rfi2010 - rfi mitigation workshop 29 - 31 march, 2010, groningen (nl) the rfi monitoring systems for...

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

http://www.inaf.it/

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P. Bolli, The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope

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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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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

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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

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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

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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.

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SRT updateHigh level meeting between INAF and Communication

Department of the Government are underway.

Full support from National Administration.

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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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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.

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Fixed RFI station: scheme

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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

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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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Mobile RFI stations

MEDICINASRT

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SRT Mobile RFI station

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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

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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

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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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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.

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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)

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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)

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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)

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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.

rfi2010 - rfi mitigation workshop 29 - 31 march, 2010, groningen (nl) the rfi monitoring systems for...

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