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Pulse Doppler Radar
milstar: CHAPTER 17PULSE DOPPLER RADARWilliam H. LongDavid H. MooneyWilliam A. SkillmanWestinghouse Electric Corporation17.1 CHARACTERISTICSANDAPPLICATIONSNomenclature. For the purpose of this chapter, the term pulse doppler (PD)will be used for radars to which the following apply: 1. They utilize coherent transmission and reception; that is, each transmittedpulse and the receiver local oscillator are synchronized to a free-running, highlystable oscillator .2. They use a sufficiently high pulse repetition frequency (PRF) to be ambig-uous in range. 3. They employ coherent processing to reject main-beam clutter, enhance tar-get detection, and aid in target discrimination or classification.Applications. PD is applied principally to radar systems requiring thedetection of moving targets in a severe clutter environment. Table 17.1 liststypical applications 1^0 and requirements. This chapter will deal principallywith airborne applications, although the basic principles can also be applied tothe ground-based case.PRFs. Pulse doppler radars are generally divided into two broad PRFcategories: medium and high PRF.11 In a medium-PRF radar12"14 the target andclutter ranges and velocities of interest are usually ambiguous, while in a high-PRF radar 15 the range is ambiguous but the velocity is unambiguous (or has atmost a single velocity ambiguity as discussed later).A low-PRF radar, commonly called a moving-target indicator (MTI),16 is onein which the ranges of interest are unambiguous while the velocities are usuallyambiguous. MTI radars are generally not categorized as pulse doppler radars, al-though the principles of operation are similar. A comparison of MTI and pulsedoppler radars is shown in Table 17.2 http://www.helitavia.com/skolnik/Skolnik_chapter_17.pdf TABLE 17.1 Pulse Doppler Applications and RequirementsTABLE 17.2 Comparison of MTI and Pulse Doppler (PD) RadarsPulse Doppler Spectrum. MTI- low PRF --------------------- Advantages Can sort clutter from targetson basis of range. No rangeghosts. Front-end STC sup-presses sidelobe detectionsand reduces dynamic rangerequirements Disadvantages Low doppler visibility due tomultiple blind speeds. Poorslow-moving target rejection.Cannot measure radial targetvelocity. PD- medium PRF --------------------------- Advantages Good performance at all tar-get aspects. Good slow-moving target rejection.Measures radial velocity.Less range eclipsing than inhigh PRF. Disadvantages Range ghosts. Sidelobe clut-ter limits performance. Highstability requirements due torange folding. PD- high PRF ------------------------ Advantages Can be sidelobe clutter-freefor some target aspects. Sin-gle doppler blind zone atzero velocity. Good slow-moving target rejection.Measures radial velocity.Velocity-only detection canimprove detection range. Disadvantages Sidelobe clutter limits perfor-mance. Range eclipsing.Range ghosts. High stabilityrequirements due to rangefolding.
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milstar: General. Clutter returns from various scatterers have a strong influence onthe design of a pulse doppler radar as well as an effect on the probability ofdetection of point targets. Clutter scatterers include terrain, both ground andwater, rain, snow, and chaff. Since the antennas generally used in pulsedoppler radars have a single, relatively high-gain main beam, main-beam cluttermay be the largest signal handled by the radar when in a down-look condition,which is a principal reason for the use of medium- and high-PRF pulse dopplerradars. The narrow beam limits the frequency extent of this clutter to arelatively small portion of the doppler spectrum. The remainder of the antennapattern consists of sidelobes which result in sidelobe clutter. This clutter isgenerally much smaller than the main-beam clutter but covers much more ofthe frequency domain. The sidelobe clutter from the ground directly below theradar, the altitude line, is frequently large owing to a high reflection coefficientat steep grazing angles, the large geometric area, and the short range. Rangeperformance is degraded for targets in the sidelobe clutter region wherever theclutter is near or above the receiver noise level. Multiple PRFs may be used tomove the target with respect to the clutter, thus avoiding completely blindranges or blind frequencies due to high clutter levels. This relative motionoccurs owing to the range and doppler foldover. If one PRF folds sidelobeclutter and a target to the same apparent range and doppler, a sufficient changeof PRF will separate them.
