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Type 518 Radar
The Type 518 radar is a Chinese high-performance L band long-range shipboard air surveillance radar. The Type 518 radar may be installed on destroyers or heavy tonnage naval vessels to detect long-range high-altitude aircraft in adverse natural noise and active electronic jamming environments. The Type 518 has been installed and deployed on the Luhu-class destroyer and the Type 052D destroyer. It is manufactured and exported by the Nanjing Changjiang Machinery Group Co Ltd (南京长江机器集团电子装备有限公司). Specifications * L - band * Wide frequency band, pulse-to-pulse frequency jump * 4 phase code pulse compression technology * Low sidelobe super cosecant squared antenna * Counter electronic countermeasure and noise suppression capability * Adaptive MTI filters for noise map and speed map are provided. * Interference analysis and selected transmission technology * Other reported names: ** REL-2 (export, company) ** Hai Ying See also * Type 052 Luhu class des ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L Band
The L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz). This is at the top end of the ultra high frequency (UHF) band, at the lower end of the microwave range. Applications Mobile service In Europe, the Electronic Communications Committee (ECC) of the European Conference of Postal and Telecommunications Administrations (CEPT) has harmonized part of the L band (1452–1492 MHz), allowing individual countries to adopt this spectrum for terrestrial mobile/fixed communications networks supplemental downlink (MFCN SDL). By means of carrier aggregation, an LTE-Advanced or UMTS/HSDPA base station could use this spectrum to provide additional bandwidth for communications from the base station to the mobile device; i.e., in the downlink direction. In the Americas, mobile services are operated between the 1.7 GHz to 2.1 GHz range in the PCS and AWS bands. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Surveillance Radar
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Jamming
Radio jamming is the deliberate jamming, blocking or interference with wireless communications.https://apps.fcc.gov/edocs_public/attachmatch/DA-12-347A1.pdf Enforcement Advisory No. 2012-02 FCC Enforcement Advisory Cell Jammers, GPS Jammers, and Other Jamming Devices Consumer Alert: Using or Importing Jammers is Illegal In some cases, jammers work by the transmission of radio signals that disrupt communications by decreasing the signal-to-noise ratio. The concept can be used in wireless data networks to disrupt information flow. It is a common form of censorship in totalitarian countries, in order to prevent foreign radio stations in border areas from reaching the country. Jamming is usually distinguished from interference that can occur due to device malfunctions or other accidental circumstances. Devices that simply cause interference are regulated differently. Unintentional "jamming" occurs when an operator transmits on a busy frequency without first checking whether it is in u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luhu Class Destroyer
The Type 052 (NATO/ OSD Luhu-class destroyer is a class of destroyers developed in the People's Republic of China (PRC) for the People's Liberation Army Navy (PLAN). The Type 052 was an intermediate between the obsolescent Type 051Kirchberger (2015): page 186 and the modern Type 052B destroyers.Kirchberger (2015): page 195McDevitt (2017): page 57 They were the first PLAN destroyers powered by gas turbines, and the first PLAN ships with modern combat direction systems (CDS). They were also part of the first generation of PLAN warships armed with surface-to-air missiles in the form of the short-range Crotale (called HQ-7 in Chinese service.)Kirchberger (2015): page 231 The Type 052 used subsystems imported from the United States and the European Union. The embargo after the 1989 Tiananmen Square protests and massacre ended the supply of and support for those subsystems, limiting production to two ships and likely impacting their operating efficiency due to system integration iss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type 052D Destroyer
The Type 052D destroyer (NATO/ OSD Luyang III-class destroyer) is a class of guided-missile destroyers in the Chinese People's Liberation Army Navy. The Type 052D is a larger variant of the Type 052C; the Type 052D uses a canister-type, instead of revolver-type, vertical launching system (VLS)Li: page 44 and has flat-panelled active electronically scanned array (AESA) radar.McDevitt: page 62 The new VLS is not limited to surface-to-air missiles, making the Type 052D China's first dedicated multi-role destroyer. Etymology Chinese media informally calls the Type 052D the Chinese Aegis, portraying it as a peer of contemporary United States Navy ships equipped with the Aegis Combat System.Holmes: page 4 The appearance of the Type 052D, with flat-panelled radar and canister-based VLS, has encouraged this informal use. Design Sensors The Type 052D is equipped with Type 346A AESA and Type 518 L-band radar. The Type 052D is also equipped with both variable depth (VDS) and linear tow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanjing Changjiang Machinery Group Co Ltd
Nanjing (; , Mandarin pronunciation: ), alternately romanized as Nanking, is the capital of Jiangsu province of the People's Republic of China. It is a sub-provincial city, a megacity, and the second largest city in the East China region. The city has 11 districts, an administrative area of , and a total recorded population of 9,314,685 . Situated in the Yangtze River Delta region, Nanjing has a prominent place in Chinese history and culture, having served as the capital of various Chinese dynasties, kingdoms and republican governments dating from the 3rd century to 1949, and has thus long been a major center of culture, education, research, politics, economy, transport networks and tourism, being the home to one of the world's largest inland ports. The city is also one of the fifteen sub-provincial cities in the People's Republic of China's administrative structure, enjoying jurisdictional and economic autonomy only slightly less than that of a province. Nanjing has been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse Compression
