|
Radar Jamming And Deception
Radar jamming and deception is a form of electronic countermeasures (ECMs) that intentionally sends out radio frequency signals to interfere with the operation of radar by saturating its receiver with noise or false information. Concepts that blanket the radar with signals so its display cannot be read are normally known as jamming, while systems that produce confusing or contradictory signals are known as deception, but it is also common for all such systems to be referred to as jamming. There are two general classes of radar jamming, mechanical and electronic. Mechanical jamming entails reflecting enemy radio signals in various ways to provide false or misleading target signals to the radar operator. Electronic jamming works by transmitting additional radio signals towards enemy receivers, making it difficult to detect real target signals, or take advantage of known behaviors of automated systems like radar lock-on to confuse the system. Various Electronic counter-countermeasur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Countermeasure
An electronic countermeasure (ECM) is an electrical or electronic device designed to trick or deceive radar, sonar, or other detection systems, like infrared (IR) or lasers. It may be used both offensively and defensively to deny targeting information to an enemy. The system may make many separate targets appear to the enemy, or make the real target appear to disappear or move about randomly. It is used effectively to protect aircraft from guided missiles. Most air forces use ECM to protect their aircraft from attack. It has also been deployed by military ships and recently on some advanced tanks to fool laser/IR guided missiles. It is frequently coupled with stealth advances so that the ECM systems have an easier job. Offensive ECM often takes the form of jamming. Self-protecting (defensive) ECM includes using blip enhancement and jamming of missile terminal homers. History The first example of electronic countermeasures being applied in a combat situation took place durin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Agility
Frequency agility is the ability of a radar system to quickly shift its operating frequency to account for atmospheric effects, jamming, mutual interference with friendly sources, or to make it more difficult to locate the radar broadcaster through radio direction finding. The term can also be applied to other fields, including lasers or traditional radio transceivers using frequency-division multiplexing, but it remains most closely associated with the radar field and these other roles generally use the more generic term "frequency hopping". Description Jamming Radar systems generally operate by sending out short pulses of radio energy and then turning off the broadcaster and listening for the returning echoes from various objects. Because efficient signal reception requires careful tuning throughout the electronics in the transceiver, each operating frequency required a dedicated transceiver. Due to the size of the tube-based electronics used to construct the transceivers, early ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar Cross-section
Radar cross-section (RCS), denoted σ, also called radar signature, is a measure of how detectable an object is by radar. A larger RCS indicates that an object is more easily detected. An object reflects a limited amount of radar energy back to the source. The factors that influence this include: *the material with which the target is made; *the size of the target relative to the wavelength of the illuminating radar signal; *the absolute size of the target; *the incident angle (angle at which the radar beam hits a particular portion of the target, which depends upon the shape of the target and its orientation to the radar source); *the reflected angle (angle at which the reflected beam leaves the part of the target hit; it depends upon incident angle); *the polarization of the radiation transmitted and received with respect to the orientation of the target. While important in detecting targets, strength of emitter and distance are not factors that affect the calculation o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar Burn Through
Radar is a system that uses radio waves to determine the distance (''ranging''), direction (azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft, ships, spacecraft, guided missiles, motor vehicles, map weather formations, and terrain. The term ''RADAR'' was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term ''radar'' has since entered English and other languages as an anacronym, a common noun, losing all capitalization. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwave domain, a transmitting antenna (radio), antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a radio receiver, receiver and Data processing system, processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capital Ship
The capital ships of a navy are its most important warships; they are generally the larger ships when compared to other warships in their respective fleet. A capital ship is generally a leading or a primary ship in a naval fleet. Strategic implications There is usually no formal criterion for the classification, but it is a useful concept in naval strategy; for example, it permits comparisons between relative naval strengths in a theatre of operations without the need for considering specific details of tonnage or gun diameters. A notable example of this is the Alfred Thayer Mahan, Mahanian doctrine, which was applied in the Sinking of Prince of Wales and Repulse, planning of the defence of Singapore in World War II, where the Royal Navy had to decide the allocation of its battleships and battlecruisers between the Atlantic and Pacific theatres. The Mahanian doctrine was also applied by the Imperial Japanese Navy, leading to its Preventive war, preventive move to Attack on P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escort Ship