milstar: High-PRF Ranging. Range-ambiguity resolution in high PRF is performedby modulating the transmitted signal and observing the phase shift of themodulation on the return echo. Modulation methods include varying the PRF,either continuously or in discrete steps; varying the RF carrier, with eitherlinear or sinusoidal FM; or some form of pulse modulation such as pulse-widthmodulation (PWM), pulse-position modulation (PPM), or pulse-amplitudemodulation (PAM). Of these modulation techniques, PWM and PPM may havelarge errors because of clipping of the received modulation by eclipsing orstraddling (discussed in Sec. 17.7), and PAM is difficult to mechanize in boththe transmitter and the receiver. Consequently, they will not be furtherconsidered here.Multiple Discrete PRF Ranging. Ranging by use of several (usually two orthree) fixed PRFs involves sequential measurement of the ambiguous range ineach PRF, followed by comparison of the measurements to eliminateambiguities.36' http://www.helitavia.com/skolnik/Skolnik_chapter_17.pdf Figure 17.14 illustrates the principle of multiple-PRF ranging for a two-PRF,high-PRF radar. The PRFs are chosen to have a common submultiple frequency\ITU. If the transmitted-pulse trains are compared in a coincidence detector, thecommon submultiple frequency is obtained. Similarly, if the received gates arecompared in a coincidence detector, the same submultiple frequency shifted intime by the target range delay Tr is obtained. Measuring the time delay betweenthe two sets of coincidence pulses yields the true target range. If desired, a three-PRF system can be mechanized similarly. The advantage obtained is the in-creased unambiguous range achievable. Medium-PRF Ranging. Multiple discrete PRF ranging, as discussed for highPRF, is also used for medium PRF except that the PRF selection criteriondiffers.13 The technique of using closely spaced PRFs can be extended to mediumPRF by employing three groups of three closely spaced PRFs, the groups beingwidely spaced to improve doppler visibility. The center PRF in each group iscalled the major PRF, and the adjacent ones the minor PRFs. Ranging isaccomplished by requiring a detection in the major PRF and its adjacent minorPRFs and is effectively a detection criterion of exactly three detections out ofthree opportunities. This approach is attractive from a ghosting standpoint butsuffers owing to the poor doppler visibility that results from having only threePRFs visible.A better technique for medium PRF is to use seven or eight PRFs which covernearly an octave in frequency and to require detections in at least three of theseto declare a target report. The advantage is that doppler visibility is better thanwith the major-minor approach, and hence better range performance in sidelobeclutter is achieved (where some PRFs may be obscured by clutter). However, itis more susceptible to ghosting owing to the high doppler visibility. This problemis mitigated by also resolving the doppler ambiguities and using the true dopplerfor correlation to reject ghosts.The basic accuracy of multiple-PRF ranging is on the order of the range-gatesize (150 m/jjis), but this can be improved to a fraction of the gate width by am-plitude centroiding.
milstar: https://faculty.nps.edu/jenn/Seminars/RadarFundamentals.pdf In practice the received signal is "corrupted" (distorted from the ideal shape and amplitude) by thermal noise, interference and clutter.• Typical return trace appears as follows Threshold detectionis commonly used. If the return is greater than the detection threshold a target is declared. Ais a false alarm: the noise is greater than the threshold level but there is no target. Bis a miss: a target is present but the return is not detected.
