rfi2010, march 29-31 2010 groningen r. ambrosini et al. 1 roberto ambrosini ira-inaf...
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RFI2010, March 29-31 2010 Groningen
R. Ambrosini et al. 1
Roberto AmbrosiniIRA-INAF
“Old” hints to mitigators from the latest RFI experiences
Claudio Bortolotti,Mauro Roma,
IRA - INAF
Pietro Bolli,F. Messina,
F. GaudimonteOAC – INAF
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Content:
• From Analog to Digital modulationFrom Analog to Digital modulation• Regulatory aspects in Italy about the Regulatory aspects in Italy about the
installation an Eolic park close to SRT installation an Eolic park close to SRT (Sardinia Radio Telescope: 64m dish, 100GHz).(Sardinia Radio Telescope: 64m dish, 100GHz).
• Some operational considerations
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Tricks to fill the “60dB gap”Tricks to fill the “60dB gap”
• RA-769 levels are reachable only within RA-769 levels are reachable only within radio astronomical observations.radio astronomical observations.
Typical monitoring surveys are less sensitive (-60 dB typ).
To fill the gap in S/N, it is common to use in front of a spectrum analyzer:
• high gain antennas;• low noise preamplifiers (filtered);• a mobile van, to reduce the distance from the
interferer source or getting it within line of sight, • shrink the bandwidth around the Analog carriers
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How the digital spectrum appears now (1)
• No more narrowband carriers…….No more narrowband carriers…….– reduced sensitivity detection:
• S/N does not depend on measuring Bandwidth;• average levels are intrinsically lower (/channel);
• spectra are very similar to the radioastronomical observable;
• Consequences:Consequences:– On monitoringmonitoring:
• more difficult to reach ITU-769 levels;• antenna gain vs coverage tradeoff
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How the digital spectrum appears now (2)
• harder to discriminate among different interferers;• larger incidence of transienttransient interferers
(es. city buses, mobile wifi, etc)
• no simple identification of the interferer (coded ID)
– On receiver design:On receiver design:• the Rx dynamic range has to match the peak voltage and peak voltage and
total power total power applied to the active junctions;• we expect higher out of band emissions
(see the TV case)
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The TV case
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Analog TV
-60dB
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Digital TV
-60dB
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The SRT status
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Regulatory premiumRegulatory premium
• Even if narrowband, allocated bands (and in
particular the exclusive ones under 5.340) allow:– accurate calibrations of RA observations– reference benchmarks for the experimental verification of
mitigation techniques
– we can use them as a real deterrent against interferers (like wind turbines)
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The wind turbine case for SRT
The Italian Administration is our legal referee in a confrontation case with any interferer, so we have first asked their assistance in all future contacts with the counterparts.
Art. 97 of the Unique Text of the General Code for Communication says: – 1 - “Whoever makes activities that, in any way,
produce a damage to a communication service, is punishable under the Penal Code…….
– 2 – “Assured the above, it is prohibited to jam or produce interferences to a communication service….
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Some operational considerations
• We have recently defined a feedback form to be filled by the Observing Scientist
• We ask for specific RFI events and Data Loss (justifying for example some extra observing time)
Finally….. please consider:Finally….. please consider:
Common Human Brain Speed Common Human Brain Speed vs vs
Wireless Bandwidth….Wireless Bandwidth….