in the CIS. Models can be converted into active video recorders by inserting the appropriate radar unit and connecting the camera. For many drivers, fast driving is a common occurrence. Even special electronic equipment has appeared that helps the driver avoid fines. FirstEncyclopedic YouTube
Features of the use of radar detectors and radar detectors
Laws of other countries
Duration
Songwriter
label
Britney Spears singles chronology
Release
2008
2009
Structure and lyrics
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Version 2008
Version 2009
Participation in the charts
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An excerpt characterizing Radar
As always happens during a trip, Princess Marya thought about only one trip, forgetting what was his goal. But, approaching Yaroslavl, when something that could await her again opened up, and not many days later, but this evening, Princess Mary's excitement reached its extreme limits.
When a haiduk sent ahead to find out in Yaroslavl where the Rostovs were and in what position Prince Andrei was, he met a large carriage driving in at the outpost, he was horrified to see the terribly pale face of the princess, which stuck out to him from the window.
- I found out everything, Your Excellency: the Rostov people are standing on the square, in the house of the merchant Bronnikov. Not far, above the Volga itself,” said the haiduk.
Princess Mary looked at his face in a frightened, questioning way, not understanding what he was saying to her, not understanding why he did not answer the main question: what is a brother? M lle Bourienne made this question for Princess Mary.
- What is the prince? she asked.
“Their excellencies are in the same house with them.
“So he is alive,” thought the princess, and quietly asked: what is he?
“People said they were all in the same position.
What did “everything in the same position” mean, the princess did not ask, and only briefly, glancing imperceptibly at the seven-year-old Nikolushka, who was sitting in front of her and rejoicing at the city, lowered her head and did not raise it until the heavy carriage, rattling, shaking and swaying, did not stop somewhere. The flip-up footrests rattled.
The doors opened. On the left there was water - a big river, on the right there was a porch; there were people on the porch, servants, and some sort of ruddy-faced girl with a big black plait, who smiled unpleasantly feignedly, as it seemed to Princess Marya (it was Sonya). The princess ran up the stairs, and the girl, smiling feignedly, said: “This way, this way!” - and the princess found herself in the hall in front of an old woman with an oriental type of face, who, with a touched expression, quickly walked towards her. It was the Countess. She embraced Princess Mary and began to kiss her.
– Mon enfant! she said, je vous aime et vous connais depuis longtemps. [My child! I love you and have known you for a long time.]
Despite all her excitement, Princess Marya realized that it was the countess and that she had to say something. She, not knowing how, uttered some courteous French words, in the same tone as those that were spoken to her, and asked: what is he?
“The doctor says there is no danger,” said the countess, but while she was saying this, she raised her eyes with a sigh, and in this gesture there was an expression that contradicted her words.
- Where is he? Can you see him, can you? the princess asked.
- Now, princess, now, my friend. Is this his son? she said, turning to Nikolushka, who was entering with Desalle. We can all fit, the house is big. Oh what a lovely boy!
The countess led the princess into the drawing room. Sonya was talking to m lle Bourienne. The countess caressed the boy. The old count entered the room, greeting the princess. The old count has changed tremendously since the last time the princess saw him. Then he was a lively, cheerful, self-confident old man, now he seemed a miserable, lost person. He, speaking with the princess, constantly looked around, as if asking everyone whether he was doing what was necessary. After the ruin of Moscow and his estate, knocked out of his usual rut, he apparently lost consciousness of his significance and felt that he no longer had a place in life.
Despite the excitement in which she was, despite one desire to see her brother as soon as possible and annoyance because at that moment, when she only wants to see him, she is occupied and pretended to praise her nephew, the princess noticed everything that was going on around her, and felt the need for a time to submit to this new order into which she was entering. She knew that all this was necessary, and it was difficult for her, but she did not get annoyed with them. Radars
Basic principles of radar operation
Signal processing algorithm
The main function of the radar is distance measurement
Target Elevation
Radar Antenna Gain
Antenna aperture
Noise and echoes
Classification of radar devices
Primary Radars
Secondary Radars
Classification and principal features of military radars
Radar application
Overview of some other modern radar systems
Operating principle
Related videos
Police radar classification
Main technical characteristics
Types and ranges of traffic police radars
Radar operating modes
Comparative table of police radars, photographic recorders
Model
TYPE Speedcam
Range
Frequency
Protocol
Speed range
Video range
Calibration interval
Avtodoria
4
Video
*
GPS/Glonass
10 km
*
2 years
Vocord Traffic
4
Video
*
GPS
Not ogre.
140 m
2 years
Autohurricane RS/VSM/RM
1/3/5
Video
*
*
*
*
1 year
Amata
1
Laser
800-1100 nm
-
700 m
250 m
1 year
Arena
1
K
24.125 GHz
-
1500 m
-
1 year
Barrier-2M
5
X
10.525 GHz
-
-
-
1 year
Golden eagle
5
K
24.125 GHz
K-Pulse
-
-
1 year
Binar
5
K
24.125 GHz
K-Pulse
-
-
2 years
Vizir
5
K
24.125 GHz
-
400 m
-
1 year
Iskra-1
5
K
24.125 GHz
Instant ON/PULSE/POP
400 m
-
1 year
Chris-S/P
1/5
K
24.125 GHz
-
150 m
50 m
2 years
LISD-2F
1
Laser
800-1100 nm
-
1000 m
250 m
1 year
PKS-4
1
K
24.125 GHz
-
1000 m
-
1 year
Radis
1
K
24.125 GHz
-
800 m
-
2 years
Rapier-1
1
K
24.125 GHz
-
-
20 m
2 years
Jenoptik Robot
1
K
24.125 GHz
-
-
-
-
Sokol-M
5
X
10.525 GHz
K-Pulse
-
-
1 year
Arrow ST/STM
1/5
K
24.125 GHz
K-Pulse
500 m
50 m
1 year
Radar simulators
SWS warning system
Models of video recorders
Antiradar