milstar: Noncoherent integration(postdetectionintegration): performed after the envelope detector. The magnitudes of the returns from all pulses are added. SNR increases approximately as .•Coherent integration(predetectionintegration): performed before the envelope detector (phase information must be available). Coherent pulses must be transmitted. The SNR increases as N https://faculty.nps.edu/jenn/Seminars/RadarFundamentals.pdf
milstar: http://www.ee.fju.edu.tw/pages/032_faculty/sclin/lecture/Rada_System_Design/Chapter14.pdf
milstar: https://www.ll.mit.edu/sites/default/files/outreach/doc/2018-07/lecture%208.pdf
milstar: Radar Missile guidance http://helitavia.com/skolnik/Skolnik_chapter_19.pdf
milstar: https://www.eetimes.com/radar-basics-part-2-pulse-doppler-radar/ Doppler ambiguities Doppler ambiguities can occur if the Doppler range is larger than the PRF. For example, in military airborne radar, the fastest closing rates will be with targets approaching, as both speeds of the radar-bearing aircraft and the target aircraft are summed. This should assume the maximum speed of both aircraft. The highest opening rates might be when a target is flying away from the radar-bearing aircraft. Here, the radar-bearing aircraft is assumed to be traveling at minimum speed, as well as the target aircraft flying at maximum speed. It is also assumed that the target aircraft is flying a large angle θ from the radar-bearing aircraft flight path, which further reduces the radar-bearing aircraft speed in the direction of the target. The maximum positive Doppler frequency (fastest closing rate) at 10 GHz / 3 cm is: Radar –bearing aircraft maximum speed: 1200 mph = 536 m/s Target aircraft maximum speed: 1200 mph = 536 m/s Maximum positive Doppler = 2 (1072m/s) / (0.03m) = 71.5 kHz The maximum negative Doppler frequency (fastest opening rate) at 10 GHz / 3 cm is: Radar-bearing aircraft minimum speed: 300 mph = 134 m/s Effective radar-bearing aircraft minimum speed with θ = 60 degree angle from target track (sin (60) = 0.5): 150 mph = 67 m/s Target aircraft maximum speed: 1200 mph = 536 m/s Maximum negative Doppler = 2 (67–536 m/s) / (0.03m) = 31.3 kHz This results in a total Doppler range of 71.5 + 31.3 = 102.8 kHz. Unless the PRF exceeds 102.8 kHz, there will be aliasing of the detected Doppler rates, and the associated ambiguities. Often targets are moving, and Doppler processing is an effective method to distinguish the target from the background clutter of the ground. However, the Doppler frequency of the ground will can be non-zero if the radar is in motion. Different points on the ground will have different Doppler returns, depending on how far ahead or behind the radar-bearing aircraft that a particular patch of ground is located. Doppler sidelobe clutter can be present over a wide range of Doppler frequencies. Mainlobe clutter is more likely to be concentrated at a specific frequency, since the mainlobe is far more concentrated (typically 3 to 6 degrees of beam width), so the patch of ground illuminated is likely to be far smaller and all the returns at or near the same relative velocity.
milstar: PRF tradeoffs Different PRF frequencies have different advantages and disadvantages. The following discussion summarizes the trade-offs. Low PRF operation is generally used for maximum range detection. It usually requires a high power transmit power, in order to receive returns of sufficient power for detection at a long range. To get the highest power, long transmit pulses are sent, and correspondingly long matched filter processing (or pulse compression) is used. This mode is useful for precise range determination. Strong sidelobe returns can often be determined by their relatively close ranges (ground area near radar system) and filtered out. ----- Disadvantages are that Doppler processing is relatively ineffective due to so many overlapping Doppler frequency ranges. This limits the ability to detect moving objects in the presence of heavy background clutter, such as moving objects on the ground.
milstar: High PRF operation spreads out the frequency spectrum of the receive pulse, allowing a full Doppler spectrum without aliasing or ambiguous Doppler measurements. A high PRF can be used to determine Doppler frequency and therefore relative velocity for all targets. It can also be used when a moving object of interest is obscured by a stationary mass, such as the ground or a mountain, in the radar return. The unambiguous Doppler measurements will make a moving target stand out from a stationary background. This is called mainlobe clutter rejection or filtering. Another benefit is that since more pulses are transmitted in a given interval of time, higher average transmit power levels can be achieved. This can help improve the detection range of a radar system in high PRF mode. ------------- Medium PRF operation is a compromise. Both range and Doppler measurements are ambiguous, but each will not be aliased or folded as severely as the more extreme low or high PRF modes. This can provide a good overall capability for detecting both range and moving targets. However, the folding of the ambiguous regions can also bring a lot of clutter into both range and Doppler measurements. Small shifts in PRFs can be used to resolve ambiguities, as has been discussed, but if there is too much clutter, the signals may be undetectable or obscured in both range and Doppler. FM ranging One solution is to use the high PRF mode to identify moving targets, especially fast moving targets, and then switch to a low PRF operation to determine range. Another alternative is to use a technique called FM ranging. In this mode, the transmit duty cycle becomes 100% and the radar transmits and receives continuously The transmission is a continuously increasing frequency signal, and then at the maximum frequency, abruptly begins to continuously decrease in frequency until it reaches the minimum frequency. This cycle then repeats. The frequency over time looks like a “saw tooth wave”. The receiver can operate while during transmit operation, as the receiver is detecting time delayed versions of the transmit signal, which is at a different frequency than current transmit operation. Therefore, the receiver is not desensitized by the transmitter’s high power at the received signal frequency. Through Doppler detection of what frequency is received, and knowing the transmitter frequency ramp timing, can be used to determine round-trip delay time, and therefore range. And the receive frequency “saw tooth” will be offset by the Doppler frequency. On a rapidly closing target, the receive frequencies will be all offset by a positive fDoppler , which can be measured by the receiver once the peak receive frequency is detected. In summary, Doppler processing enables radar systems to discriminate in target velocity, as well as range and angle of the target. This is critical to distinguish moving targets from the background clutter. Doppler processing depends on frequency domain processing, which can be efficiently computed using an algorithm known as the Fast Fourier Transform, or FFT. In Part 3 of the series on radar, an examination of how beamforming, pulse compression and Doppler processing can be implemented in radar systems will be examined.