Pulse compression is a signal processing technique commonly used by radar, sonar and echography to increase the range resolution as well as the signal to noise ratio. This is achieved by modulating the transmitted pulse and then correlating the received signal with the transmitted pulse. Simple pulse Signal description The simplest signal a pulse radar can transmit is a sinusoidal-amplitude pulse, A and carrier frequency, f_0, truncated by a rectangular function of width, T. The pulse is transmitted periodically, but that is not the main topic of this article; we will consider only a single pulse, s. If we assume the pulse to start at time t=0, the signal can be written the following way, using the complex notation: :s(t) = \begin A e^ &\text \; 0 \leq t where it reaches its maximum 1, and it decreases linearly on ,\frac{1}{2}/math> until it reaches 0 again. Figures at the end of this paragraph show the shape of the intercorrelation for a sample signal (in red), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sidelobe
In antenna engineering, sidelobes are the lobes (local maxima) of the far field radiation pattern of an antenna or other radiation source, that are not the ''main lobe''. The radiation pattern of most antennas shows a pattern of "''lobes''" at various angles, directions where the radiated signal strength reaches a maximum, separated by "''nulls''", angles at which the radiated signal strength falls to zero. This can be viewed as the diffraction pattern of the antenna. In a directional antenna in which the objective is to emit the radio waves in one direction, the lobe in that direction is designed to have a larger field strength than the others; this is the "''main lobe''". The other lobes are called "''sidelobes''", and usually represent unwanted radiation in undesired directions. The sidelobe directly behind the main lobe is called the back lobe. The longer the antenna relative to the radio wavelength, the more lobes its radiation pattern has. In transmitting antennas, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosecant Squared Antenna
A cosecant squared antenna, sometimes known as a constant height pattern, is a modified form of parabolic reflector used in some radar systems. It is shaped to send more radio energy in certain directions in order to smooth out the reception pattern of objects as their range changes in relation to the radar. The name refers to the fact that the amount of energy returned from a target drops off with the square of the cosecant of the angle between the radar and the target. Development The concept originated as part of the development of the H2S radar, which scanned the area under an aircraft to provide a radar map of the ground below. The ground directly below the aircraft is at a distance equal to the aircraft's altitude, which produces the strongest signal. The terrain at further distances returns much less signal due to the radar equation. The slant range distance between the radar and the terrain is the cosecant of the angle between the fuselage and the target, and the energy fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Counter Electronic Countermeasure
Electronic counter-countermeasures (ECCM) is a part of electronic warfare which includes a variety of practices which attempt to reduce or eliminate the effect of electronic countermeasures (ECM) on electronic sensors aboard vehicles, ships and aircraft and weapons such as missiles. ECCM is also known as electronic protective measures (EPM), chiefly in Europe. In practice, EPM often means resistance to jamming. A more detailed description defines it as the electronic warfare operations taken by a radar to offset the enemy's countermeasure. History Ever since electronics have been used in battle in an attempt to gain superiority over the enemy, effort has been spent on techniques to reduce the effectiveness of those electronics. More recently, sensors and weapons are being modified to deal with this threat. One of the most common types of ECM is radar jamming or spoofing. This originated with the Royal Air Force's use of what they codenamed ''Window'' during World War II, which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Suppression
Active noise control (ANC), also known as noise cancellation (NC), or active noise reduction (ANR), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in commercial airline headsets with the technology becoming available in the late 1980s. The technology is also used in road vehicles, mobile telephones, earbuds, and headphones Explanation Sound is a pressure wave, which consists of alternating periods of compression and rarefaction. A noise-cancellation speaker emits a sound wave with the same amplitude but with inverted phase (also known as antiphase) relative to the original sound. The waves combine to form a new wave, in a process called interference, and effectively cancel each other out – an effect which is called destructive interference. Modern active noise control is generally achiev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Radars
The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, as well as certain large, entirely landlocked, saltwater lakes, such as the Caspian Sea. The sea moderates Earth's climate and has important roles in the water, carbon, and nitrogen cycles. Humans harnessing and studying the sea have been recorded since ancient times, and evidenced well into prehistory, while its modern scientific study is called oceanography. The most abundant solid dissolved in seawater is sodium chloride. The water also contains salts of magnesium, calcium, potassium, and mercury, amongst many other elements, some in minute concentrations. Salinity varies widely, being lower near the surface and the mouths of large rivers and higher in the depths of the ocean; however, the relative proportions of dissolved salts vary li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
