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

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

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

3. 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 Air Systems Division

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

5. 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 Air Systems Division

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

7. 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 • 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 (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 confidence What about radar ? Air Systems Division

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

9. 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 ? Air Systems Division

10. 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 Air Systems Division

11. 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 < -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” Air Systems Division

12. 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 Air Systems Division

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

14. « 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 Air Systems Division

15. « 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 Air Systems Division

16. 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 fixedfrequency 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 Air Systems Division

17. 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 Air Systems Division

18. 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 Air Systems Division

19. 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 Air Systems Division

20. 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 Air Systems Division

21. Some conclusive propositions Air Systems Division

22. 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 Air Systems Division

23. 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 Air Systems Division

24. Thank you for your attention Air Systems Division