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38-503: The EL/W-2085 was developed from the single-band EL/M-2075 "Phalcon" system. Instead of using a rotodome , a moving radar found on some AEW&C aircraft, the EL/W-2085 uses an active electronically scanned array (AESA) – an active phased array radar. This radar consists of an array of transmit/receive (T/R) modules that allow a beam to be electronically steered, making a physically rotating rotodome unnecessary. AESA radars operate on

76-479: A beam to be electronically steered, making a physically rotating rotodome unnecessary. AESA radars operate on a pseudorandom set of frequencies and also have very short scanning rates, which makes them difficult to detect and jam . Up to 100 targets can be tracked simultaneously to a range of 200 nmi (370 km), while at the same time, over a dozen air-to-air interception or air-to-ground attack can be guided. The radar can be mounted on an aircraft's fuselage or on

114-411: A duty cycle of 3.3% can identify true range to a distance of 450 km (30 * C / 10,000 km/s). This is the instrumented range . Unambiguous velocity is 1,500 m/s (3,300 mile/hour). The unambiguous velocity of an L-Band radar using a PRF of 10 kHz would be 1,500 m/s (3,300 mile/hour) (10,000 x C / (2 x 10^9)). True velocity can be found for objects moving under 45,000 m/s if

152-427: A given time. This creates stronger reflections that make detection easier. Radar systems must balance these two competing requirements. Using older electronics, PRFs were generally fixed to a specific value, or might be switched among a limited set of possible values. This gives each radar system a characteristic PRF, which can be used in electronic warfare to identify the type or class of a particular platform such as

190-405: A prereceive/transmit unit, and a central six-way control is used to switch the pre-transmit/receive units of the different arrays on a time division basis. As used in its Chilean Boeing 707-based application, the lateral fairings measured approximately 12 × 2 m and were mounted on floating beds to prevent airframe flexing degrading the radar accuracy. Each array scans a given azimuth sector, providing

228-503: A pseudorandom set of frequencies and also have very short scanning rates, which makes them difficult to detect and jam . Up to 1000 targets can be tracked simultaneously to a range of 243 nmi (450 km), while at the same time, multitudes of air-to-air interceptions or air-to-surface (includes maritime) attacks can be guided simultaneously. The radar equipment of the Israeli CAEW consists of each one L-band radar left and right sides on

266-421: A radio frequency electromagnetic signal reflected from a target to determine information about that target. PRF is required for radar operation. This is the rate at which transmitter pulses are sent into air or space. A radar system determines range through the time delay between pulse transmission and reception by the relation: For accurate range determination a pulse must be transmitted and reflected before

304-530: A ship or aircraft, or in some cases, a particular unit. Radar warning receivers in aircraft include a library of common PRFs which can identify not only the type of radar, but in some cases the mode of operation. This allowed pilots to be warned when an SA-2 SAM battery had "locked on", for instance. Modern radar systems are generally able to smoothly change their PRF, pulse width and carrier frequency, making identification much more difficult. Sonar and lidar systems also have PRFs, as does any pulsed system. In

342-450: A skilled operator to adjust PRR to enhance and clarify the radar picture—for example in bad sea states where wave action generates false returns, and in general for less clutter, or perhaps a better return signal off a prominent landscape feature (e.g., a cliff). Pulse-repetition frequency (PRF) is the number of times a pulsed activity occurs every second. This is similar to cycle per second used to describe other types of waveforms. PRF

380-440: A solid-state L-band conformal array radar system for use on a Boeing 707 and other aircraft. Phalcon, as the complete AEW mission suite is referred to, is intended for airborne early warning, tactical surveillance of airborne and surface targets and intelligence gathering. It also integrates the command and control capabilities needed to employ this information. The system uses six panels of phased-array elements: two on each side of

418-682: A total coverage of 360°. Scanning is carried out electronically in both azimuth and elevation. Radar modes include high PRF search and full track, track-while-scan, a slow scan detection mode for hovering and low-speed helicopters (using rotor blade returns) and a low PRF ship detection mode. Instead of using a rotodome, a moving radar found on some AEW&C aircraft, the Phalcon uses the Active Electronically Scanned Array (AESA), an active phased array radar. This radar consists of an array of transmit/receive (T/R) modules that allow

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456-503: Is an airborne early warning and control (AEW&C) active electronically scanned array radar system developed by Israel Aerospace Industries (IAI) and Elta Electronics Industries of Israel . Its primary objective is to provide intelligence to maintain air superiority and conduct surveillance . It was surpassed by newer versions—the EL/W-2085 and the EL/W-2090 . The EL/M-2075 is

494-643: Is appropriate for civilian aircraft radar and weather radar . Low PRF radar have reduced sensitivity in the presence of low-velocity clutter that interfere with aircraft detection near terrain. Moving target indicator is generally required for acceptable performance near terrain, but this introduces radar scalloping issues that complicate the receiver. Low PRF radar intended for aircraft and spacecraft detection are heavily degraded by weather phenomenon, which cannot be compensated using moving target indicator. Range and velocity can both be identified using medium PRF, but neither one can be identified directly. Medium PRF

