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

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

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

2 1 New template_march05 Air Systems Division Agenda Operational Requirements & Frequency Requirements The long way on characterisation from interference to operational significance Some conclusive propositions

3 2 New template_march05 Air Systems Division 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

4 3 New template_march05 Air Systems Division Example : ATC radar Operational requirement : exhaustive, continuous, reliable coverage for aircraft separation of 3, 5 or 10 MN Source : Eurocontrol

5 4 New template_march05 Air Systems Division 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

6 Air Systems Division The long way on characterisation from interference to operational significance

7 6 New template_march05 Air Systems Division 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 detection ==> 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 Interference measurement & identification ==> Interference 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 degradation is bearable in confidence ==> My operational degradation is bearable in confidence What about radar ?

8 7 New template_march05 Air Systems Division Way from interference to operational significance Interference : I/N = f(d,,t,……) Operations : I/N « considerations »?? GAP ?? Radar functional diagram

9 8 New template_march05 Air Systems Division 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 ?

10 9 New template_march05 Air Systems Division 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

11 10 New template_march05 Air Systems Division 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 No saturation of radar receivers I/N < -6 dB Continuous noise interference : 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

12 11 New template_march05 Air Systems Division 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

13 12 New template_march05 Air Systems Division « Proliferating » interferers distant-channel distant-channel I/N for fan beam 2D fan beam radar 3D pencil beam radar Frequency Radar agility bandwidth Radar instantaneous bandwidth Co-channel operating station Adjacent channel operating station Adjacent band operating station

14 13 New template_march05 Air Systems Division « Proliferating » interferers Distant-channel I/N = -6dB Adjacent-channel I/N = -18dB Co-channel I/N = 50 dB 2D fan beam radar 3D pencil beam radar In any case, operationally speaking, unrecoverable cases : * 2D radar : ± degraded, eventually terminally * 3D radar : ± degraded, but more « robust »

15 14 New template_march05 Air Systems Division « Discrete » interferers Interference from satellite Constellation to ATC radar Co-channel 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

16 15 New template_march05 Air Systems Division 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 fixedfrequency Solve a conflict with fixed frequency radar, if a solution is found Fast scale frequency agile 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

17 16 New template_march05 Air Systems Division 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

18 17 New template_march05 Air Systems Division 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 transmissionAND Operational requirements have become more stringent Advanced radar techniques are mainly for : known in advanced and specified More stringent known in advanced and specified operational requirements lesser price for same performance

19 18 New template_march05 Air Systems Division 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 => detectable interference, but leaves some spectrum free wideband => low PFD => undetectable ?, but occupies more spectrum

20 19 New template_march05 Air Systems Division 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

21 Air Systems Division Some conclusive propositions

22 21 New template_march05 Air Systems Division 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

23 22 New template_march05 Air Systems Division 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

24 Air Systems Division Thank you for your attention


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