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633:, but ensuring proper account of the processing gain and external noise limitations is taken. Furthermore, unlike conventional radar, the detection range is also a function of the deployment geometry, as the distance of the receiver from the transmitter determines the level of external noise against which the targets must be detected. However, as a rule of thumb, it is reasonable to expect a passive radar using FM radio stations to achieve detection ranges of up to 150 km, for high-power analogue TV and US HDTV stations to achieve detection ranges of over 300 km and for lower power digital signals (such as cell phone and DAB or DVB-T) to achieve detection ranges of a few tens of kilometres.
931:(IFFT). Herman, Moulin, Ehrman and Lanterman have published reports based on simulated data, which suggest that low-frequency passive radars (using FM radio transmissions) could provide target classification in addition to tracking information. These Automatic Target Recognition systems use the power received to estimate the RCS of the target. The RCS estimate at various aspect angles as the target traverses the multistatic system are compared to a library of RCS models of likely targets to determine target classification. In the latest work, Ehrman and Lanterman implemented a coordinated flight model to further refine the RCS estimate.
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those on the other transmitters. Having associated these returns, the point at which the bistatic range ellipses from each transmitter intersect is the location of the target. The target can be located much more accurately in this way, than by relying on the intersection of the (inaccurate) bearing measurement with a single range ellipse. Again the optimum approach is to combine the measurements from each transmitter using a non-linear filter, such as the extended or unscented Kalman filter.
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is developing an in-orbit system to detect and track space debris from small fragments to inactive satellites. The work, supported by the UK and
European Space Agencies, is a collaboration between the Aerospace Centre of Excellence and the Centre for Signal & Image Processing at the University of
943:
operate a distributed passive radar exploiting FM broadcasts to study ionospheric turbulence at altitudes of 100 km and ranges out to 1200 km. Meyer and Sahr have demonstrated interferometric images of ionospheric turbulence with an angular resolution of 0.1 degrees, while also resolving
294:
Satellite signals have generally been found more difficult for passive radar use, either because the powers are too low or because the orbits of the satellites are such that illumination is too infrequent. However, there have been significant developments in the area over the past years. The possible
587:
When multiple transmitters are used, a target can be potentially detected by every transmitter. The return from this target will appear at a different bistatic range and
Doppler shift with each transmitter and so it is necessary to determine which target returns from one transmitter correspond with
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are capable of achieving somewhat greater accuracies. Most passive radars are two-dimensional, but height measurements are possible when the deployment is such that there is significant variation in the altitudes of the transmitters, receiver and target, reducing the effects of geometrical dilution
526:
imposed on the echo means that it will not correlate with the direct signal from the transmitter. As a result, the cross-correlation processing must implement a bank of matched filters, each matched to a different target
Doppler shift. Efficient implementations of the cross-correlation processing
465:
With some transmitter types, it is necessary to perform some transmitter-specific conditioning of the signal before cross-correlation processing. This may include high-quality analogue bandpass filtering of the signal, channel equalization to improve the quality of the reference signal, removal of
216:
that was so powerful it appeared to render long-distance radars useless. Winkle was able to home in on carcinotron broadcasts with the same accuracy as conventional radar, allowing the jammer aircraft to be tracked and attacked at hundreds of miles range. Additionally, by indicating the location of
89:
of the echo and also its direction of arrival. These allow the location, heading and speed of the object to be calculated. In some cases, multiple transmitters and/or receivers can be employed to make several independent measurements of bistatic range, Doppler and bearing and hence significantly
80:
In a passive radar system, there is no dedicated transmitter. Instead, the receiver uses third-party transmitters in the environment and measures the time difference of arrival between the signal arriving directly from the transmitter and the signal arriving via reflection from the object. This
