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Frequency sharing in Radiolocation bands

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Presentation on theme: "Frequency sharing in Radiolocation bands"— Presentation transcript:

0 Modern Architectures for Radiolocation Radars Abraham van den Berg Geneva, September 24th 2005
Air Systems Division

1 Frequency sharing in Radiolocation bands
PUBLIC Agenda Frequency sharing in Radiolocation bands Operational System Requirements Radar Modes and Architectures Air Systems Division

2 Frequency sharing in Radiolocation bands
PUBLIC Frequency sharing in Radiolocation bands Air Systems Division

3 Frequency Sharing in Radiolocation Bands
GPS IMT-2000 WAS ENG/OB TELEMETRY RLANs L-band: (1215 – 1400 MHz) RNSS: GPS, Glonass, Galileo S-band: (2700 – 3600 MHz) MS: ENG/OB, Future IMT-2000 Aeronautical Telemetry C-band: (5250 – 5850 MHz) MS: WAS, RLANs Air Systems Division

4 Operational System Requirements
Air Systems Division

5 Operational System Requirements
Mission statements and requirements for a clear environment Requirements for an EM polluted environment Future radar requirements. Air Systems Division

6 L-band Requirements (1)
Mission: Long Range Air Defence Long range detection of conventional aircraft (RCS > 2 m2) Medium range detection of latest generation ‘stealth’ air targets, i.e. missiles (RCS < 0.1 m2) High performance w.r.t. Electronic Counter-Counter Measures Guidance support for patrol aircraft Surface surveillance up to the radar horizon. Air Systems Division

7 L-band Requirements (2)
Mission: Volume Search by means of Multibeam Surveillance Fast 3D scanning with gapless elevation coverage up to 70º Excellent angular accuracy in elevation (< 1º) Improved detection at low elevation (reduction of multipath effect) Increased resistance against jamming and other interferences Jamming detection Improved operation in bad weather conditions Suppression of sea and land clutter Improved surface surveillance. Air Systems Division

8 L-band Requirements (3)
An example of a naval Volume Search Radar Air Systems Division

9 L-band Requirements (4)
L-band Requirements, highlights Increasing number of spot frequencies in agile mode (Interoperability, Multipath) Increasing system bandwidth (Detection of stealth targets, Multipath, ECM) Digital beamforming for 3D scanning radars Frequency diversity for ATC. Air Systems Division

10 S-band Requirements (1)
Mission: Military Air Traffic Control Civil ATC Radar modified for military application, i.e with additional environmental constraints Capability of countering chaff, deception and noise jamming. Mission: Battlefield and Border Surveillance 2D Detection and tracking of moving targets over a local area Required to rapidly alert a co-located tracking sensor Detection in land and weather clutter Air and surface targets. Air Systems Division

11 S-band Requirements (2)
Mission: Naval Surveillance Two-dimensional 2D primary surveillance and target indication Air as well as surface targets Suppression of sea clutter. Three-dimensional (3D Single Beam) Additional facility of measuring target altitude. Three-dimensional (3D Multi-beam) Multiple simultaneous beams to shorten reaction time. Air Systems Division

12 S-band Requirements (3)
Mission: Naval Multifunction Radar Surveillance and tracking in angle, range and velocity of multiple targets Phased array technology (Active as well as passive) Own missile guidance Kill assessment. Mission: Airborne Early Warning Long range and very long range (BTH) surveillance Target altitude determination All weather operation. Air Systems Division

13 S-band Requirements (4)
An example of a naval Multifunction Radar Air Systems Division

14 S-band Requirements (5)
S-band Requirements, highlights Increasing pulse bandwidth (Higher range resolution, NCTR) Trend toward higher duty cycles Increasing number of spot frequencies in agile mode (Interoperability, Multipath) Increasing system bandwidth (Detection of stealth targets, Multipath, ECM) Frequency diversity, up to 4 frequencies (ATC). Air Systems Division

15 C-band Requirements (1)
Mission: Naval Surveillance (2D and 3D) Same as in S-band, but with shorter range, 30 km km. Mission: Instrumentation Tracking On test ranges: Very accurate tracking of space and aeronautic vehicles undergoing developmental and operational testing Large parabolic reflector antennas and high EIRP Autotracking antennas, either on the skin echo or on a beacon. Air Systems Division

16 C-band Requirements (2)
Mission: Battlefield Weapon Locator Required to locate position of enemy fire and impact location Rapid horizontal scan in search mode Rapid horizontal and vertical scan in tracking mode Very agile, both in frequency and beam position Extremely sensitive, due to targets with very small RCS. Air Systems Division

17 C-band Requirements (3)
C-band Requirements, highlights Frequency agility over a wide system bandwidth Pulse bandwidth increases for high range resolution needs More and more 3D radars with fast beam agility Commonalitie with S-band radars, usually with shorter range Specificity: Very sensitive long range instrumentation radar. Air Systems Division

18 Requirements in an EM Polluted Environment
Inter-system electromagnetic compatibility Essentially compatibility with other radars in the same band No known requirements to share with communication systems Most of the time radars are protected by a primary status When co-primary, other systems are required to avoid harmful interference to radars. Electronic protection (or ECCM) requirements Chaff, noise jamming, false target generation, deception These requirements include: Frequency hopping and automatic tuning Advanced antenna design, combined with advanced signal and data processing. Air Systems Division

19 Future Requirements (1)
Tactical Ballistic Missile Defence (TBMD) Detection and tracking of ballistic missiles Cueing of other sensors Will require a mix of sensors at different frequencies. Air Systems Division

