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

Air Systems Division

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 antenna+transmitted 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 requirementOperational requirement : exhaustive, : exhaustive, continuous, reliable coverage for aircraft continuous, reliable coverage for aircraft

separation of 3, 5 or 10 MNseparation of 3, 5 or 10 MN

"En-route" Primary Radar “Approach” Primary RadarRange longer than 150 MN Range : from 0,5 MN to 60, 80 or 100 MN

Source : Eurocontrol

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Example : ATC radar

Operational Requirements Distance resolution < 150 m ; distance accuracy < 80 m Angular resolution < 1,5° ou 2,3° ; Angular accuracy < 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 > 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


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 ==> Interference detectionInterference 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 ==> Interference measurement & identificationInterference measurement & identification (even if subjective)

Is is not a harmful interference I have enough information & awareness to go on listening my radio ==> As an informed operator, I am a robust processor to get along

even with the obvious interference ==> My operational degradation is bearable in confidencedegradation is bearable in confidence

What about radar ?

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Way from interference to operational significance

DigitalWaveformGenerator

ClockFirstLocalOscillator

AgileLocalOscillator

Dup.B

eamform

er

Antenna

ADC

DigitalPhase SensitiveDetector

RF BandImage RejectionFilter

First IFBand PassFilter

Second IFBand PassFilter

HarmonicsFilter

High PowerAmplifier

Band PassFilter

Band PassFilter

LNA

DigitalBand PassFilter

I

Q

DisplayRange

Processing(DPC)

DopplerProcessing

(MTI/MTD)

Thresholding(CFAR)

PlotExtraction

Tracker

Signal Processor

Data Processor

Interference :Interference :I/N = f(d,,t,……)

Operations :Operations :

I/N « considerations » ?? GAP ??

Radar functional diagramRadar functional diagram

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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 saturationNo saturation of radar receivers Continuous noise interference : I/N < -6 dB I/N < -6 dB protection criterion Impulsive signal interference : specific studies

Real life in sharing cases : If saturation unambiguous harmful interference If I/N < -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

distant-channeldistant-channel I/N for fan beam

2D fan beam radar

3D pencil beam radar

Frequency

Radar agilitybandwidth

Radar instantaneousbandwidth

Co-channeloperating station

Adjacent channeloperating station

Adjacent bandoperating station

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« Proliferating » interferers

Distant-channel I/N = -6dB

Adjacent-channel I/N = -18dB

Co-channel I/N = 50 dB2D fan beam radar

3D pencil beam radarIn any case, operationally speaking, In any case, operationally speaking, unrecoverable cases :unrecoverable cases :

* 2D radar : ± degraded, eventually terminally

* 3D radar : ± degraded, but more « robust »

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0 200 400 600 800 1000 1200 1400-50

-40

-30

-20

-10

0

10

Temps (sec)

Rap

port

I/N

(dB

)

Rapport Interference a Bruit sur les satellites « Discrete » interferersInterference from satellite

Constellation to ATC radar Co-channelCo-channel ratio I/N

instantaneous probability of detection tracking probability

Worst case :Worst case : 10s delay in track-init = 2 scans

0 200 400 600 800 1000 1200 1400

0

0.2

0.4

0.6

0.8

1

Time (sec)

Pro

babi

lity

of d

etec

tion

Target instantaneous probability of detection

0 200 400 600 800 1000 1200 1400

0

0.2

0.4

0.6

0.8

1

Temps (sec)

Pro

babi

lite

de p

ista

ge

Probabilite de conserver une piste confirmee

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 DFS+TPC 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 fixedfixed frequencyfrequency radar, if a solution is found

Fast scale During transition periods, few radar bursts interfered with, leading to false

alarm, or with frequency agilefrequency 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

ANDANDOperational requirements have become more stringent Advanced radar techniques are mainly for :

More stringent known in advanced and specifiedknown in advanced and specified operational requirements lesser price for same performance

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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 => detectable interference, but leaves some

spectrum free wideband => low PFD => undetectable ? , but occupies more spectrum

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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


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


Thank you for your attention

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

Documents

radar emc radar

radar frequency

primary radar

radar emc requirements

new template

radar functional diagram

mitigating radiolocation

saturation of radar