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digital audio standard) used throughout most of the rest of the world is more challenging— transmitter powers are lower, and many networks are set up in a "single frequency network" mode, in which all transmitters are synchronised in time and frequency. Without careful processing, the net
612:, then it is possible to detect and track targets in an alternative way. Over time, moving targets will impose a changing Doppler shift and direction of arrival on the CW tone that is characteristic of the location, speed and heading of the target. It is therefore possible to use a non-linear
232:
techniques to achieve sufficient signal processing gain to detect targets and estimate their bistatic range and
Doppler shift. Classified programmes existed in several nations, but the first announcement of a commercial system was by Lockheed-Martin Mission Systems in 1998, with the commercial
200:
in 1936. The monostatic systems were much easier to implement since they eliminated the geometric complexities introduced by the separate transmitter and receiver sites. In addition, aircraft and shipborne applications became possible as smaller components were developed. In the early 1950s,
392:
A passive radar system must detect very small target returns in the presence of very strong, continuous interference. This contrasts with a conventional radar, which listens for echoes during the periods of silence in between each pulse transmission. As a result, the receiver must have a low
521:
and also provides the estimates of the bistatic range and bistatic
Doppler shift of each target echo. Most analogue and digital broadcast signals are noise-like in nature, and as a consequence, they tend to only correlate with themselves. This presents a problem with moving targets, as the
157:
Early radars were all bistatic because the technology to enable an antenna to be switched from transmit to receive mode had not been developed. Thus many countries were using bistatic systems in air defence networks during the early 1930s. For example, the
British deployed the
1708:
Theodorou, Ilias; Ilioudis, Christos; Clemente, Carmine; Vasile, Massimiliano; Soraghan, John: 'SISAR imaging for space debris based on nanosatellites', IET Radar, Sonar & Navigation, 2020, 14, (8), p. 1192-1201, {{DOI: 10.1049/iet-rsn.2019.0574}} IET Digital
Library,
405:. Despite this, the received echoes are normally well below the noise floor and the system tends to be externally noise limited (due to reception of the transmitted signal itself, plus reception of other distant in-band transmitters). Passive radar systems use
636:
Passive radar accuracy is a strong function of the deployment geometry and the number of receivers and transmitters being used. Systems using only one transmitter and one receiver will tend to be much less accurate than conventional surveillance radars, whilst
814:
Research on passive radar systems is of growing interest throughout the world, with various open-source publications showing active research and development in the United States (including work at the Air Force
Research Labs, Lockheed-Martin Mission Systems,
1681:
A. R. Persico, P. Kirkland, C. Clemente, J. J. Soraghan and M. Vasile, "CubeSat-Based
Passive Bistatic Radar for Space Situational Awareness: A Feasibility Study," in IEEE Transactions on Aerospace and Electronic Systems, vol. 55, no. 1, pp. 476-485, Feb.
879:. The low-cost nature of the system makes the technology particularly attractive to university laboratories and other agencies with limited budgets, as the key requirements are less hardware and more algorithmic sophistication and computational power.
1735:
Kulpa K., and Czekała Z.: "Long-Range
Performance Increase in Passive PCL Radar", 3rd Multinational Conference on Passive and Covert Radar, 2003 (PCR-2003). University of Washington Applied Physics Laboratory, Seattle, Washington, 21–23 October
576:. However, errors in bearing and range tend to make this approach fairly inaccurate. A better approach is to estimate the target state (location, heading and speed) from the full measurement set of bistatic range, bearing and Doppler using a
616:
to estimate the state of the target from the time history of the Doppler and bearing measurements. Work has been published that has demonstrated the feasibility of this approach for tracking aircraft using the vision carrier of
965:
with plans to scale the technology globally. Silentium has a range of products that support both tactical and strategic applications ranging from drone detection, maritime surveillance to long-range air and space search. The
201:
bistatic systems were considered again when some interesting properties of the scattered radar energy were discovered, indeed the term "bistatic" was first used by Siegel in 1955 in his report describing these properties.
