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Radar Countermeasure
Radar jamming and deception is a form of electronic countermeasures 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 counter-countermeasures can sometimes hel ... [...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 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barrage Jamming
Barrage jamming is an electronic warfare technique that attempts to blind ("jam") radar systems by filling the display with noise, rendering the broadcaster's ''blip'' invisible on the display, and often those in the nearby area as well. "Barrage" refers to systems that send signals in many bands of frequencies compared to the bandwidth of any single radar. This allows the jammer to jam multiple radars at once, and reduces or eliminates the need for adjustments to respond to any single radar. Early radar systems typically operated on a single frequency, and could only change that frequency by changing internal electronics. Against these radars, it was possible to use conventional radio sets to send out signals on the same band, causing the radar display to be filled with noise whenever the antenna was pointed in the general direction of the jammer. However, given that each individual radar would be operating on different frequencies, this " spot jamming" technique required multipl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Radiated Power
Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would have to be radiated by a half-wave dipole antenna to give the same radiation intensity (signal strength or power flux density in watts per square meter) as the actual source antenna at a distant receiver located in the direction of the antenna's strongest beam (main lobe). ERP measures the combination of the power emitted by the transmitter and the ability of the antenna to direct that power in a given direction. It is equal to the input power to the antenna multiplied by the gain of the antenna. It is used in electronics and telecommunications, particularly in broadcasting to quantify the apparent power of a broadcasting station experienced by listeners in its reception area. An alternate parameter that measures the same thing is effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar Cross-section
Radar cross-section (RCS), 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 transmitted and the received radiation 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 of an RCS becaus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar Burn Through
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds. Radar was developed secretly for military use by several countries in the period before and during World War II. A key development was the cavity magnetron in the United Kingdom, which allowed the creation of relatively small systems with sub-meter resolution. The t ... [...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 Mahanian doctrine, which was applied in the 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 move to attack Pearl Harbor and the battleships of the U.S. Pacific Fleet. The naval nature of ... [...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 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 radar o ... [...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 radar' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplitude Modulation
Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) 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, 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 sidebands and ... [...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 powe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Radio Frequency Memory
Digital Radio Frequency Memory (DRFM) is an electronic method for digitally capturing and retransmitting RF signals. DRFM systems are typically used in radar jamming, although applications in cellular communications are becoming more common. Overview A DRFM system is designed to digitize an incoming RF input signal at a frequency and bandwidth necessary to adequately represent the signal, then reconstruct that RF signal when required. The most significant aspect of DRFM is that as a digital "duplicate" of the received signal, it is coherent with the source of the received signal. As opposed to analog "memory loops", there is no signal degradation caused by continuously cycling the energy through a front-end amplifier which allows for greater range errors for reactive jamming and allows for predictive jamming. A DRFM system may modify the signal prior to retransmitting which can alter the signature of the false target; adjusting its apparent radar cross section, range, velocity, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_underway_in_the_Atlantic_Ocean_on_28_May_1954.jpg "Click for more on -> Escort Ship")