532-405: Is from 3 kHz to 30 kHz, which corresponds with radar range from 5 km to 50 km. This is the ambiguous range, which is much smaller than the maximum range. Range ambiguity resolution is used to determine true range in medium PRF radar. Medium PRF is used with Pulse-Doppler radar , which is required for look-down/shoot-down capability in military systems. Doppler radar return

570-403: Is generally not ambiguous until velocity exceeds the speed of sound. A technique called ambiguity resolution is required to identify true range and speed. Doppler signals fall between 1.5 kHz, and 15 kHz, which is audible, so audio signals from medium-PRF radar systems can be used for passive target classification. For example, an L band radar system using a PRF of 10 kHz with

608-459: Is inversely proportional to time period T {\displaystyle \mathrm {T} } which is the property of a pulsed wave. PRF is usually associated with pulse spacing, which is the distance that the pulse travels before the next pulse occurs. PRF is crucial to perform measurements for certain physics phenomenon. For example, a tachometer may use a strobe light with an adjustable PRF to measure rotational velocity. The PRF for

646-477: Is more common in device technical literature ( Electrical Engineering and some sciences), and the latter (PRR) more commonly used in military-aerospace terminology (especially United States armed forces terminologies) and equipment specifications such as training and technical manuals for radar and sonar systems. The reciprocal of PRF (or PRR) is called the pulse-repetition time ( PRT ), pulse-repetition interval ( PRI ), or inter-pulse period ( IPP ), which

684-485: Is the elapsed time from the beginning of one pulse to the beginning of the next pulse. The IPP term is normally used when referring to the quantity of PRT periods to be processed digitally. Each PRT having a fixed number of range gates , but not all of them being used. For example, the APY-1 radar used 128 IPP's with a fixed 50 range gates, producing 128 Doppler filters using an FFT. The different number of range gates on each of

722-467: Is the number of pulses of a repeating signal in a specific time unit. The term is used within a number of technical disciplines, notably radar . In radar, a radio signal of a particular carrier frequency is turned on and off; the term "frequency" refers to the carrier, while the PRF refers to the number of switches. Both are measured in terms of cycle per second , or hertz . The PRF is normally much lower than

760-406: Is utilized extensively in automated machine control systems (e.g. electric eyes controlling a garage door, conveyor sorting gates, etc.), and those that use pulse-rate detection and ranging are at heart, the same type of system as a radar—without the bells and whistles of the human interface. Unlike lower radio signal frequencies, light does not bend around the curve of the earth or reflect off

798-510: The Republic of Singapore Air Force to replace its upgraded E-2C Hawkeyes . The new G550 aircraft entered service on 13 April 2012. Italy initially purchased two G550-EL/W-2085 aircraft in 2011 and recently ordered two more in 2022. In 2018, the U.S. Navy accepted delivery of a G550-EL/W-2085 intended to be further modified by Raytheon to become the NC-37B. EL/M-2075 The EL/M-2075 Phalcon

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836-470: The EL/W-2085 dual-band sensor suite, and are more capable and less expensive to operate than the older Boeing 707 -based EL/M-2075 . Extensive modifications were made to the Gulfstream's fuselage by IAI, such as the addition of protruding composite radomes , to house the radar arrays in conformal body modifications. Based at Nevatim Airbase . In 2007, four similar G550-EL/W-2085 aircraft were purchased by

874-530: The band pass filter admits the signal (1,500/0.033). Medium PRF has unique radar scalloping issues that require redundant detection schemes. Systems using PRF above 30 kHz function better known as interrupted continuous-wave (ICW) radar because direct velocity can be measured up to 4.5 km/s at L band , but range resolution becomes more difficult. High PRF is limited to systems that require close-in performance, like proximity fuses and law enforcement radar . For example, if 30 samples are taken during

912-495: The case of sonar, the term pulse-repetition rate ( PRR ) is more common, although it refers to the same concept. Electromagnetic (e.g. radio or light) waves are conceptually pure single frequency phenomena while pulses may be mathematically thought of as composed of a number of pure frequencies that sum and nullify in interactions that create a pulse train of the specific amplitudes, PRRs, base frequencies, phase characteristics, et cetera (See Fourier Analysis ). The first term (PRF)

950-542: The first Phalcon system to be installed was fitted to a former LanChile Boeing 707, and was first flown in 1993. In May 1994, the aircraft was delivered to the Chilean Air Force , where it is known as the Condor. The Israeli Air Force installed the Phalcon system on Boeing 707 aircraft, which replaced its E-2Cs which were retired in mid-1990s. Pulse repetition frequency The pulse-repetition frequency ( PRF )