319:
in the receiver. A passive radar does not have this information directly and hence must use a dedicated receiver channel (known as the "reference channel") to monitor each transmitter being exploited, and dynamically
927:. Using multiple transmitters at different frequencies and locations, a dense data set in Fourier space can be built for a given target. Reconstructing the image of the target can be accomplished through an inverse
1748:
M. Malanowski, "Influence of Integration Time on Tracking Performance in PCL Radar", Proc. Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments, vol. 6937, 28 December
571:
In a simple bistatic configuration (one transmitter and one receiver) it is possible to determine the location of the target by simply calculating the point of intersection of the bearing with the bistatic-range
42:
systems that detect and track objects by processing reflections from non-cooperative sources of illumination in the environment, such as commercial broadcast and communications signals. It is a specific case of
535:
waveforms. The signal processing gain is typically equal to the time-bandwidth product, BT, where B is the waveform bandwidth and T is the length of the signal sequence being integrated. A gain of 50
478:
The principal limitation in detection range for most passive radar systems is the signal-to-interference ratio, due to the large and constant direct signal received from the transmitter. To remove this, an
1731:
Howland, P.E., Maksimiuk, D., and Reitsma, G.: "FM radio-based bistatic radar", Radar, Sonar and Navigation, IEE Proceedings, Vol. 152, Issue 3, 3 June 2005 pp. 107 – 115, Digital Object Identifier
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H. D. Griffiths, C. J. Baker, J. Baubert, N. Kitchen, M. Treagust, "Bistatic radar using satellite-borne illuminators of opportunity", Proc. International Conference RADAR 2002, pp. 1–5, October 2002
1698:
Theodorou, I., Clemente, C., & Vasile, M. (2017). A passive debris tracking system in support of future space traffic management. Paper presented at 15th Reinventing Space Conference, Glasgow, United
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signals. However, track initiation is slow and difficult, and so the use of narrowband signals is probably best considered as an adjunct to the use of illuminators with better ambiguity surfaces.
1820:
971:
Strathclyde. Clemente and Vasile have demonstrated the technical feasibility of the detection of small pieces of debris using a range of existing illuminators and a receiver in Low Earth Orbit.
224:
The rise of cheap computing power and digital receiver technology in the 1980s led to a resurgence of interest in passive radar technology. For the first time, these allowed designers to apply
1478:
1804:
at the IEE website, which was on the subject of "Passive Covert Radar: Watson-Watt's Daventry Experiment Revisited". This includes a summary of the work in this field since World War II.
559:
The line-tracking step refers to the tracking of target returns from individual targets, over time, in the range-Doppler space produced by the cross-correlation processing. A standard
311:
In a conventional radar system, the time of transmission of the pulse and the transmitted waveform is exactly known. This allows the object range to be easily calculated and for a
449:. Alternatively, some research systems have used only a pair of antenna elements and the phase-difference of arrival to calculate the direction of arrival of the echoes (known as
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network could reduce the sensitivity of their receivers when pointed in that direction, thereby reducing the amount of jamming received when pointed near the jammer's location.
93:
The term "passive radar" is sometimes used incorrectly to describe those passive sensors that detect and track aircraft by their RF emissions (such as radar, communications, or
547:
Targets are detected on the cross-correlation surface by applying an adaptive threshold and declaring all returns above this surface to be targeted. A standard cell-averaging
77:
to transmit and receive. A pulsed signal is transmitted and the time taken for the pulse to travel to the object and back allows the range of the object to be determined.
710:
490:
In a few specific cases, the direct interference is not a limiting factor, due to the transmitter being beyond the horizon or obscured by terrain (such as with the
487:. This step is essential to ensure that the range/Doppler sidelobes of the direct signal do not mask the smaller echoes in the subsequent cross-correlation stage.
908:
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that yields a highly ambiguous or inaccurate result when cross-correlated. In this case, the processing described above is ineffective. If the signal contains a
189:, was deployed at seven sites (Limmen, Oostvoorne, Ostend, Boulogne, Abbeville, Cap d'Antifer and Cherbourg) and operated as bistatic receivers, using the British
131:
The concept of passive radar detection using reflected ambient radio signals emanating from a distant transmitter is not new. The first radar experiments in the
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Passive radar systems are currently under development in several commercial organizations. Of these, the systems that have been publicly announced include:
1739:
K. Kulpa, Z. Czekala, "Masking Effect and its Removal in PCL Radar," IEE Proc. Radar, Sonar and Navigation, vol. 152, Issue 3, pp. 174 – 178, June 2005
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is not uncommon. Extended integration times are limited by the motion of the target and its smearing in range and Doppler during the integration period.
