ITU-R SG8 WP8B Radar Seminar : Factors to consider for Intersystem EMC (continued) Thierry JURAND Geneva, September 24th 2005

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ITU-R SG8 WP8B Radar Seminar Factors to
consider for Intersystem EMC (continued)Thierry
JURANDGeneva, September 24th 2005
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Agenda

• Operational Requirements Frequency Requirements
• The long way on characterisation from
  interference to operational significance
• Some conclusive propositions

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Radar and Frequency

• Radar Operational Requirements ..
• A summary of civil radar missions
• Detection
• Location
• Resolution
• Tracking
• Military radar may have additional requirements
• Classification
• Recognition
• Missile Communications
• Electronic Protection
• Lead to Radar Spectral requirements
• Choice of frequency band
• Choice of antennatransmitted power
• Instantaneous bandwidth
• Frequency diversity, eventually agility
• Compatibility with other radar EMC requirements

Allocated Radar Frequency is necessary
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Example ATC radar
Operational requirement exhaustive, continuous,
reliable coverage for aircraft separation of 3, 5
or 10 MN
Source Eurocontrol
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Example ATC radar

• Operational Requirements
• Distance resolution lt 150 m distance accuracy lt
  80 m
• Angular resolution lt 1,5 ou 2,3 Angular
  accuracy lt 0,15
• Speed coverage 40 à 800 knots (75 -1500km/h)
• Information renewal rate 5 à 6 rpm class or 12
  à 15 rpm class
• Spectral Requirements
• L-band, 1 215-1 350 MHz or S-band, 2 700-2 900
  MHz
• Instantaneous bandwidth 1 MHz
• Frequency diversity at least 2 channels
  separated by several tens MHz (bande S gt 35 MHz)
• Operating compatibility with other radar (9
  primary radar in France, excl. neighbouring
  countries)
• Compliance to emission control requirements (ITU,
  NTIA, MIL-STD)

Source Eurocontrol
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The long way on characterisation from
interference to operational significance
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Interference some operational considerations

• Cell Phone FM radio in your car Revisited
• Bips on your FM while your cell phone
  communicates with a base station
• Hey, I am undergoing interference
• gt Interference detection
• It violates an established or implicit protection
  criterion
• I may miss a long portion of a word or of a
  tune I know why
• gt Interference measurement identification
  (even if subjective)
• Is is not a harmful interference
• I have enough information awareness to go on
  listening my radio
• gt As an informed operator, I am a robust
  processor to get along even with the obvious
  interference
• gt My operational degradation is bearable in
  confidence

What about radar ?
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Way from interference to operational significance
Radar functional diagram
Interference I/N f(d,q,t,)
Operations
I/N  considerations 
?? GAP ??
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Interference main effects to radar

• Elementary
• Blocking
• Desensitisation
• False alarm
• System aspects
• Unrecoverable blinding jamming
• Loss of range overall coverage
• Track distortion, track losses false tracks
• Loss of accuracy
• Operational significance
• What is harmful interference ?

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Interference multidimensional aspects

• With respect to radar, Interference is a very
  wide world
• Strength dimension ? I/N
• Spatial distribution? I/N
• Signal structure
• From pure frequency wide multi-channel spread
  spectrum
• Temporal distribution
• Duty cycle ratio  on duration  over
   operating duration 
• Randomness
• Temporal scale
• Ultra fast scale few us, intra-pulse intra
  pulse-repetition-interval
• Fast scale few ms, radar burst or scan level
• Slow scale scan to scan
• Ultra slow scale

I/N analysis addresses few of these dimensions
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ITU intersystem EMC considerations

• ITU
• radars primary service in radionavigation,
  primary or secondary in radiolocation
• ITU radar protection
• No harmful interference when radar has precedence
  (e.g. primary)
• Recommendations
• No saturation of radar receivers
• Continuous noise interference I/N lt -6 dB
  protection criterion
• Impulsive signal interference specific studies
• Real life in sharing cases
• If saturation ? unambiguous harmful interference
• If I/N lt -6 dB tolerated interference, ?
  Unambiguously ? not harmful
• In between almost all cases under study at ITU
  ?
• Interference is never unambiguously continuous

Operational assessment of harmfulness is a wide
world
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Inter radar EMC

• Radar share well with each other
• directive and rotating transmissions
• pulsed transmissions,
• selective reception,
• false alarm processing
• tracking
• Recognised within the regulatory body .
• All the work pertaining and leading to the
  upgrade of radiolocation status from secondary to
  primary at WRC-03
• And operationally
• E.g. Maritime Navigation radar tests on
  mitigating radiolocation radar published in ITU
• E.g Several radars in the same band on close or
  even the same airport

