Seeking radar
The word RADAR is an abbreviation of Radio Detecting and Ranging, which means "Detection and Radioelectronic Telemetry", representing the two basic functions of radar: discovery and localization with the help of electromagnetic waves.
Principle of operation: The radar antenna illuminates the target with a very high frequency signal, called a "poll" signal. This signal is reflected by the target and received by the receiver through the antenna. The survey signal is generated by a high-power transmitter and received by a receiver with high sensitivity. The antenna switch allows the use of the same antenna for both transmission and reception. Modern radars can extract from the echo signal other information besides distance but determining distance by measuring the delay time remains one of the main functions of the radar.
Search radars scan large volumes of space with short-wave radio pulses. It usually scans the volume two to four times per minute. Electromagnetic waves are usually less than a meter long. The radar measures the distance from the reflector by measuring the round-trip time from the emission of an impulse to the reception, dividing this by two and then multiplying by the speed of light. To be accepted, the pulse received must be in a period called the gate of range. Radar determines the direction because short radio waves behave like a search light when emitted by the radar antenna reflector.
Classification of tracking and early warning radars:
Early warning radar - Early-warning radar is a system used primarily for detectinglong distances of targets, that is, to allow alerting defenses in the shortest possible time before the intruder reaches its target, providing maximum air defenses in which to act. Early Warning radars tend to share a number of design features asthey improve performance, for example, radar usually operates at lower frequencies and therefore at longer wavelengths than other types of radar. This greatly reduces their interaction with rain and snow in the air, and therefore improves their performance in the long-term role, where their coverage area will often include precipitation. These radars often use much lower the frequency of pulse repetition to maximize their autonomy, at the cost of signal power, and compensate for this with the longwidth of the pulses, which increases the signal with the aim of reducing resolution. The first early warning radars were the British Chain Home, the German Freya, the USA CXAM (Navy) and the SCR-270 (Army) and the Soviet Union RUS-2. According to modern standards, they had a fairly short range, usually between 160 and 240 km. This "short" distance is a side effect of the propagation of their radio wavelengths used at the time, which were generally limited to the line of sight. Although long-distance propagation techniques were known and widely used for shortwave radio, the ability to process the complex return signal was simply not possible at that time.
Ground-controlled interception (GCI) is a tactical system whereby one or more radar stations or other observation stations are linked to a command communication center that guides an interceptor aircraft to an airborne target. This tactic was initiated during the First World War near the London Air Defence Zone. Today the term GCI refers to the style of the direction of battle, but during the Second World War it also referred to the radars themselves. GCI systems have increased in size and sophistication in the post-war period, as they offer much greater autonomy due to the OTH (Over-the-Horizon) system.
Airborne Early Warning and Control (AEW), the system is designed to detect aircraft, ships, and vehicles at long distances for the purpose of targeting fighter and attack aircraft. When used at altitude, the aircraft's radar allows operators to detect and track targets and distinguish between friendly and hostile aircraft much further than a similar ground radar. Just like a ground-based radar, it can be detected by opposing forces, but due to its mobility and the extended range of sensors, it is much less vulnerable to counterattacks. AEW &C aircraft are used for both defensive and offensive air operations, the system is used offensively to direct fighters to target locations and defensively, to direct counterattacks on enemy forces, both airborne and ground.
Airborne Ground Surveillance (AGS) refers to an aerial radar system used to detect and track ground targets such as slow-motion vehicles and helicopters, as opposed to early warning and air control, whose main role is the detection and tracking of their aircraft in flight. The width of the antenna beam should be very small to increase the resolution. This limitation of the size of the antenna requires a high operating frequency (GHz range) to be operated in this way. AGS radar is usually a medium or low power radar. It includes both maritime and land surveillance. Today, UAVs perform this operation, which often use optical aids for surveillance.
Over-the-horizon radar (OTH) sometimes called beyond-the-horizon (BTH), is a type of radar system with the ability to detect targets at very long distances, usually from hundreds to thousands of kilometers, beyond the radar horizon, which is the distance limit for a radar usual. Several OTH radar systems have been deployed since the 1950s and 1960s as part of early warning radars, but these have generally been replaced by airborne early warning radars. OTH radars have recently returned, as the need for precise long-distance tracking becomes less important with the end of the Cold War and less expensive land-based radars are once again being considered for roles such as maritime recognition.
Three-dimensional electronic scanning radar is a radar that uses an antenna consistingof a very large number of waveguide guides distributed over a flat surface, which scans horizontally and vertically with one or more thin beams to very quickly give a three-dimensional representation of the probed space. The phase change of the emission between each of the openings makes it possible to electronically recreate a radiation pattern similar to a parabolic antenna. By changing the phase shift, the probed direction is changed, and so it is possible to scan vertically and horizontally without having to move the antenna. Therefore, this three-dimensional electronic scanning can be done much faster than with a mechanical system, which explains its development for naval and air defense. Several ships of the national navy use it as part of highly mobile target tracking systems, such as air-to-surface missiles. The entry radar is located in Alaska and is part of the U.S. transcontinental ballistic missile defense system. The entire network will be upgraded using this type of antenna. In the case of passive electronic scanning antennas, a single source produces the wave, which is then adequately displaced for each of the radiant elements of the antenna. In active electronic scanning antennas, the antenna is in reality a set of several (from 1000 to 1500, usually) subantene independent of each other and each having its own source. The advantage of the latter approach is to be able to ensure the operation of the system after reconfiguration, even if one of the subcontractors is defective. An active antenna radar or AESA radar (Active Electronically Scanned Array) is a radar that uses the technique of the phased matrix antenna, but which does not have a single transmission antenna, but several hundred juxtaposed modules.
Classification of radars:
by their field of application:
o weather radars
o geodesy radars
o aviation radars
· by the type of platform on which it is installed:
o ground radars, which in turn can be fixed or mobile,
o airborne radars
o space cameras worn.
The classification of meteorological radars is made according to several criteria:
· according to the place where it is located:
o ground (located on the ground) which can be fixed radars and mobile radars;
o airborne (on board of some aircraft there are also meteorological radars to avoid dangerous areas for air navigation);
o spatiopurtat (on board satellites), less frequently used.
· by the wavelength used. The wavelength bands most used in the radar detection of weather targets are part of the microwave field and are:
o W band with wavelength between 0.3 and 0.8 cm and frequency between 35 and 94 GHz, for radars that detect clouds;
o K-band with wavelength between 0.8 and 2 cm and frequency between 14 and 35 GHz for rain radars;
o X band with wavelength 3 cm and frequency of about 10 GHz, for snow radars;
o C band with wavelength 5 cm and frequency of 5 GHz;
o S band with wavelength 10 cm and frequency of 3 GHz.
o The W, K, and X bands are used at medium latitudes, the C and S bands are used for rain radars at tropical latitudes.
Tracking of maneuvering targets in RLO systems. Circular vision detection radar (RLO) is designed to solve the problems of searching, detecting and tracking aerial targets, determining their nationality. RLO implements various review procedures that significantly increase noise immunity, the likelihood of detection of low-signature and high-speed targets, and the quality of tracking shunting targets. The developer of RLO is the Instrumentation Research Institute.