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Passive radar performance is comparable to conventional short and medium-range radar systems. The detection range can be determined using the standard
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Howland, P.E.: "A Passive Metric Radar Using the Transmitters of Opportunity", Int. Conf.on Radar, Paris, France, May 1994, pp. 251–256
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A recording of a briefing on "The Role of Passive Radar Sensors for Air Traffic Control" at an IEE seminar from June 2006 can be seen here
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Howland, P.E.: "Target tracking using television-based bistatic radar", IEE Proc.-Radar, Sonar & Navig., Vol. 146, No. 3, June 1999.
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and hence cross-correlation yields a useful result. Some broadcast signals, such as analogue television, contain a structure in the
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Reception of the direct signal from the transmitter(s) and the surveillance region on dedicated low-noise, linear, digital receivers
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Association and fusion of line tracks from each transmitter to form the final estimate of an object's location, heading and speed.
1479:"Thales and EADS Defence & Security pool their technological and operational expertise in the promising passive radar market"
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has launched the first operational ground passive radar specifically designed to track LEO. The Oculus Observatory is based in
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standard is particularly good for passive radar, having an excellent ambiguity function and very high power transmitters. The
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Barott, William C.; Butka, Brian (2011). "A passive bistatic radar for detection of aircraft using spaceborne transmitters".
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Aeronautical University announced results claiming success using XM Radio to detect aircraft with a low-cost ground station.
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Radio Science 2003, v39, "Passive coherent scatter radar interferometer implementation, observations, and analysis"
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of the object to be determined. In addition to the bistatic range, a passive radar will typically also measure the
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Maverick-M passive radar for tactical surveillance and MAVERICK-S passive radar for surveillance of air and space.
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57:) – which is a broad type also including the exploitation of cooperative and non-cooperative radar transmitters.
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deployed a bistatic CW system called the RUS-1, and the Japanese developed a bistatic CW radar called "Type A".
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Nordwall B.D.: "Silent Sentry A New Type of Radar", Aviation Week & Space Technology, no 30, 1998, pp 70–71
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emissions). However, these systems do not exploit reflected energy and hence are more accurately described as
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Much current research is currently focusing on the exploitation of modern digital broadcast signals. The US
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980:
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863:). There is also active research on this technology in several governments or university laboratories in
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923:, have shown that it is possible to build a synthetic aperture image of an aircraft target using passive
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A recording of the 2004 Watson-Watt Lecture at the UK Institution of Electrical Engineers (IEE) can be
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The above description assumes that the waveform of the transmitter being exploited possesses a usable
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of the reference channel with the surveillance channels to determine object bistatic range and Doppler
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to determine the direction of arrival of signals and spatial rejection of strong in-band interference
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A recording of a briefing on "PCL Radar Tracking" at an IEE seminar from June 2006 can be seen here
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radars as non-cooperative illuminators, to detect aircraft over the southern part of the North Sea.
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Researchers at Embry-Riddle claiming the use of XM-Radio to detect aircraft can be found here
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501:), but this is the exception rather than the rule, as the transmitter must normally be within
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Passive radar systems have been developed that exploit the following sources of illumination:
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the transmitted waveform. A passive radar typically employs the following processing steps:
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or even complete reconstruction of the reference signal from the received digital signal.
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Lower costs of operation and maintenance, due to the lack of transmitter and moving parts
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Physically small and hence easily deployed in places where conventional radars cannot be
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is typically used. Most false alarms are rejected during this stage of the processing.
437:. This allows the direction of arrival of echoes to be calculated using standard radar
1844:
1573:"Passive Radar - from concept to reality with local SMEs - Australian Defence Magazine"
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208:, or "Winkle". Winkle was deployed in the 1960s in response to the introduction of the
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Mercier, Steven; Bidon, Stéphanie; Roque, Damien; Enderli, Cyrille (22 June 2020).
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Bistatic radar systems gave way to monostatic systems with the development of the
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https://digital-library.theiet.org/content/journals/10.1049/iet-rsn.2019.0574
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to cancel any unwanted direct signal returns in the surveillance channel(s)
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1086:. Electromagnetics and Radar. Institution of Engineering and Technology.