20 Future Requirements (2)
Low Probability of Intercept (LPI) No detection from ESM, jammer receivers, ARM receivers (even with a sensitity better than –80 dBm LPI can only be realized by diluting emissions (Low EIRP) In time: Increased duty cycle, CW In space: Wide transmitted beam and digital beamforming In frequency: Multi channel concepts. Stealth Targets Improved detection and tracking performance for targets with low RCS Will require high EIRP and large bandwidth Might require multi static modes Air Systems Division

21 Future Requirements (3)
Multifunction Surveillance radar, Fire control radar, Terrestrial comms, Satellite comms, ESM, ECM Benefits claimed for functional integration: Common antenna system at optimum location Increased flexibility in hardware allocation Increased electromagnetic compatibility Reduced radar signature Reduced number of antennas Reduction / elimination of electromagnetic blockage Reduced handover time between functions. Air Systems Division

22 Future Requirements (4)
Non Cooperative Target Recognition (NCTR) High resolution range profiling (< 1 m resolution) Short pulses and thus large bandwidth wave forms Jet Engine Modulation (JEM) Emissions at shorter wavelength High sample rate / high PRF for unambiguous spectrum Good close in phase noise performance Other techniques Polarimetry Multi static radar Air Systems Division

23 Radar Modes and Architectures
Air Systems Division

24 Radar Modes and Architectures (1)
Major Choices on Waveforms Classical Main design issues for the selection of waveforms Range resolution, accuracy and ambiguity Doppler resolution, accuracy and ambiguity Clutter cancelling Multi target performance Narrow band pulse Doppler waveforms Variety of parameters in frequency, pulse width and PRI Air Systems Division

25 Radar Modes and Architectures (2)
Major Choices on Waveforms Non classical FM-CW waveforms Passive radar Use of transmission of opportunity to perform radar functions High range resolution Target separation, isolation of target points for NCTR purposes, improved detectability in clutter Short pulse, pulse compression, deramp or stretched waveform, step frequency Air Systems Division

26 Radar Modes and Architectures (3)
Major Choices on Transmitted Power Compromise between peak power and duty cycle Influenced by transmitter technology. Transmitted RF pulses have to contain sufficient energy to: Detect a target with specified RCS at a specified range Overcome environmental noise effects Overcome path losses Overcome system losses Overcome man made noise sources Air Systems Division

27 Radar Modes and Architectures (4)
Major Choices on Receiver Selectivity RF filtering on multi frequency radars offers no rejection of in band interference IF filters, though effective, are not ideal and therefore offer only limited protection to interferers on nearby frequencies IF filter design has to balance in band performance against out of band rejection Traditionally filters have been designed to meet radar requirements and are thus not optimized for the rejection of communication signals Digital techniques may give the compensation for some IF filter limitations Air Systems Division

28 Radar Modes and Architectures (5)
Major Choices on Beamwidth Radar antennas are designed to concentrate RF energy in the wanted direction and suppress radiation in other directions Choice of beamwidth is related to: Requirements on detection range (power aperture product) Compromise between average power and antenna gain Requirements on angular resolution and accuracy Air Systems Division

29 Radar Modes and Architectures (6)
Techniques Facilitating Sharing (1/4) Receivers with high dynamic range Minimize the chance of unwanted intermodulation products being generated by interfering signals Reduce the risk of receiver saturation Analogue-Digital converters currently set the limits of achievable dynamic range, regardless of the receiver There is no advantage in the detection of small targets in the presence of low level interference Main beam sector blanking Protect other RF receivers in specific direction When applied in networked radars, complete volume coverage can be conserved Air Systems Division

30 Radar Modes and Architectures (7)
Techniques Facilitating Sharing (2/4) Narrowing of the beam Minimize the width of the transmitted beam of an array antenna Improves the received signal level Drawback is an increase in update time Long pulses Longer pulses allows a reduction in peak power Range resolution requirements dictate the use of pulse coding to maintain bandwidth Short range performance requirements often dictate the use of additional short pulses, thus increasing spectrum usage Air Systems Division

31 Radar Modes and Architectures (8)
Techniques Facilitating Sharing (3/4) Look back Reduction of false detections due to interference Can only be applied with phased arrays Coverage may degrade when the number of interference sources increases. Spread spectrum techniques Application of conventional DSSS techniques are equivalent to phase coded pulse compression techniques. Multi-user CDMA detection techniques could possibly be applied to improve interference suppression Drawback of multi-user detection is as a minimum an increase in the processing load and the complexity of the required hardware. Air Systems Division

32 Radar Modes and Architectures (9)
Techniques Facilitating Sharing (4/4) Frequency planning Possible when the interference exhibits a certain regularity Consultation between users of the frequency band can lead to frequency coordination FMCW mode Improved selectivity in comparison with pulse radars CW interference in the instantaneous radar band will cause desensitization Air Systems Division

33 Radar Modes and Architectures (10)
Radar Modes toward full Mitigation To achieve optimised mitigation, it is required that cooperative arrangements are made between users of the band. Two modes can be used: Radar modes for frequency division Determine bandwidth of sub-bands required for different users Divide sub-bands with sufficient frequency separation Allocation of a set of sub-bands spread over the available frequency range will be required Radar modes for spatial division Determine spatial sections to radiate Separate spatial areas by a safety margin Air Systems Division

34 Radar Modes and Architectures (11)
Radar Modes toward partial Mitigation Burn through mode: Improved S/(N+I) at the expense of update rate Frequency control mode: Does not work for unstable spectrum (frequency hopping transmitters) or when the whole band is occupied Sidelobe control mode: Complex technique that can only be applied for a limited number of interference sources Interference suppression mode: Improve resistance against interference at the expense of an increased system complexity and reduction in performance Air Systems Division

35 Thank you for your attention !
Air Systems Division

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