Transcript PPT - Astron

RFI measurements at the WSRT
Hans van der Marel
ASTRON
RFI Mitigation workshop, Groningen, 29-31 March 2010
Introduction
• Astronomical observations
– Local or non-local interference
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Spectrum monitoring station
National Frequency allocation table
Test observations for less known bands
Investigations for local interference
Astronomical observations
Astronomical observations (2)
Spectrum monitoring station
• Current station operational since 2005
– Latest antenna modification December 2007
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Continuous coverage 20 - 3000 MHz
Scanning 24/7
Calibrated data
Data in RMDF format
Analysis program available
Data available to CRAF
Set-up of Monitor Station
R&S HF902
R&S HK309
Roof of construction hall
coax
coax
Construction hall
Antenna
switch
Control
cable
converter
coax
UTP
coax
R&S EB200
receiver
Field
Control
computer
Main building
Glass fiber
To ASTRON network
Rohde & Schwarz EB200 Miniport
receiver
• Frequency range 10 kHz - 3 GHz
• Noise floor -117 dBm @ 30 kHz BW
• Scan speed 126 points/s
 20 - 3000 MHz in 13.5 min @ 30 kHz BW
Rohde & Schwarz antennae
HK 309
HF 902
• Freq range: 20 - 1300 MHz
• Passive
• Linear polarization
• Freq range: 1 - 3 GHz
• Passive
• Linear Polarization (V used)
Schematic of Control Program
Measurement
module
Calibration
files
*.dat
Measurement
file
measure.dat
TCP/IP
connection
EB 200
measurement
receiver
GUI of Control Program
Header File (*.rmh)
Schematic of Analysis Program
Graphical Presentation (1)
Graphical Presentation (2)
Graphical Presentation (3)
Test observations (e.g. 608 MHz)
Investigations of local or internal
interference
• Usually in 1 or few telescopes
• Malfunctioning equipment
– E.g. oscillating amplifiers, leaking of LO
• Interfering equipment
– Computers, networks, lab equipment
Tools:
• Handheld antennas, probes, spectrum
analyzer, receiver
• Experience
Summary
• Astronomical observations are inspected,
they are the most sensitive
– Autoplots give first indication
– Reports from astronomers
• Spectrum monitoring station gives indication about
possible RFI
• Test observations can reveal real usability of
frequency band
• Good relation with National Agency is important
• Know your enemy (e.g. Galileo)
• Local and internal interference requires continuous
attention