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One of the largest and most complex passive radar systems was the UK's
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exception to this is the exploitation of satellite-based radar and
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of object returns in range/Doppler space, known as "line tracking"
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using a series of fixed, overlapping beams or more sophisticated
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can be used to remove the direct signal in a process similar to
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techniques to exploit a variety of broadcast signals and to use
1825:
FM radio passive radar using two ultra-low-cost RTLSDR dongles
944:
the full, unaliased Doppler Power Spectrum of the turbulence.
722:
Silentium Defence Maverick-M man-portable passive search radar
714:
Silentium Defence Maverick S-series air and space search radar
684:
Opponents of the technology cite the following disadvantages:
283:
144:
664:
Covert operation, including no need for frequency allocations
371:
These are described in greater detail in the sections below.
1187:"Silent Sentry's Passive Coherent Location (PCL) technology"
654:
Advocates of the technology cite the following advantages:
847:, University of Birmingham, University College London and
790:
Daronmont Technologies SECAR-P Passive Radar for Australia
1206:
2011 IEEE/AIAA 30th Digital Avionics Systems Conference
1175:
Bistatic Radar Cross Sections of Surfaces of Revolution
1239:"Comparison of Correlation-Based OFDM Radar Receivers"
794:
Several academic passive radar systems exist as well:
466:
unwanted structures in digital signals to improve the
1246:
IEEE Transactions on Aerospace and Electronic Systems
895:
result for passive radar is like multiple repeaters
299:
systems. In 2011, researchers Barott and Butka from
1080:Willis, N.J.; Griffiths, H.D.; Davis, M.E. (2007).
505:of the receiver to ensure good low-level coverage.
233:launch of the Silent Sentry system, that exploited
170:(CW) radar in a "fence" (or "barrier") system; the
139:demonstrated the principle of radar by detecting a
177:The Germans used a passive bistatic system during
1789:Simple example of passive radar using analogue TV
1151:An Introduction to Passive Radar, Second Edition
65:Conventional radar systems comprise a colocated
1449:"Aulos, the green radar - SL - Planet Inspired"
839:in The Netherlands, in the United Kingdom (at
513:The key processing step in a passive radar is
378:Generic passive radar signal processing scheme
143:bomber at a distance of 12 km using the
741:Silent Sentry - exploiting FM radio stations
8:
1154:. Artech House radar library. Artech House.
851:), France (including the government labs of
1534:"Taking passive radar to the global stage"
909:University of Illinois at Urbana–Champaign
608:(CW) component, however, such as a strong
105:systems. Well known examples include the
759:Homeland Alerter - FM radio-based system
373:
344:Transmitter-specific signal conditioning
1519:"Twinvis Passive Radar | HENSOLDT"
1072:
747:CELLDAR - exploiting GSM base stations
592:Narrow band and CW illumination sources
1337:: CS1 maint: archived copy as title (
1330:
670:Rapid updates, typically once a second
567:Track association and state estimation
425:Most passive radar systems use simple
278:Terrestrial High-definition television
237:and analogue television transmitters.
1148:Griffiths, H.D.; Baker, C.J. (2022).
7:
1641:"UW Radar Remote Sensing Laboratory"
1532:silentuimdefence (25 October 2019).
697:1D/2D operation, but possible use 2
691:Reliance on third-party illuminators
580:, such as the extended or unscented
551:(CFAR) algorithm is typically used.
531:are usually used, in particular for
1419:"CELLDAR™ - Cellphone Radar System"
1117:Bistatic Radar: Emerging Technology
948:Space Debris Detection and Tracking
16:Radar system that does not transmit
855:), Germany (including the labs at
90:improve the final track accuracy.
14:
890:digital TV standard (and related
787:Passive Surveillance ESM Tracker
455:Very Long Baseline Interferometry
315:to be used to achieve an optimal
701:systems for 3D (height + range).
