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RFI2010 - RFI Mitigation Workshop 29 - 31 March, 2010, Groningen (NL)
The RFI monitoring systems for the Medicina and the Sardinia Radio
Telescope
R. Ambrosini (IRA), P. Bolli (OAC), C. Bortolotti (IRA), F. Gaudiomonte (OAC), F. Messina (OAC), M. Roma
(IRA)
Osservatorio Astronomico di Cagliari
Istituto di RadioastronomiaSezione di Medicina
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Agenda• The Italian radio telescopes;
• Update of the SRT’s construction;
• The RFI monitoring systems of Medicina and SRT:
• Fixed station;• Mobile station;
• Recent activity of the RFI group: (i) faraday room, (ii) wind farm, and (iii) routine measurements.
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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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Materaoperato da ASI
Italian network
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• Fully steerable radio telescope for: Radio astronomy , Geodynamical studies, Deep Space Network, Single dish and VLBI
• 0.3-100 GHz continuous frequency coverage
• 64 m diameter primary mirror; 7.9 m diameter secondary mirror
• Gregorian configuration with Shaped Surfaces
• Active Surface: Primary mirror with 1116 actuators a) Compensate gravitational and thermal deformations b) Convert Shaped surface of the primary to a Parabolic surface for primary focus operation
• Six focal positions (up to 20 receivers): Primary, Gregorian, Four Beam Wave Guide
• Primary surface accuracy: 150 um RMS
• Pointing accuracy (RMS): 2 ÷ 5 arcsec
SRT Technical Specifications
5/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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RA receivers for the first lightFrequency band Note
305 – 410 MHz Primary, dual frequency
1.3 – 1.8 GHz Primary, dual frequency
5.7 – 7.7 GHz BWG, mono-feed
18 – 26 GHz Gregorian, multi-feed
6/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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RFI campaigns in SardiniaRFI Campaign
Goals
October 1992
RFI monitoring across South and Center Sardinia
May 1996 RFI monitoring in Gerrei area
November 1997
RFI monitoring in Gennargentu area
October 2002
RFI characterization of the site chosen to host SRT
June 2004 RFI measurement in the frequency bands of the first light receivers
April 2007 Joined campaign with RFI mobile laboratory and fixed station installed at the site
7/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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Features of SRT siteThe SRT site is located 35 Km North of Cagliari (700 m asl).
Latitude: 39d 29m 50s NLongitude: 9d 14m 40s E
1.The site is well shielded by mountains sorrounding the radio telescope.
2.The area is far away from populated centers.
8/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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SRT updateHigh level meeting between INAF and Communication
Department of the Government are underway.
Full support from National Administration.
9/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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1. …. monitoring the frequency bands allocated by ITU to RAS. If man-made signals interfere with the radio astronomical observations, an official claim must be reported to the National Administration asking for protection.
2. …. monitoring also the out-of-RAS bands used by astronomers to observe the sky. The RFI information can improve the design of microwave receivers, the strategies of scientific observation, and the mitigation techniques.
RFI monitoring system: goals
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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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RFI monitoring system: schemeA fixed station with antennas placed on a
tower close to the radio telescope
A mobile laboratory to move closer to the
RFI transmitter
(i) receive the interference, (ii) collect as many data as possible of the RFI, (iii) identify the content of the signal, (iv) and detect the exact position of the transmitter (triangulation).
(i) good sensitivity, (ii) high compression point, (iii) wide frequency bands, (iv) automatically (24 h / day) and remotely controlled.
11/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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Fixed RFI station: scheme
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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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Microwave front-end
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Fixed RFI station: comparisonFeatures Medicina SRT (current version)
Tower height 25 m 12 m
Max frequency
2.4 GHz 3 GHz
Antennas 2 LPDA (80 – 500 MHz)2 LPDA (500 – 1000 MHz )2 dual pol. Yagi (320 – 332 MHz)2 dual pol. Yagi (400 – 416 MHz )2 dual pol. Yagi (606 – 612 MHz )1 reflector 1.2 m pol. 45° (1.3 – 2.4 GHz )
1 LPDA (0.3 – 5 GHz)1 LPDA (1.2 – 2.5 GHz)
Rotor 1 axis for azimuth direction 2 axis for: azimuth direction and polarization
Lenght & type of coaxial cable
35 m LCF ½” Cu2Y CELLFLEX (max 3 GHz)
55 m of FSJ4-50B Andrew (max 10 GHz)
Spectrum Analyzer
AGILENT 8562EC HP 8594
Receiver ICOM R9000 ICOM R9500
>25 m
18 GHz
Optical fiber link
Satellite monitoring
1 Az-El reflector 1.5 m pol. 45° (1.1 – 12 GHz)
Not yet available
PSA 4446E
14/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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RFI towersMEDICINASRT