Ocean escort was a type of United States Navy warship. They were an evolution of the World War II destroyer escort types. The ocean escorts were intended as convoy escorts and were designed for mobilization production in wartime or low-cost mass production in peacetime. They were commissioned from 1954 through 1974, serving in the Cold War and the Vietnam War. Designation The ocean escorts' hull classification symbol was DE, a carryover from the World War II era when vessels of similar size and role were classified as destroyer escorts. DEs were ASW vessels; DEGs were ASW and AAW vessels with the short-range Tartar guided missile added. Ships similar or identical to the World War II destroyer escorts and the Cold War ocean escorts were called "frigates" in most other navies. Outside the US Navy, no other navy appears to have used the ship type of "ocean escort". The closest equivalents in type name are the Soviet and classes, built circa 1954–65. These classes' Russian de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blip Enhancement
Blip enhancement is an electronic warfare technique used to fool radar. When the radar transmits a burst of energy some of that energy is reflected off a target and is received back at the radar and processed to determine range and angle. The reflected target energy is called skin return, and the amount of energy returning to the originating radar is directly proportional to the radar cross-section (RCS) of the target. Basic radars present the target information on a display and displayed targets are referred to as blips. Based on the relative size of the blips on the display, a radar operator could determine large targets from small targets. When a blip enhancing technique is used, small targets returns are augmented to look like large targets. One early maritime application of this technique was used with an aircraft carrier and its escort ships. Because the aircraft carrier physically dwarfed the other vessels its radar return was much larger making it relatively easy for a r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Range Gate Pull-off
Range gate pull-off (RGPO) is an electronic warfare technique used to break radar lock-on. The basic concept is to produce a pulse of radio signal similar to the one that the target radar would produce when it reflects off the aircraft. This second pulse is then increasingly delayed in time so that the radar's range gate begins to follow the false pulse instead of the real reflection, pulling it off the target. Doppler radars may not use range gates and instead select a single target by narrowly filtering frequencies on either side of the target's initial return. Against these radars, the related velocity gate pull-off (VGPO) can be used. These send a return signal that slowly changes in frequency, rather than time, hoping the radar's velocity gate will be pulled off the target in the same general fashion. Pull-off belongs to the wider family of "deceptive jamming" concepts that use details of the target radar to their advantage, rather than attempting to simply overpower the rad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplitude Modulation
Amplitude modulation (AM) is a signal modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the instantaneous amplitude of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its Phase (waves), phase, as in phase modulation. AM was the earliest modulation method used for transmitting audio in radio broadcasting. It was developed during the first quarter of the 20th century beginning with Roberto Landell de Moura and Reginald Fessenden's radiotelephone experiments in 1900. This original form of AM is sometimes called double-sideband amplitude modulation (DSBAM), because the standard method produces sidebands on either side of the carrier frequency. Single-sideband modulation uses bandpass filters to eliminate one of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Repeater
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate. There are several different types of repeaters; a telephone repeater is an amplifier in a telephone line, an optical repeater is an optoelectronic circuit that amplifies the light beam in an optical fiber cable; and a radio repeater is a radio receiver and transmitter that retransmits a radio signal. A broadcast relay station is a repeater used in broadcast radio and television. Overview When an information-bearing signal passes through a communication channel, it is progressively degraded due to loss of power. For example, when a telephone call passes through a wire telephone line, some of the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AMES Type 85
The AMES Type 85, also known by its rainbow code Blue Yeoman, was an extremely powerful early warning (EW) and fighter direction (GCI) radar used by the Royal Air Force (RAF) as part of the Linesman/Mediator radar network. First proposed in early 1958, it was eleven years before they became operational in late 1968, by which time they were already considered obsolete. The Type 85 remained the RAF's primary air defense radar until it was replaced by Marconi Martello sets in the late-1980s as part of the new IUKADGE network. In the 1950s the RAF deployed the ROTOR reporting network, and later improved this system with the AMES Type 80 radar. While these were being built, the carcinotron radar jammer was tested against it and found to completely blank out its display. At first, it was feared the carcinotron would render all long-range radars useless, but over time a number of new concepts emerged to deal with this threat. Among them was the Blue Riband radar, which used a doze ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