217:the jammer, other radars in the
1493:"Passive Radar : HENSOLDT"
913:Georgia Institute of Technology
861:Warsaw University of Technology
829:Georgia Tech Research Institute
706:Commercial and academic systems
73:, which usually share a common
935:Ionospheric Turbulence Studies
1:
280:transmitters in North America
1779:Resources in other libraries
1577:www.australiandefence.com.au
730:Hensoldt TwInvis at ILA 2018
650:Advantages and disadvantages
509:Cross-correlation processing
963:Swan Reach, South Australia
433:elements and element-level
181:. This system, called the
1866:
1083:Advances in Bistatic Radar
951:
529:discrete Fourier transform
453:and similar in concept to
273:Digital video broadcasting
268:Digital audio broadcasting
99:Electronic Support Measure
1774:Resources in your library
1688:10.1109/TAES.2018.2848340
1266:10.1109/TAES.2020.3003704
1214:10.1109/dasc.2011.6095957
968:University of Strathclyde
549:constant false alarm rate
517:. This step acts as the
355:constant false alarm rate
226:digital signal processing
28:passive coherent location
1616:"UIUC Passive Radar ATR"
1012:Semi-active radar homing
941:University of Washington
821:University of Washington
694:Complexity of deployment
598:radar ambiguity function
468:radar ambiguity function
183:Klein Heidelberg Parasit
1732:10.1049/ip-rsn:20045077
1598:"Manastash Ridge Radar"
1453:www.planetinspired.info
1114:Cherniakov, M. (2008).
1047:Kolchuga passive sensor
775:multiband passive radar
678:anti-radiation missiles
409:systems which output a
1850:Aerial warfare tactics
1310:www.lockheedmartin.com
981:Anti-radiation missile
954:Space domain awareness
929:fast Fourier transform
915:, with the support of
833:University of Illinois
731:
723:
715:
658:Lower procurement cost
379:
87:bistatic Doppler shift
51:passive bistatic radar
998:Passive Radar Project
859:), Poland (including
799:Manastash Ridge Radar
729:
721:
713:
673:Difficulty of jamming
492:Manastash Ridge Radar
377:
317:signal-to-noise ratio
22:(also referred to as
1671:10.1029/2003RS002985
1620:www.ifp.illinois.edu
1319:on 27 September 2011
1193:on 18 February 2010.
1042:Signals intelligence
753:Aulos passive radar
485:active noise control
457:used in astronomy).
451:phase interferometry
447:adaptive beamforming
441:techniques, such as
241:Typical illuminators
141:Handley Page Heyford
36:passive covert radar
32:passive surveillance
1604:on 5 December 2002.
1399:on 30 December 2006
1258:2020ITAES..56.4796M
1062:ELINT passive radar
1037:Low-frequency radar
1032:VERA passive sensor
939:Researchers at the
907:Researchers at the
841:Roke Manor Research
619:analogue television
461:Signal conditioning
443:amplitude monopulse
421:Digital beamforming
1794:2006-10-26 at the
1499:on 14 January 2019
1052:HEMPAS-CCIAS Radar
757:Thales Air Systems
732:
724:
716:
639:multistatic radars
497:2002-12-05 at the
474:Adaptive filtering
380:
339:Adaptive filtering
137:Robert Watson-Watt
1760:Library resources
1538:Silentium Defence
1223:978-1-61284-798-6
1161:978-1-63081-841-8
1127:978-0-470-98574-8
1093:978-1-891121-48-7
991:Multistatic radar
959:Silentium Defence
925:multistatic radar
804:Alim radar system
779:Silentium Defence
578:non-linear filter
515:cross-correlation
348:Cross-correlation
288:GPS reflectometry
250:Analog television
230:cross-correlation
219:Linesman/Mediator
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1713:
1706:
1700:
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1690:
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1656:
1654:
1652:
1643:. Archived from
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1628:
1626:
1612:
1606:
1605:
1600:. Archived from
1594:
1588:
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1569:
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1562:
1555:
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1495:. Archived from
1489:
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1455:. Archived from
1445:
1439:
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1425:. Archived from
1415:
1409:
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1406:
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1395:. Archived from
1385:
1379:
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1368:
1362:. Archived from
1357:
1349:
1343:
1342:
1336:
1328:
1326:
1324:
1318:
1312:. Archived from
1307:
1299:
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1292:
1290:
1288:
1252:(6): 4796–4813.
