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