Modern Architectures for Radiolocation Radars Abraham van den Berg Geneva, September 24th 2005 : Modern Architectures for Radiolocation Radars Abraham van den Berg Geneva, September 24th 2005
Agenda : Frequency sharing in Radiolocation bands
Operational System Requirements
Radar Modes and Architectures Agenda
Frequency sharing in Radiolocation bands : Frequency sharing in Radiolocation bands
Frequency Sharing in Radiolocation Bands : Frequency Sharing in Radiolocation Bands 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
Operational System Requirements : Operational System Requirements
Operational System Requirements : Operational System Requirements Operational System Requirements
Mission statements and requirements for a clear environment
Requirements for an EM polluted environment
Future radar requirements.
L-band Requirements (1) : 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.
L-band Requirements (2) : 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.
L-band Requirements (3) : L-band Requirements (3) An example of a naval Volume Search Radar
L-band Requirements (4) : 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.
S-band Requirements (1) : 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.
S-band Requirements (2) : 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.
S-band Requirements (3) : 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.
S-band Requirements (4) : S-band Requirements (4) An example of a naval Multifunction Radar
S-band Requirements (5) : 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).
C-band Requirements (1) : C-band Requirements (1) Mission: Naval Surveillance (2D and 3D)
Same as in S-band, but with shorter range, 30 km - 120 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.
C-band Requirements (2) : 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.
C-band Requirements (3) : 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.
Requirements in an EM Polluted Environment : 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.
Future Requirements (1) : 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.
Future Requirements (2) : 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
Future Requirements (3) : 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.
Future Requirements (4) : 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
Radar Modes and Architectures : Radar Modes and Architectures
Radar Modes and Architectures (1) : Radar Modes and Architectures (1) 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
Major Choices on Waveforms
Radar Modes and Architectures (2) : Radar Modes and Architectures (2) 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
Major Choices on Waveforms
Radar Modes and Architectures (3) : Radar Modes and Architectures (3) Compromise between peak power and duty cycle
Influenced by transmitter technology.
Major Choices on Transmitted Power 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
Radar Modes and Architectures (4) : Radar Modes and Architectures (4) RF filtering on multi frequency radars offers no rejection of in band interference Major Choices on Receiver Selectivity 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 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
Radar Modes and Architectures (5) : 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
Radar Modes and Architectures (6) : 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
Radar Modes and Architectures (7) : 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
Radar Modes and Architectures (8) : 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.
Radar Modes and Architectures (9) : 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
Radar Modes and Architectures (10) : Radar Modes and Architectures (10) Radar Modes toward full Mitigation 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 To achieve optimised mitigation, it is required that cooperative arrangements are made between users of the band. Two modes can be used:
Radar Modes and Architectures (11) : Radar Modes and Architectures (11) Burn through mode: Improved S/(N+I) at the expense of update rate Radar Modes toward partial Mitigation 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 Frequency control mode: Does not work for unstable spectrum (frequency hopping transmitters) or when the whole band is occupied
Thank you for your attention ! : Thank you for your attention !