Форум » Дискуссии » synthetic apperture radar » Ответить
synthetic apperture radar
milstar: Nize priwedenni primeri image i movie s dowolno wisokoj razreschajuschej sposobnost'ju 100 mm dlja SAR radara w diapazonax Ka(35ghz) i Ku waznejschij wopros dlja kakoj wojni . ######################## S-300 imelo porjadka 1500 yabch . W yslowijax podriwa serii yabch w atmosfere wse eto s xoroschim chansom ne budet rabotat' Bolee wisokuju boewuju ystojchiwost' budut imet' multimegawattnie rls s bolschoj apperturoj na lampax http://www.sandia.gov/RADAR/imageryka.html kollekzija image ot 35 ghz synthetic apperture radar razr.sposobnost' 4 inches -10 sm,100 millimetr Contact: To send feedback or request information about the contents of Sandia National Laboratories' synthetic aperture radar website, please contact: Nikki L. Angus Synthetic Aperture Radar Website Owner Sandia National Laboratories Albuquerque, NM 87185-1330 (505) 844-7776 (Phone) (505) 845-5491 (Fax) nlangus@sandia.gov http://www.sandia.gov/RADAR/movies.html kollekzija video s SAR Ku band i raz sposb 300 mm
milstar: http://www.ifp.uni-stuttgart.de/publications/phowo11/160Weber.pdf Germany SAR capability
milstar: http://smaplab.ri.uah.edu/smap-center/conferences/dmsms02/presentations/freeman.pdf http://www.emsdss.com/uploadedFiles/pdf/BFN.pdf Passive Phased Arrays for Radar Antennas In fact, despite the large investment that the U.S. Government has made in the development of T/R modules beginning in 1964, the high cost and low efficiency of the modules has proven to be an obstacle to development of active phased array antennas. For example, the United Kingdom's ASTOR (Airborne Stand-Off Radar) program, which is expected to have initial operational capability in 2007 and full fleet in operation in 2008, is an airborne, ground-surveillance radar which employs a passive phased array design. Raytheon chose to use phase shifters, rather than T/R modules, citing concern over size, weight, power and technical risks. Another example is the AN/SPQ-9 Surface Surveillance and Tracking Radar, developed by Northrop Grumman Norden Systems. It is a track-while-scan radar which uses a phased array for a gunfire control system on U.S. Navy surface combatants. The antenna provides for three beams, and it will be installed on cruisers, destroyers, amphibious ships and aircraft carriers. A final example is the Joint Surveillance Target Attack Radar System (JSTARS), an airborne phased array used in a synthetic aperture radar. http://dandsmicrowave.com/papers/Brunasso_Passive%20Phased%20Arrays%20for%20Radar%20Antennas.pdf Passive Phased Arrays for Radar Antennas
milstar: http://www.help-rus-student.ru/pictures_fail/06/714_1.htm Karta Barenzewa morja ... Waznejschaja zadacha Prikriwitie PLARB Sew. Flota ,obespechenie wixoda w Arktiku Wpolne dostatochno aviazii s baz 300-400 SU35/34/PAK FA , raspolozennix na neskolkix desjatkax aerodromow ( 100 - po odnomu na zweno ?) i priktix A-2500,Buk & Kosmicheskaya i wozduschnaja razwedka Sputnikowie i troposfernie kommunikazii( ywerennaja swjaz do 600 km)
milstar: ASTOR http://www.raytheon.com/newsroom/feature/stellent/groups/public/documents/content/cms04_018168.pdf
milstar: Principles of SAR http://www.sarusersmanual.com/ManualPDF/NOAASARManual_CH01_pg001-024.pdf
milstar: Discoverer II IFSAR. http://www.jhuapl.edu/techdigest/TD/td2003/roth.pdf
milstar: http://www.eecis.udel.edu/~xma/ELEG467_667/SAR%20FINAL.pdf SAR: Range Resolution
milstar: http://spiedigitallibrary.org/proceedings/resource/2/psisdg/2747/1/98_1?isAuthorized=no Use of IF sampling and stretch processing for a lower-cost mapping radar David A. DeBell and Thomas S. Diviney Northrop Grumman Corp. (USA) IF (intermediate frequency) sampling is a method of sampling the received radar waveform out of the IF channel directly, without mixing to baseband, using a single A/D converter. The sampling rate needed is a multiple of the bandwidth of the IF filter, of the order of 3 times the -3 dB bandwidth. IF filter skirt attenuation limits aliasing effects and permits apparent undersampling of the IF frequency. Stretch processing is the method of matching the radar's LO frequency ramp rate (linear FM) to the transmit waveform's `chirp', in order to limit the IF bandwidth requirement to a value much less than the RF bandwidth and thus permit a lower rate of sampling. The combination of IF sampling and stretch processing is advantageous because A/D samplers are now able to