SATELLITE COMMUNICATION BETT 4803 SEMESTER 1 SESI 2015/2016 LONG REPORT SIGNAL-TO-NOISE RATIO CALCULATION NAME SARAVANAN A/L SUKUMARAN MATRIX NUMBER B071210044 COURSE 4BETT DATE 25/12/2015 NAME OF INSTRUCTOR Mr. MOHD ANUAR BIN ADIP Mr. CHAIRULSYAH WASLI EXAMINER’S COMMENT(S) VERIFICATION STAMP TOTAL MARKS FAKULTI TEKNOLOGI KEJURUTERAAN UNIVERSITI TEKNIKAL MALAYSIA MELAKA
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SATELLITE COMMUNICATION
BETT 4803
SEMESTER 1
SESI 2015/2016
LONG REPORT
SIGNAL-TO-NOISE RATIO CALCULATION
NAME SARAVANAN A/L SUKUMARAN
MATRIX NUMBER B071210044
COURSE 4BETT
DATE 25/12/2015
NAME OF INSTRUCTOR
Mr. MOHD ANUAR BIN ADIP
Mr. CHAIRULSYAH WASLI
EXAMINER’S COMMENT(S)
VERIFICATION STAMP
TOTAL MARKS
FAKULTI TEKNOLOGI KEJURUTERAAN
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
1.0 OBJECTIVES
To understand the concept of the signal to noise ratio.
To calculate the signal to noise ratio of established satellite link.
2.0 EQUIPMENT
Hardware Type/Version Quantity
1. Uplink Transmitter Scientech ST 2272A 1
2. Downlink Receiver Scientech ST 2272A 1
3. Satellite Transponder Scientech ST 2272A 1
4. Dish Antenna Scientech ST 2272A 4
5. Oscilloscope 1
6. Spectrum Analyzer 1
3.0 SYNOPSIS & THEORY
Theory on Satellite Communication
Figure 3.1: Satellite in earth orbit
Satellites have been used for years for various purposes including scientific research, weather reporting,
communications, navigation and even for observing Earth. Engineers have played a key role in designing
these satellites, getting them into orbit, and using the information they relay back to Earth.
Communicating with people has always been an important part of human existence. As people live
further away from each other, and as they explore more and more remote regions, communication
with each other becomes even more important. An artificial satellite is a manufactured object that
orbits Earth or something else in space on a continual basis. Satellites are used to study the universe,
help forecast the weather, transfer telephone calls and assist in ship and aircraft navigation. Specifically,
communications satellites serve as relay stations, receiving radio signals from one location and
transmitting them to another. A communications satellite can relay several television programs or many
thousands of telephone calls at once. They essentially bounce messages from one part of the world to
another.
Figure 3.2 : Satellite Communication main components
Based on figure 3.2 above, Information is transmitted from a ground station (uplink) to the satellite,
converted to a different frequency and re-transmitted back to Earth (downlink). The downlink may
either be to a single ground station or the transmission may be broadcast to a large region via multiple
ground stations. The satellite must have a receiver with a receive antenna, a transmitter with a transmit
antenna, an amplifier and prime electrical power to run all of the electronics. The configuration of this
equipment will vary according to the satellite design but every communication satellite will have these
basic components. The effectiveness of a microwave antenna designed either to provide amplification
or beam the signal into defined regions of space is dependent on its size, which is in turn limited by
cost. By current calculations, doubling the antenna size will result in the satellite cost increasing eight
times.
Satellite Frequency Band
Figure 3.3 : Range of Satellite Frequency Bands
Based on figure 3.3 above, with the variety of satellite frequency bands that can be used, designations
have been developed so that they can be referred to easily. The higher frequency bands typically give
access to wider bandwidths, but are also more susceptible to signal degradation due to ‘rain fade’ (the
absorption of radio signals by atmospheric rain, snow or ice). Because of satellites’ increased use,
number and size, congestion has become a serious issue in the lower frequency bands. New
technologies are being investigated so that higher bands can be used.
L-Band (1-2GHz) Global Positioning System (GPS) carriers and also
satellite mobile phones.
S-Band (2-4GHz) Weather radar, surface ship radar, and some
communications satellites.
C-Band (4-8GHz) Primarily used for full-time satellite TV networks or
raw satellite feeds.
X-Band (8-12GHz) Used in military and radar applications
KU-Band (12-18GHz) Direct broadcast satellite services.
KA-Band (26-40GHz) high-resolution, close-range targeting radars on
military aircraft.
Table 3.1 : Satellite frequency bands and its usage
Satellite Orbits
Figure 3.4 : Satellite Orbits
The altitudes at which satellites can orbit the earth are split into three categories, such as low earth orbit
(LEO), medium earth orbit (MEO), and high earth orbit (HEO).Satellites can orbit around the equator or
the poles, though technically they can orbit the earth on any elliptical or circular path. When a satellite's
orbit matches the rotation of the earth, and it's position over the earth remains fixed, it's called
Geostationary or geosynchronous orbit.
Distance Miles KM 1-way Delay
Low Earth Orbit (LEO)
100-500
160 - 1,400
50 ms
Medium Earth Orbit (MEO)
6,000 - 12,000
10 -15,000
100 ms
Geostationary Earth Orbit (GEO)
~22,300
36,000
250 ms
High Earth Orbit (HEO)
Above 22,300
Faster than 36,000
300 ms or more
Table 3.2 : Orbit Classification
Signal to Noise Ratio
Figure 3.5 : Signal to Noise Ratio for Radio Receiver
Although there are many ways of measuring the sensitivity performance of a radio receiver, the S/N ratio
or SNR is one of the most straightforward and it is used in a variety of applications. However it has a
number of limitations, and although it is widely used, other methods including noise figure are often used
as well. Nevertheless the S/N ratio or SNR is an important specification, and is widely used as a measure
of receiver sensitivity. The difference is normally shown as a ratio between the signal and the noise (S/N)
and it is normally expressed in decibels. As the signal input level obviously has an effect on this ratio, the
input signal level must be given. This is usually expressed in microvolts. Typically a certain input level
required to give a 10 dB signal to noise ratio is specified.