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RFI laboratories
MEDICINA
SRT
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Band Frequency band
Antenna gain
Chain gain
Noise figure
P
320 – 332 MHz 14 dBi 37 dB 3 dB (300 K)
400 – 416 MHz 15 dBi 36 dB 3 dB
606 – 612 MHz 16 dBi 32 dB 3 dB
L 1.29 – 1.73 GHz 20 dBi 34 dB 3.5 dB
S 2.20 – 2.34 GHz 23 dBi 33 dB 3.5 dB
Satellite monitor
1.1 – 12 GHz (AZ-EL)
19 dBi 12 dB 12 dB @ 10 GHz
Band Frequency band
Antenna gain
Chain gain
Noise figure
P295 – 428.5 MHz
6 dBi 28 dB 10.5 dB (3000K)
L 1.18 – 1.80 GHz 12.5 dBi 22.3 dB 10.0 dB
S 2.07 – 3.39 GHz 5.5 dBi 15.7 dB 13.0 dB
Fixed RFI station: performance
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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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Mobile RFI stations
MEDICINASRT
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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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SRT Mobile RFI station
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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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Features Medicina SRT
Van Fiat Ducato Mercedes Sprinter 315 CDI
Maximum seats 3 2
Max frequency 18 GHz (Normal operation) 40 GHz
18 GHz (Normal operation) 40 GHz
Antennas 1 LPDA (0.31 – 0.62 GHz)1 LPDA (0.1 – 1.3 GHz)1 LPDA (1.2 – 2.4 MHz)1 dual ridge horn (1 – 18 GHz) 1 horn (18 – 26.5 GHz)1 horn (26.5 – 40 GHz)
1 LPDA (0.3 – 0.6 GHz)1 LPDA (0.1 – 1.3 GHz)1 dual ridge horn (1 – 18 GHz)1 dual ridge horn (18 – 40 GHz)
Telescope pole height
11 m 11 m
Telescope movement
Up/down servo Azimuth manualPolarization manual (standard 45°)
Up/down servo Azimuth servo or manualPolarization servo
Equipped SA SA HP 8562A (up to 26.5 GHz) PSA 4446 E (up to 44 GHz)
Other characteristics
Laboratory + storehouse; anti-shock rack; self powered (auxiliary batteries / AC 220 V); GPS
Mobile RFI station: comparison
20/26
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2010,
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Band Frequency band Antenna gain
Chain gain Noise figure
P300 – 434 MHz 5.5 dBi 32 dB 6 dB
604 – 611 MHz 5.5 dBi 29 dB 9.5 dB
L/S 1.22 – 2.45 GHz 4 or 9 dBi 32 dB 4.5 dB
S 2.45 – 4 GHz 4.5 dBi 26dB 5 dB
C 4 – 8 GHz 5 dBi 28 dB 4.5 dB
X 8 – 12 GHz 6 dBi 49 dB 5 dB
Ku 12 – 18 GHz 8 dBi 37 dB 8.5 dB
K 18 - 26.5 GHz 21 dBi 56 dB 3.1 dB
Ka 26.5 – 40 GHz 21 dBi 50.5 dB 4 dB
Band Frequency band Antenna gain
Chain gain Noise figure
P 290 – 428 MHz 9 dBi 36.2 dB 3.8 dB
L 1.17 – 1.84 GHz 7 dBi 29.8 dB 4 dB
S 1.99 – 3.37 GHz 7.8 dBi 25 dB 5.3 dB
S / C 2.98 – 5.81 GHz 12 dBi 25 dB 5.5 dB
C / X 5.22 – 9.25 GHz 11.5 dBi TBD TBD
X / Ku 7.76 – 18 GHz 12.5 dBi TBD TBD
K / Ka 18 – 40 GHz TBD TBD TBD
Mobile RFI station: performance
21/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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RFI measurements were conducted to evaluate the emission of a super-computing facility (80 nodes with dual CPU dual core each) to be placed at SRT.
Goal of the measurement was to evaluate if the auto-interference are compatible with Rec. 769. If not, to identify the shielding level of a Faraday room to be installed at SRT station.
Faraday room at SRT site
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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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Faraday room at SRT site
The figures we got (especially at frequencies lower than 1 GHz) exceed by about 60 dB, the detrimental values suggested by ITU-R RA.769-2 as the ones representative for continuum and spectral line radio astronomy observations.
23/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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RFI campaign at a wind farmWind farm Monte Guzzini
(CA)
Number of turbins
26
Electrical power (maximum)
22 Mwatt (850 Kwatt each)
Modell of turbine
VESTAS V-52
Dimension of each turbine
Height of the mast 55 m, 3 blades with radius 26 m
Type of measurement
Primary emission (no reflection contribution)
24/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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RFI campaign at a wind farm
Very strong wide band impulsive signal mainly in P (350 MHz) and L (1.5 GHz) bands associated electrical discharges in the power station of the wind farm.
-85 dBW (0 dBi)
25/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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Routine RFI measurementsRoutine RFI measurements are conducted every week to monitor the band of interest for the first light of SRT.
Frequency [MHz]
External CW at 426 MHz
The P frequency band of the dual frequency receiver was reduced from 305-425 MHz to
305-410 MHz.
Two identical HTS microwave band-pass filters are underway in
collaboration with Prof. Lancaster and Dr. Huang (Univ. of
Birmingham)
26/26
P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope
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2010,
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Conclusions• SRT is very close to its inauguration;
• A team of local technicians has been trained to take care of the RFI problems;
• SRT is in progress to be equipped with state-of-the-art RF instrumentation for monitoring the RFI, following the thirty-year experience gathered at Medicina;
• The RFI activity consists both: (i) in routine measurements at the site, and (ii) in ad hoc campaign addressed to specific questions.