operate at adequately short sample- and-hold aperture times, for use at IF frequencies, with a good number of bits resolution, and stretch processing can use narrow IF bandwidths. Therefore, high range resolution can be achieved at a lower cost than with quadrature channels at baseband and dual A/D's. Added benefits are the elimination of I-Q imbalance effects, A/D DC offset effects, and the need for calibration of these effects. Some A/D saturation can also be tolerated. A Fast Fourier Transform of the real sample data set is easily converted to an inphase and quadrature output data set for further operations. The paper goes into the equations and methodology of such a radar system and delineates the hardware differences between the baseband approach and the IF sampling approach. © 2004 COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
milstar: The SAR paradox --------------------- str 33 http://www.eecis.udel.edu/~xma/ELEG467_667/SAR%20FINAL.pdf – The wider the beamwidth of the smaller real aperture (antenna), the longer the synthetic aperture (for a given range) can be – The (resulting) narrower synthetic antenna beam allows for finer ultimate azimuth resolutions to be realized • More Bandwidth in our Doppler chirps! (more on this later) – Better resolution between target angles! – However: • A smaller antenna is typically lower gain and lower power – Shortens range performance • SAR azimuth resolution was shown to be independent of wavelength and range • SAR azimuth resolution was shown to depend only on the length of the synthetic aperture – The longer the aperture (the greater the integration angle), the finer the resolution • So we can just create any size aperture we want and expect the commensurate resolution? – Not really » Longer apertures are more susceptible to phase errors resulting in defocused imagery – compensation is required – Unfocused SAR - range and wavelength play a role in determining those resolutions that can be collected and processed with minimal compensation
milstar: str .21 http://www.eecis.udel.edu/~xma/ELEG467_667/SAR%20FINAL.pdf • DBS – Doppler Beam Sharpening – Crudest form of SAR processing – Allows the radar to resolve angles finer than the azimuth beam width – The radar beam illuminates all targets within its beamwidth • Suppose the beam of width Ц is pointed at look angle И – Each edge of the beam contributes a doppler return from the “clutter
milstar: http://www.eecis.udel.edu/~xma/ELEG467_667/SAR%20FINAL.pdf • Azimuth Resolution – Remember: Range Resolution is higher (better) with increased bandwidth – Azimuth resolution becomes higher (better) with increased aperture size • If properly constructed, beam-width will decrease with increased aperture size (relative to wave-length) – Narrow beams have better azimuth resolution – Azimuth resolution is limited by the beam-width at range str.11 Most modern imaging radars utilize stretch processing – ADCs with higher ENOB (effective number of bits) and better performance are available at lower frequencies • Better dynamic range and image quality • Let’s take a look at a typical radar time/frequency diagram
milstar: http://www.ll.mit.edu/publications/journal/pdf/vol12_no2/12_2radarsignalprocessing.pdf RAC Pulse Compressors for the ALCOR Radar The ARPA-Lincoln C-band Observables Radar, or ALCOR [20], on Roi-Namur, Kwajalein Atoll, Marshall Islands, had a wideband (512 MHz) 10-мseclong linear-FM transmitted-pulse waveform (see the article entitled “Wideband Radar for Ballistic Missile Defense and Range-Doppler Imaging of Satellites,” by William W. Camp et al., in this issue). ALCOR was a key tool in developing discrimination techniques for ballistic missile defense. The wide bandwidth yielded a range resolution that could resolve individual scatterers on reentering warhead-like objects. This waveform was normally processed with the STRETCH technique, which is a clever time-bandwidth exchange process developed by the Airborne Instrument Laboratory [21, 22]. The return signal is mixed with a linear-FM chirp and the low-frequency sideband is Fourier transformed to yield range information. For a variety of reasons, the output bandwidth and consequently the range window were limited. For example, the ALCOR STRETCH processor yielded only a thirty-meter data window. Therefore, examination of a number of reentry objects, or the long ionized trails or wakes behind some objects, required a sequence of transmissions.