988-538: The five PRF's all being less than 50. Within radar technology PRF is important since it determines the maximum target range ( R max ) and maximum Doppler velocity ( V max ) that can be accurately determined by the radar. Conversely, a high PRR/PRF can enhance target discrimination of nearer objects, such as a periscope or fast moving missile. This leads to use of low PRRs for search radar, and very high PRFs for fire control radars. Many dual-purpose and navigation radars—especially naval designs with variable PRRs—allow

1026-454: The frequency. For instance, a typical World War II radar like the Type 7 GCI radar had a basic carrier frequency of 209 MHz (209 million cycles per second) and a PRF of 300 or 500 pulses per second. A related measure is the pulse width , the amount of time the transmitter is turned on during each pulse. After producing a brief pulse of radio signal, the transmitter is turned off in order for

1064-471: The fuselage and each one S-band antenna in nose and tail. The phased array allows positions of aircraft on operator screens to be updated every 2–4 seconds, rather than every 10 seconds as is the case on the rotodome AWACS. In 2005, the Israeli Air Force purchased five Gulfstream G550 -based Eitam aircraft to serve as the new IDF platform for its newer generation of AEW systems. The new aircraft use

1102-404: The fuselage, one in an enlarged nosecone and one under the tail. Each array consists of 768 liquid-cooled, solid-state transmitting and receiving elements, each of which is weighted in phase and amplitude. These elements are driven by individual modules and every eight modules are connected to a transmit/receive group. Groups of 16 of these eight module batches are linked back to what is described as

1140-406: The medium is liquid or air, and the frequency of the signal is either audio or ultra-sonic. Like radar, lower frequencies propagate relatively higher energies longer distances with less resolving ability. Higher frequencies, which damp out faster, provide increased resolution of nearby objects. Signals propagate at the speed of sound in the medium (almost always water), and maximum PRF depends upon

1178-434: The next pulse is transmitted. This gives rise to the maximum unambiguous range limit: The maximum range also defines a range ambiguity for all detected targets. Because of the periodic nature of pulsed radar systems, it is impossible for some radar system to determine the difference between targets separated by integer multiples of the maximum range using a single PRF. More sophisticated radar systems avoid this problem through

EL/W-2085 - Misplaced Pages Continue

1216-499: The quiescent phase between transmit pulses using a 30 kHz PRF, then true range can be determined to a maximum of 150 km using 1 microsecond samples (30 x C / 30,000 km/s). Reflectors beyond this range might be detectable, but the true range cannot be identified. It becomes increasingly difficult to take multiple samples between transmit pulses at these pulse frequencies, so range measurements are limited to short distances. Sonar systems operate much like radar, except that

1254-418: The receiver units to detect the reflections of that signal off distant targets. Since the radio signal has to travel out to the target and back again, the required inter-pulse quiet period is a function of the radar's desired range. Longer periods are required for longer range signals, requiring lower PRFs. Conversely, higher PRFs produce shorter maximum ranges, but broadcast more pulses, and thus radio energy, in

1292-492: The size of the object being examined. For example, the speed of sound in water is 1,497 m/s, and the human body is about 0.5 m thick, so the PRF for ultrasound images of the human body should be less than about 2 kHz (1,497/0.5). As another example, ocean depth is approximately 2 km, so sound takes over a second to return from the sea floor. Sonar is a very slow technology with very low PRF for this reason. Light waves can be used as radar frequencies, in which case

1330-475: The strobe light is adjusted upward from a low value until the rotating object appears to stand still. The PRF of the tachometer would then match the speed of the rotating object. Other types of measurements involve distance using the delay time for reflected echo pulses from light, microwaves, and sound transmissions. PRF is crucial for systems and devices that measure distance. Different PRF allow systems to perform very different functions. A radar system uses

1368-418: The system is known as lidar. This is short for "LIght Detection And Ranging," similar to the original meaning of the initialism "RADAR," which was RAdio Detection And Ranging. Both have since become commonly-used english words, and are therefore acronyms rather than initialisms. Laser range or other light signal frequency range finders operate just like radar at much higher frequencies. Non-laser light detection

1406-476: The top inside a small dome. Either position gives the radar 360-degree coverage. The phased array radar allows positions of aircraft on operator screens to be updated every 2–4 seconds, rather than every 20–40 seconds as is the case on the rotodome AWACS. The system can be fitted to a number of aircraft, including the Boeing 707 , Boeing 767 and Boeing 747 series aircraft. Under a contract signed with Chile in 1989,

1444-735: The use of multiple PRFs either simultaneously on different frequencies or on a single frequency with a changing PRT. The range ambiguity resolution process is used to identify true range when PRF is above this limit. Systems using PRF below 3 kHz are considered low PRF because direct range can be measured to a distance of at least 50 km. Radar systems using low PRF typically produce unambiguous range. Unambiguous Doppler processing becomes an increasing challenge due to coherency limitations as PRF falls below 3 kHz. For example, an L-Band radar with 500 Hz pulse rate produces ambiguous velocity above 75 m/s (170 mile/hour), while detecting true range up to 300 km. This combination

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