milstar: 1МОСКОВСКИЙ АВИАЦИОННЫЙ ИНСТИТУТКАФЕДРА 401А.В.БруханскийСистемы селекции движущихся целей http://kaf401.rloc.ru/files/MTI.pdf
milstar: re:параллельный прием, множество каналов в приемнике LRASM,,повсеместная РЛС 1.B-1B может нести во внутренних отсеках до 24 таких ракет массой чуть более тонны каждая. Такого количества целей технически вполне достаточно для того, чтобы обеспечить корабельной ПВО, и даже не китайской, "перегрузку по входу". Роберт Уорк, в прошлом заместитель министра обороны США. https://vpk.name/news/292117_sovetskii_metod_zachem_aviacii_vms_ssha_nuzhny_dalnie_raketonoscy.html ################################################################## 2. a. главной особенностью ЗРС «Бук-М2», ее изюминкой, являются значительно расширенные возможности по борьбе с современными КР на предельно малых высотах. Так, при полете КР на высоте 15 м дальность ее поражения составляет до 30–35 км, Это достигается за счет введения в состав ЗРС радиолокатора подсвета и наведения (РПН)-9C36M , антенные системы и приемно-передающие устройства которого размещены на мобильном телескопическом подъемно-поворотном устройстве, поднимающем их на высоту более 22 м в течение 2 мин. Александр Григорьевич Лузан, доктор технических наук, лауреат Государственной премии, генерал-лейтенант в отставке, https://www.vesvks.ru/vks/article/tomagavki-byut-po-sirii-poleznye-uroki-16280 2.b http://bastion-karpenko.ru/viking-buk-m3/ антенна бук м3 9C36M Ku -38 db ,ширина луча 1 * 2 градуса , предположительно 7.6-8 ghz , 2500 -3000 элементов при полном заполнении из расчета h/2 ... возможно реализовать среднюю мощность 10 квт при PRF =1000 ,интеграции 20 импульсов реалистичнo получить дальность обнаружения 140 километров для RCS = 1 квадратный метр,35 километров для RCS = 0.004 квадратный метра ########################## 3.повсеместный радар,параллельный прием множеством приемников в АФАР с полностью цифровым формированием лучей Dr. Eli Brookner, Raytheon http://radarconf16.org/tutorial-c3.pdf Digital Beam Forming (DBF): Israel, Thales and Australia AESAs under development have an A/D for every element channel https://apps.dtic.mil/dtic/tr/fulltext/u2/a403877.pdf Systems Aspects of Digital Beam Forming Ubiquitous Radar MERRILL SKOLNIK https://www.raytheon.com/sites/default/files/capabilities/rtnwcm/groups/public/documents/image/amdr-infographic-pdf.pdf 69 RMA ( каждый 61*61*61 сантиметр )provide SPY-1 +25 db capability can see a target of half the size at almost four times the distance 37 RMA (configuration for DDG 51 Flight 3) can see a target half the size at twice the distance of radar on today's navy destroyers Dual Axis multibeam scanning Thales http://tangentlink.com/wp-content/uploads/2014/12/4.-AESA-radars-using-Dual-axis-Multibeam-Scanning.pdf 4. один из возможных сценариев противник как в пункте 1 желает создать перегрузку po входу 96 ракет LRASM на высоте 2-5 метра в секторе 90 градусов равноудаленных от рлс на высотe 22 метра как в пункте 2 повсеместная РЛС 2500 -3000 элементов , средняя мощность передатчика = 10 квт ширина луча 2 градуса пo вертикали,1. градуса пo горизонтали передающие блоки повсеместной РЛС формируют сектор из 90 лучей 90*1 градус *2 градусa энергетический потенциал каждого луча падает в 90 раз,это компенсируется увеличением времени интеграции в 90 раз в каждом луче сектора copy from 2b при PRF =1000 ,интеграции 20 импульсов реалистичнo получить дальность обнаружения 140 километров для RCS = 1 квадратный метр,35 километров для RCS = 0.004 квадратный метра ----------------------------- 0.02 секунды *90 =1.8 сек время интеграции 1800 импульсов, вполне допустимо так как скорость LRASM =300 metr sek ,.