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

components. Also, keeping the length of connection cables in your stereo at a minimum will also

help reduce the noise created in your audio system.

SNR is a very convenient method of quantifying the sensitivity of a receiver, but there are some

points to note when interpreting and measuring signal to noise ratio. To investigate these it is

necessary to look at the way the measurements of signal to noise ratio, SNR are made. A

calibrated RF signal generator is used as a signal source for the receiver. It must have an accurate

method of setting the output level down to very low signal levels. Then at the output of the

receiver a true RMS AC voltmeter is used to measure the output level. The S/N and (S+N)/N are

used when measuring signal to noise ratio there are two basic elements to the measurement.

One is the noise level and the other is the signal. As a result of the way measurements are made,

often the signal measurement also includes noise as well, i.e. it is a signal plus noise measurement.

This is not normally too much of a problem because the signal level is assumed to be much larger

than the noise. In view of this some receiver manufacturers will specify a slightly different ratio:

namely signal plus noise to noise (S+N/N). In practice the difference is not large, but the S+N/N

ratio is more correct. PD and EMF are occasionally the signal generator level in the specification

will mention that it is either PD or EMF. This is actually very important because there is a factor

of 2:1 between the two levels. For example 1 microvolt EMF and 0.5 microvolt PD are the same.

The EMF (electro-motive force) is the open circuit voltage, whereas the PD (potential difference)

is measured when the generator is loaded. As a result of the way in which the generator level

circuitry works it assumes that a correct (50 Ohm) load has been applied. If the load is not this

value then there will be an error. Despite this most equipment will assume values in PD unless

otherwise stated.

7.0 CONCLUSION

End of this lab, the theory of signal to noise ratio had been learned. Signal-to-noise ratio (abbreviated

SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to

the level of background noise. It is defined as the ratio of signal power to the noise power, often

expressed in decibels. Besides that, the calculation formula to find the signal to noise ratio also

identified. The calculation formula which used to find the value of S/N is signal value divide by noise

value. In case for dB, the 20 log (S/N) formula is used to represent in decibel value. A ratio higher than

1:1 (greater than 0 dB) indicates more signal than noise. While SNR is commonly quoted for electrical

signals, it can be applied to any form of signal such as isotope levels in an ice core or biochemical

signaling between cells.

8.0 REFERENCES

K. N. Raja Rao., 2013. Satellite Communication: Concepts And Applications : Phi Learning Private

Limited, Pg 162-167.

Dharma Raj Cheruku.,2009. Satellite Communication:I.K.International Publishing House Pvt.Ltd, Pg

258-267.

Bruce Elbert,.2008. Introduction to Satellite Communication: Artech House,Inc, Pg 144-150.

Monojit Mitra.,2005. Satellite Communication : Prentice Hall of India Privated Limited, Pg 59-63.

Daniel Minoli.,2015. Innovations in Satellite Communication and Satellite Technology : John Wiley, Pg 55-59.

RUBRIC FOR LAB LONG REPORT ASSESSMENT

Subject : BETT 4803 – SATELLITE COMMUNICATION

Course : 4 BETT

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Theory

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Discussion

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Total Marks =

100

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