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 Proliferating  interferers
2D fan beam radar
3D pencil beam radar
distant-channel I/N for fan beam
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 Proliferating  interferers
Distant-channel I/N -6dB Adjacent-channel I/N
-18dB Co-channel I/N 50 dB
2D fan beam radar
In any case, operationally speaking,
unrecoverable cases 2D radar degraded,
eventually terminally 3D radar degraded,
but more  robust 
3D pencil beam radar
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 Discrete  interferers

• Interference from satellite
• Constellation to ATC radar
• Co-channel ratio I/N
• instantaneous probability of detection
• tracking probability
• Worst case
• 10s delay in track-init 2 scans

Source WP8B/232 or WP8D/287 2000-3 study period
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RLAN in radar C band

• RLAN vs. Radar
• Radar in 5 250 5 850 MHz
• RLAN in 5 150 5 250 MHz 5 470 MHz 5 725 MHz
• Multi-channel spread spectrum discontinuous in
  time signal structure
• DFSTPC in radar bands as mitigation techniques
  for sharing
• Ultra-low scale scale
• Network establishment out of established
  neighbouring radar frequencies
• Slow scale
• Solve a conflict with fixed frequency radar, if a
  solution is found
• Fast scale
• During transition periods, few radar bursts
  interfered with, leading to false alarm, or with
  frequency agile radar
• Ultra fast scale
• Signals are in packets of duration comparable
  duration with radar pules
• RLAN intra-packet modulation may have non noise
  interaction with radar pulse modulation

C-band case might become a practical case study
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So where should one be ?

• The level of man made interference (unintentional
  jamming) is only acceptable when it does not
  reduce the performance of the radar below that
  required for fulfilling its mission
• The link between interference characterisation to
  operational significance is non universal and
  difficult to establish
• Other than conservative protection criteria
• It must be decided upon by the end user in
  consultation with the system designers
• Including the frequency management and regulatory
  process

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Constraints on the possibilities for sharing (1/3)

• Unavoidable consequences from operational
  requirements
• Radar power requirements
• operational requirements on range target RCS
• a compromise with waveform design (range energy
  average power)
• Radar instantaneous bandwidth requirements
• operational requirements on range resolution
• System bandwidth
• frequency diversity stems from operational
  requirements on coverage
• frequency agility stems from operational
  requirements on Electronic Protection
• ? There is no redundancy in radar transmission
• AND
• Operational requirements have become more
  stringent
• Advanced radar techniques are mainly for
• More stringent known in advanced and specified
  operational requirements
• lesser price for same performance

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Constraints on the possibilities for sharing (2/3)

• Economic considerations
• improved efficient filtering increases costs
• clean transmitter integration is expensive
• signal processing hardware low cost but more
  costs on the development side
• legacy radars
• Taking sharing as a requirement early in the
  design is cost effective
• Other than radar waveforms
• most of the time they induce noise like
  interference (desensitisation)
• But surprisingly enough not always ? false alarm
• bandwidth trade-off for sharing ?
• narrowband high PFD gt detectable interference,
  but leaves some spectrum free
• wideband gt low PFD gt undetectable ? , but
  occupies more spectrum

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Constraints on the possibilities for sharing (3/3)

• Communication systems proliferation
• Mobile services (phone, RLANs, etc.)
• increase in the number of terminals
• no unique technical analysis scenarios agreed
  upon in the regulatory body
• unstabilised business cases
• spread transmitters with quasi-omni directional
  antennas
• Establish better scenarios for refined studies,
  to be upgraded with market development
• Perform detailed specific studies
• Perform refined experimental tests

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Some conclusive propositions
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Conclusive propositions

• Radar performance will ALWAYS be degraded in the
  presence of interference.
• Mitigating against interference removes
  information or looses time
• Good Frequency planning will provide the best
  protection to radar systems
• Sharing with radar is a challenging problem, but
  there are some prospects, subjected to detailed
  study
• More with discrete than with proliferating
  interfering system
• Other than radar end customers and system
  designers need to include radar in the design and
  normalisation process early on
• Upgrade of the radiolocation service status to
  primary wherever it is secondary

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Conclusive propositions

• Development costs for new highly complex radar
  techniques could drive overall costs upwards
• Filtering and selectivity does provide useful
  protection to the radar
• Situation awareness will be a useful tool to
  minimise the amount of degradation
• Transmitter technology for radar
• tremendous effort and progress from Magnetron to
  Solid State
• It is inappropriate to impose too stringent
  regulatory constraints on radar transmissions
• Poor installation of communication systems often
  causes problems for their protection from radar

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Thank you for your attention