для сравнения РЛС 300в4 ПО 9С19М1 «Имбирь-М» концентрированная для перехвата Першинг- 2 ( скорость более 3000 метров в секунду) темп обновления информации – 1 с https://www.vesvks.ru/vks/article/zenitnaya-raketnaya-sistema-s300v4--nadezhnyy-stra-16279 более детальные расчеты в тексте page 7 short -range surveillance https://apps.dtic.mil/dtic/tr/fulltext/u2/a403877.pdf Systems Aspects of Digital Beam Forming Ubiquitous Radar MERRILL SKOLNIK A radar that can detect 1 sqare metr target at 140 nmi with a 4-s revisit time can detect the same size target at 100 nmi (185.2 km) with a 1-s revisit time.(Coherent integration is assumed.) Then there is enough echo signal energy at 10nmi (18.52 km) to detect a 0.0001 m2 target with a 1-s revisit time,assuming that doppler signal processing is used that provides an adequate signal-to-clutter ratio. If the radar requires a 0.1s revisit 10 nmi =18.52 km time to guide a defensive missile to an intercept, the minimum detectable radar cross section is then 0.001 sqare metr .If it were really important to place a 0.0001 m2 cross section target in track with a 0.1s revisit time that could be done at a range of about 5.6 nmi.(10km) ##################################### 5, Российские компоненты СБИС 16-разрядного АЦП с частотой дискретизации 200 МГц https://mri-progress.ru/products/bis-i-sbis/spetsialnye-sbis/sbis-16-razryadnogo-atsp/ Микросхема интегральная 1879ВМ8Я представляет собой универсальную платформу ориентированную на решение задач обработки больших потоков данных в реальном масштабе времени (цифровая обработка сигналов, обработка изображений, навигация, связь, https://www.module.ru/products/1/26-18798
milstar: 2 -Доктрина «На войне, — оборонительный образ действий никогда не должен иметь целью только оборону; он всегда должен иметь единственной целью использование собственных средств с наибольшим коэфициентом полезного действия... Наоборот, воздушная оборона имеет целью только защиту. Она ничуть не повышает коэфициента использования воздушного оружия, а даже уменьшает его до минимума. Таким образом, она представляет собой военно-техническую ошибку» ...Наконец, есть образ, действий, повидимому, соединяющий в себе все трудности: это — оборона в воздухе. «Воздушному оружию нет надобности яростно набрасываться на небольшие объекты, так как перед ним открывается бесчисленное количество крупных и важных объектов... Воздушное оружие будет испытывать затруднения лишь в выборе. Самыми первыми объектами воздушной армии должны быть неподвижные и постоянные объекты, обслуживающие воздушные силы противника: самолетостроительные заводы, крупные склады имущества и т. п. Дуэ (сентябрь 1928 г.). ....ввести в состав дивизиона комплексы Циркон,X-95 --------------------------------------------------------- при потере связи командиру дивизиона предоставлена атаковать неподвижные цели военно-воздушных сил противника аэродромы ,пункты командования ВВС,РЛС противоракетной обороны, базы ВМФ и ВВС в том числе термоядерными боевыми блоками ----------------------- для сравнения доктрина 80 годов предполагала использование ядерного оружия как одного из средств радиоэлектронной борьбы Другой подход (с начала 60-х и до конца 80-х гг.) состоял в том, что составной частью РЭБ считалось поражение РЭС противника любыми средствами, включая даже ядерное поражение, Михаил Дмитриевич Любин - полковник в отставке, бывший старший преподаватель кафедры РЭБ Военной академии Генерального штаба. ----------------- на рисунке в статье Александр Лузан, доктор технических наук, лауреат Государственной премии РФ, генерал-лейтенант прикрытие Искандеров https://vpk-news.ru/articles/36010
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