1243:
1234:
1228:
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1201:
1195:
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1189:. Archived from
1183:
1177:
1172:
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1136:
1134:
1111:
1105:
1104:
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1100:
1077:
1027:Stealth aircraft
810:Current research
774:
543:Target detection
407:digital receiver
360:Association and
353:Detection using
187:Heidelberg-Gerät
166:used a bistatic
116:systems and the
38:) is a class of
1865:
1864:
1860:
1859:
1858:
1856:
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1830:
1829:
1796:Wayback Machine
1785:
1784:
1783:
1768:
1767:
1763:
1756:
1722:
1720:Further reading
1717:
1716:
1707:
1703:
1697:
1693:
1680:
1676:
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1650:
1648:
1647:on 2 April 2005
1639:
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1596:
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1500:
1491:
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1486:
1477:
1476:
1472:
1462:
1460:
1459:on 22 July 2013
1447:
1446:
1442:
1432:
1430:
1429:on 8 March 2006
1417:
1416:
1412:
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1400:
1387:
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1370:
1366:
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1316:
1305:
1303:"Archived copy"
1301:
1300:
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1128:
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1079:
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1069:
1002:Multilateration
977:
956:
950:
937:
905:
812:
768:
739:Lockheed-Martin
708:
652:
627:
606:continuous wave
594:
569:
557:
545:
511:
499:Wayback Machine
481:adaptive filter
476:
463:
423:
390:
388:Receiver system
385:
309:
297:satellite radio
243:
168:Continuous Wave
150:transmitter at
129:
63:
24:parasitic radar
17:
12:
11:
5:
1863:
1861:
1853:
1852:
1847:
1842:
1840:Passive radars
1832:
1831:
1828:
1827:
1822:
1817:
1811:
1805:
1798:
1782:
1781:
1776:
1770:
1769:
1758:
1757:
1755:
1754:External links
1752:
1751:
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1691:
1674:
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1632:
1607:
1589:
1564:
1550:
1524:
1510:
1484:
1481:. 27 May 2008.
1470:
1440:
1423:www.roke.co.uk
1410:
1393:www.roke.co.uk
1380:
1369:on 9 July 2011
1344:
1294:
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1024:
1019:
1014:
1009:
1004:
999:
993:
988:
986:Bistatic radar
983:
976:
973:
952:Main article:
949:
946:
936:
933:
921:NATO C3 Agency
904:
903:Target imaging
901:
857:Fraunhofer-FHR
837:NATO C3 Agency
811:
808:
807:
806:
801:
792:
791:
788:
782:
776:
760:
754:
748:
742:
707:
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695:
692:
689:
682:
681:
676:Resilience to
674:
671:
668:
665:
662:
659:
651:
648:
642:of precision (
631:radar equation
626:
623:
593:
590:
568:
565:
556:
553:
544:
541:
519:matched filter
510:
507:
475:
472:
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427:antenna arrays
422:
419:
389:
386:
384:
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369:
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351:
345:
342:
336:
329:
313:matched filter
308:
305:
292:
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281:
275:
270:
265:
262:Cellular phone
259:
253:
242:
239:
133:United Kingdom
128:
125:
103:anti-radiation
83:bistatic range
62:
59:
46:bistatic radar
15:
13:
10:
9:
6:
4:
3:
2:
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1765:Passive radar
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1007:Radar tracker
1005:
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603:
599:
591:
589:
585:
583:
582:Kalman filter
579:
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566:
564:
562:
561:Kalman filter
555:Line tracking
554:
552:
550:
542:
