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RF Noise and Radio-Astronomy. A Brief History of Radio Astronomy. 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.
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A Brief History of Radio Astronomy • 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 • 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 • The sub-category of the natural science Astronomy concerned with Radio Frequency emanation from celestial bodies.
Why is Radio Astronomy Important • A Paramount tool for: • Discovery • Science • Curiosity • Explanation • Many important scientific discoveries have been proven by the use of radio astronomy. • The Big Bang • Cosmic microwave background radiation • New planets and galaxies • Radio galaxies, quasars, pulsars, masers
Listening and Broadcasting • “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 • 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 • 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 • 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 • 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 • Frequencies that are chosen for allocation are specially chosen for radio astronomy. • The frequencies allocated to radio astronomy: • 608 – 614 MHz, • 1406, • 1420 – 1666 MHz, • 23, 33, 41, 61, 94 GHz
Much is Already Lost • 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 • Examples of equipment that compete for radio astronomy: • UAS – unmanned aircraft services need 50MHz of useful spectrum • Satellite Down links – Iridium satellite system, GLONASS • Spectroscopy • Imaging • radar • Other communication devices (short distance, high power)
Communication Equipment • 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 • 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 • 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 • 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 • 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 • 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 • 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 • 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.
