RF Noise and Radio-Astronomy
A Brief History of Radio Astronomy
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1860's Maxwell develops
equations that govern
electromagnetic (EM) waves.
1860's-1930's physicists
suspect celestial bodies to emit
EM waves of non-visible
wavelength.
1930's Karl Jansky discovered
interference patterns in voice
communications.
A Brief History of Radio Astronomy
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1933 Through investigation and
consultation he was able to
track the source of interference
to the center of our galaxy.
1933-present This discovery
inspired other scientists and
engineers to come together to
design and build radio
telescopes.
What is Radio Astronomy
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The sub-category of the natural science
Astronomy concerned with Radio Frequency
emanation from celestial bodies.
Why is Radio Astronomy Important
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A Paramount tool for:
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Discovery
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Science
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Curiosity
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Explanation
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Many important scientific
discoveries have been proven
by the use of radio astronomy.
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The Big Bang
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Cosmic microwave background radiation
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New planets and galaxies
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Radio galaxies, quasars, pulsars, masers
Listening and Broadcasting
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“listening to space” The
principle is simple.
Implementation is not
Radio signals picked up by
antennae are converted into
audio signals.
These audio signals can be
analyzed to tell us more about
space.
How Radio Astronomy is
Implemented
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An “image” of radio space is
acquired by scanning space
with an antenna.
The antenna will pick up the
emanations very similar to
wireless communications.
The data that is read in is
sorted by frequency and shifted
to a visible wavelength.
How Radio Astronomy is
Implemented
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Scanning an area will give us
an image of the area.
Astronomers require an
extremely large signal to noise
ratio to produce a valuable
image or audio signal.
The Problem
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The frequencies of interest to
Radio Astronomers correspond
to frequencies RF engineers
use for communications.
The man-made radio emissions
are intercepted by the radio
astronomers.
This corrupts the astronomers
data leading to inaccuracies in
observations and
interpretations.
A Contemporary Concern
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In January 2012 the World Radio-communication
Conference's topic was interfering with radio astronomy
The relationship between radio astronomer and RF
engineer once a great partnership has now grown tense.
Allocation
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Frequencies that are chosen for allocation are
specially chosen for radio astronomy.
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The frequencies allocated to radio astronomy:
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608 – 614 MHz,
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1406,
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1420 – 1666 MHz,
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23, 33, 41, 61, 94 GHz
Much is Already Lost
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RF ranges have encroached
deeply into the observable
frequencies.
The 71-275 GHz portion of the
radio spectrum is the portion
that is in danger
Much of the 3-30 GHz range
has already been lost to the
widespread use of radar,
satellite communications, and
wireless telecommunications.
Communication Equipment
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Examples of equipment that
compete for radio astronomy:
UAS – unmanned aircraft services need
50MHz of useful spectrum
Satellite Down links – Iridium satellite system,
GLONASS
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Spectroscopy
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Imaging
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radar
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Other communication devices (short distance,
high power)
Communication Equipment
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Spill over from communication
is also a prominent problem
The equipment in place is
designed to operate in it's
allocated range.
The equipment “spills” over into
the radio astronomy range.
Enforcement
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There is no agreement on how
this issue should be addressed
The regulatory groups are not
sure if it should be dealt with by
a universal regulatory body or a
case by case basis.
There are regulatory measures
in place to protect astronomers
but they are rarely enforced.
The Problem Revisited
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The spectral range that is used
in radio astronomy is as of yet
largely unexplored and
somewhat unclaimed, but as
technology progresses other
uses for these frequencies are
being discovered.
The RAS and EESS are
becoming more and more
concerned.
The Solution
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There is no easy solution to this
problem.
Radio astronomy is of
paramount importance in
contributing to our
understanding of the universe.
Our expanding need for better
communications requires more
and more bandwidth.
Some temporary solutions have
been implemented and are as
follows.
Radio Interferometry
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To combat the signal to noise
ratio problem radio
interferometry has been
developed.
Interferometry is using arrays of
antennas to produce multiple
sets of data and filter out the
noise.
The problem: a very expensive
solution as many antennae are
needed, and it is still subject to
noise.
High Selectivity Antennae
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This poor solution works on a
very basic principle.
If we examine only a small
portion of the sky we can
eliminate much of the radio
noise picked up.
The problem: we lose much of
the important information as
well.
Satellite Radio Astronomy
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Best results in removing noise
from the signal is to remove the
antenna from the noise.
By putting the antenna in far
orbit astronomers hope to
eliminate all man made noise
from the equation.
The problem: This is a very
expensive solution. Space has
become cluttered with
communications satellites and
“space garbage” leaving little
room for radioastronomical
satellites.
Stewardship
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Conclusions Drawn:
There is no good solution as of
now for protecting radio
astronomy from
communications equipment
We as engineers must act as
stewards of science when
designing communications
equipment.
Questions