540:
538:
534:
530:
527:based on the
525:
524:Doppler shift
520:
516:
508:
506:
504:
503:line-of-sight
500:
496:
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488:
486:
482:
473:
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448:
444:
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429:with several
428:
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412:
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404:
400:
399:dynamic range
396:
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357:(CFAR) scheme
356:
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318:
314:
306:
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264:base stations
263:
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41:
37:
33:
29:
25:
21:
20:Passive radar
1764:
1704:
1694:
1677:
1661:
1649:. Retrieved
1645:the original
1635:
1623:. Retrieved
1619:
1610:
1602:the original
1592:
1582:14 September
1580:. Retrieved
1576:
1567:
1553:
1541:. Retrieved
1537:
1527:
1513:
1501:. Retrieved
1497:the original
1487:
1473:
1461:. Retrieved
1457:the original
1452:
1443:
1431:. Retrieved
1427:the original
1422:
1413:
1401:. Retrieved
1397:the original
1392:
1383:
1371:. Retrieved
1364:the original
1360:www.dtic.mil
1359:
1347:
1321:. Retrieved
1314:the original
1309:
1297:
1285:. Retrieved
1249:
1245:
1232:
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1191:the original
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1170:
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1143:
1131:. Retrieved
1116:
1109:
1097:. Retrieved
1082:
1075:
957:
938:
906:
881:
877:South Africa
825:Georgia Tech
813:
793:
733:
698:
683:
653:
635:
628:
610:carrier tone
595:
586:
570:
558:
546:
512:
489:
477:
464:
435:digitisation
424:
395:noise figure
391:
370:
310:
301:Embry-Riddle
293:
286:satellites (
244:
223:
214:radar jammer
203:
195:
179:World War II
176:
172:Soviet Union
162:system; the
156:
130:
92:
79:
64:
61:Introduction
54:
50:
44:
35:
31:
27:
23:
19:
18:
1625:21 December
1287:13 December
1022:YLC-2 Radar
849:BAE Systems
785:ERA VERA-NG
769: [
745:BAE Systems
625:Performance
602:time domain
439:beamforming
333:beamforming
210:carcinotron
135:in 1935 by
95:transponder
81:allows the
67:transmitter
1834:Categories
1503:14 January
1133:18 January
1099:18 January
1067:References
1017:P-18 radar
835:), in the
688:Immaturity
383:Processing
191:Chain Home
160:CHAIN HOME
1559:"Vera-Ng"
1282:226415985
1274:0018-9251
1120:. Wiley.
1060:EL/L-8388
996:GNU Radio
699:different
614:estimator
411:digitized
403:linearity
401:and high
307:Principle
148:shortwave
118:Ukrainian
1792:Archived
1699:Kingdom.
1651:19 April
1333:cite web
1208:. IEEE.
975:See also
831:and the
817:Raytheon
763:Hensoldt
751:Selex ES
495:Archived
417:signal.
362:tracking
331:Digital
256:FM radio
235:FM radio
198:duplexer
152:Daventry
123:system.
121:Kolchuga
71:receiver
1389:"Radar"
1353:"ALERT"
1254:Bibcode
897:jammers
845:QinetiQ
766:TwInvis
574:ellipse
431:antenna
415:sampled
397:, high
258:signals
252:signals
206:RX12874
127:History
75:antenna
1762:about
1543:19 May
1463:22 May
1433:22 May
1403:22 May
1373:22 May
1323:22 May
1280:
1272:
1220:
1158:
1124:
1090:
873:Russia
322:sample
164:French
110:TAMARA
34:, and
1845:Radar
1367:(PDF)
1356:(PDF)
1317:(PDF)
1306:(PDF)
1278:S2CID
1242:(PDF)
917:DARPA
888:DVB-T
865:China
853:ONERA
773:]
107:Czech
40:radar
1802:seen
1749:2007
1736:2003
1682:2019
1653:2005
1627:2023
1584:2021
1545:2021
1505:2019
1465:2022
1435:2022
1405:2022
1375:2022
1339:link
1325:2022
1289:2020
1270:ISSN
1218:ISBN
1156:ISBN
1135:2023
1122:ISBN
1101:2023
1088:ISBN
1057:Elta
919:and
911:and
884:HDTV
875:and
869:Iran
644:GDOP
533:OFDM
212:, a
114:VERA
112:and
69:and
1684:doi
1667:doi
1262:doi
1210:doi
892:DAB
646:).
284:GPS
185:or
145:BBC
101:or
55:PBR
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