The signal to noise ratio is the ratio between the wanted signal and the unwanted background noise.
It is more usual to see a signal to noise ratio expressed in a logarithmic basis using decibels:
If all levels are expressed in decibels, then the formula can be simplified to:
The power levels may be expressed in levels such as dBm (decibels relative to a milliwatt, or to some
other standard by which the levels can be compared.
4.0 PROCEDURE
Figure 4.1: Uplink transmitter, downlink receiver, and transponder set up
1. The experiment started by connected satellite uplink transmitter, satellite transponder and satellite
downlink receiver to AC mains. Then, the devices all switched on.
2. The frequency for uplink transmitter and uplink transponder set to same frequency.
3. The frequency for downlink receiver and downlink transponder set to same frequency.
4. The transmitter and receiver antenna aligned parallel.
5. The uplink transmitter and downlink receiver set in tone mode by using channel select B.
6. Then, the uplink transmitter and downlink receiver connected oscilloscope.
7. The tone signal waveform from oscilloscope observed and amplitude measured.
8. The experiment repeated by changing the uplink transmitter from tone mode to any other mode.
9. The output waveform results compared for the different modes of uplink transmitter.
10. The tone signal calculated by subtract amplitude of noise from received signal.
11. The signal to noise ratio calculated by using formula.
Signal to noise ratio = S / N
Signal to noise ratio (in dB) = 20 log S / N
Uplink Downlink
Transponder
5.0 EXPERIMENT RESULT
Figure 5.1: The input and the output waveform
Calculation :
S = S1 – N
S = 4.6 V – 270mV
S = 4.33 V
Signal to noise ratio = S / N
Signal to noise ratio = 4.33V / 270mV
Signal to noise ratio = 16.0370
Signal to noise ratio (in dB) = 20 log S / N
Signal to noise ratio (in dB) = 20 log 16.0370
Signal to noise ratio (in dB) = 24.10dB
6.0 DISCUSSION
This lab mainly about signal to noise calculation in satellite communication. Signal to noise ratio
is defined as the key parameter for any radio receiver. Just as its name implies, the signal-to-noise
ratio is a direct comparison, or ratio, of the level of the signal to the amount of noise expressed
in decibels. The abbreviation 'S/N Ratio' is commonly used to represent the term signal-to-noise
ratio and the measurement is usually expressed in decibels (or dB).The signal to noise ratio, or
SNR as it is often termed is a measure of the sensitivity performance of a receiver. This is of prime
importance in all applications from simple broadcast receivers to those used in cellular or wireless
communications as well as in fixed or mobile radio communications, two way radio
communications systems, satellite radio and more. There are a number of ways in which the noise
performance, and hence the sensitivity of a radio receiver can be measured. The most obvious
method is to compare the signal and noise levels for a known signal level like the signal to noise
(S/N) ratio or SNR. Obviously the greater the difference between the signal and the unwanted
noise, for example the greater the S/N ratio or SNR, the better the radio receiver sensitivity
performance. As with any sensitivity measurement, the performance of the overall radio receiver
is determined by the performance of the front end RF amplifier stage. Any noise introduced by
the first RF amplifier will be added to the signal and amplified by subsequent amplifiers in the
receiver. As the noise introduced by the first RF amplifier will be amplified the most, this RF
amplifier becomes the most critical in terms of radio receiver sensitivity performance. Thus the
first amplifier of any radio receiver should be a low noise amplifier. Although there are many ways
of measuring the sensitivity performance of a radio receiver, the S/N ratio or SNR is one of the
most straightforward and it is used in a variety of applications. However it has a number of
limitations, and although it is widely used, other methods including noise figure are often used as
well. Nevertheless the S/N ratio or SNR is an important specification, and is widely used as a
measure of receiver sensitivity. The signal-to-noise ratio (SNR) important because it compares the
level of the signal to the level of noise. Sources of noise can include microwave ovens, cordless
phones, Bluetooth devices, wireless video cameras, wireless game controllers, fluorescent lights,
and more. A ratio of 10-15dB is the accepted minimum to establish an unreliable connection; 16-
24dB (decibels) is usually considered poor, 25-40dB is good and a ratio of 41dB or higher is
considered excellent.
A number of other factors apart from the basic performance of the set can affect the signal to
noise ratio, SNR specification. The first is the actual bandwidth of the receiver. As the noise
spreads out over all frequencies it is found that the wider the bandwidth of the receiver, the
greater the level of the noise. Accordingly the receiver bandwidth needs to be stated. Additionally
it is found that when using AM the level of modulation has an effect. The greater the level of
modulation, the higher the audio output from the receiver. When measuring the noise
performance the audio output from the receiver is measured and accordingly the modulation
level of the AM has an effect. Usually a modulation level of 30% is chosen for this measurement.
All electronic audio devices create some level of noise in audio signals. However, it is important
to keep the noise in the signal as low as possible in order to produce accurate and clear sound. In
short, the lower the signal-to-noise ratio a component produces, the better the aural quality audio
or music that you will hear. In many cases, you can improve the signal-to-noise ratio specification
measurements of your stereo system with a few minor upgrades. Rather than going out and
buying expensive new components, improve the signal-to-noise ratio spec for your system by
using higher quality connection cables. Generally speaking, using a thicker cable with a better
conductor or connector was result in less noise in signals due to cross talk between electronic