milstar: This sequential approach was inadequate in dealing with the challenging discrimination tasks posed by reentry complexes, which consist not only of the reentry vehicle, but also a large number of other objects, including tank debris and decoys, spread out over an extended range interval. What was needed was a signal processor capable of performing pulse compression over a large range interval on each pulse. Lincoln Laboratory contracted with Hazeltine Laboratory to develop a 512-MHz-bandwidth all-range analog pulse compressor employing thirty-two parallel narrowband dispersive bridged-T networks built out of lumped components, to cover the bandwidth. The resulting processing unit, shown in Figure 3, was large (it filled about seven relay racks) and complex, and it required a great deal of tweaking to yield reasonable sidelobes. Cost and complexity loomed large when plans were made for a series of reentry tests in which matched pairs of pulse compressors would be required. In a parallel effort, the Lincoln Laboratory SAW device group was challenged to develop pulse compressors that could meet the all-range needs of ALCOR. During 1972 and 1973, Lincoln Laboratory developed a 512-MHz-bandwidth (on a 1-GHz intermediate frequency [IF]) 10-мsec RAC linear-FM pulse compressor [23]. In ALCOR, an active circuit with feedback generated the linear-FM chirp, so that the RAC devices were to function as all-range pulse compressors matched to that waveform. To suppress range sidelobes, a Hamming window was built into the RAC devices by varying the etch depth of the grooves as a function of position.
milstar: iz M.Skolnika 3 izdanie 2008 SAR ,glawa 18 http://www.scribd.com/doc/17535378/Chapter-18-Spacebased-Remote-Sensing-Radars
milstar: Glawa 17 M.Skolnik 2008. Synthetic Aperture Radar http://www.scribd.com/doc/17535220/Chapter-17-Synthetic-Aperture-Radar
milstar: Concepts and Technologies for Synthetic Aperture Radar from MEO and Geosynchronous orbits Wendy Edelstein, Soren Madsen, Alina Moussessian, and Curtis Chen Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr., Pasadena CA 91109, USA http://radar.jpl.nasa.gov/files/ref%202_SPIE%20paper.pdf
milstar: http://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011/lecture-notes/MITRES_LL_003IAP11_lec04.pdf
milstar: http://www.vega.su/publ/Monograph_Spaceborne_SARs.pdf Усовершенствованный вариант РСА «Меч-КУ» с улучшенными характери- стиками был успешно реализован в составе КА «Алмаз-1» в 1991−1992 гг. Был применен цифровой синтез радиолокационных изображений с помощью много- процессорного вычислительного комплекса ПС-2000 с алгоритмами синтеза мето- дом ускоренной прямой свертки с субапертурами [90*, 157*, 158*] (ответственный за наземную обработку Л.Б. Неронский). Достигнутая разрешающая способность радиолокационных снимков составляла 10...15 м. После завершения эксплуатации РСА «Меч-КУ» на КА «Алмаз-1» архив полу- ченных радиограмм, обработанный с помощью вычислительного комплекса на базе универсальных ЭВМ в НПО машиностроения (ныне ОАО «ВПК «НПО машино- строения»), доступен для использования заинтересованными потребителями [538]. До настоящего времени информация, полученная с помощью РСА «Меч-КУ» явля- ется наивысшим отечественным достижением в области радиолокационного зонди- рования из космоса, а, учитывая используемый в РСА отличающийся от зарубежных РСА диапазон волн 10 см, она является уникальной и в мировом масштабе.
milstar: http://www.piers.org/piersonline/pdf/Vol3No6Page943to947.pdf
milstar: 13.4.3. Многочастный бортовой радиолокационный комплекс КА «Алмаз-1В» Пример реализации принципа наращивания сложности аппаратуры с одновремен- ным расширением ее возможностей – проект бортового радиолокационного ком- плекса (БРЛК) ЭКОР-1В КА «Алмаз-1В». Его технические характеристики приве- дены в табл.°13.6 [55], а общий вид показан на рис. 13.15. При разработке БРЛК был принят ряд ключевых решений, исходя из принципов системного подхода к проектированию РСА. В БРЛК по левому борту предусмотрен обзор с помощью двух каналов – РСА S-диапазона волн и РСА/РБО X-диапазона. Использованы вол- новодно-щелевые антенны по типу антенн РСА «Меч-К» и космического РБО «Космос-364». По правому борту осуществлялся обзор с помощью РСА S- и P-диапазонов волн. В антенной системе применены три зонтичных зеркальных ан- тенны размером 3×6 м, разработанных для РСА «Траверс» космического модуля «Природа» станции МИР [55]. Хотя в трехзеркальной антенне усложнена задача формирования ДНА с малыми боковыми лепестками, но наличие отработанных образцов и технологического оборудования явилось определяющим в выборе типа антенны. Таблица 13.6. Технические характеристики БРЛК ЭКОР-В КА «Алмаз-1В» http://www.vega.su/production/detail.php?ID=17
полная версия страницы