ECE,7 th Sem
• What is satellite?.
• Types of Satellite & its advantages over
• Why do satellites stay moving and in orbit?.
• Components of Satellite.
• TTC & M.
• Look Angle Determination.
• Types of Antenna.
• Link Design for Satellite Communication.
• Satellite Orbit.
• Applications of Satellite Communication.
• Effects of Earth and Third body effects on
• Satellite Communication – “Future”.
What is a Satellite?
• The word satellite originated from the Latin
word “Satellit”- meaning an attendant, one
who is constantly hovering around & attending
to a “master” or big man.
• For our own purposes however a satellite is
simply any body that moves around another
(usually much larger) one in a mathematically
predictable path called an orbit.
• From a Communication stand point, a satellite
may be considered as a distant microwave
repeater that receives uplink transmission and
provides filtering , amplification, processing and
frequency translation to the downlink band for
Types of Satellite
• Anti-Satellite weapons (Killer satellites)
• Astronomical satellites
• Communications satellites
• Miniaturized satellites
• Navigational satellites(mobile
communication for location)
• Reconnaissance satellites( for military or
• Earth observation satellites (environmental
• Solar power satellites
• Weather satellites
Satellite vs Terrestial
Advantages of satellites:
The coverage area of a satellite greatly exceeds that of
a terrestrial system.
Transmission cost of a satellite is independent of the
distance from the center of the coverage area.
Satellite to Satellite communication is very precise.
Higher Bandwidths are available for use.
Disadvantages of satellites:
Launching satellites into orbit is costly.
Satellite bandwidth is gradually becoming used up.
There is a larger propagation delay in satellite
communication than in terrestrial communication.
How do we escape gravity & place
an object in orbit?
• If an object is
fired fast enough
it should escape
the earths pull.
• This is done
through the use
• Stage 1: Raises the
payload e.g. a satellite to
an elevation of about 50
• Stage 2: Satellite 100
miles and the third stage
places it into the transfer
• Stage 3: The satellite is
placed in its final geo-
synchronous orbital slot
by the AKM, a type of
rocket used to move the
TTC &M antenna
For altitude and Controller
Look Angle Determination
The elevation of a satellite,η is the angle which a satellite makes with the
tangent at the specified point on the earth.
η = arc tan [(cosψ-σ)/ sin ψ]
Where, coverage angle ψ = arc cos (cosθc cosφcs )
φcs = φc - φs and σ =R /(R+h) = 0.151
In terms of elevation angle:
ψ = 900 – η-sin-1(cos η / 6.63235)
In terms of tilt angle : ψ = sin -1(6.6235 sinγ- γ)
where θc = latitude of earth station, φc = the longitude, φs = longitude of
sub satellite point, R=radius of earth, h=satellite height above equator
Tilt angle γ = arc tan [sin ψ / (6.6235-cos ψ)
The azimuth ξ is the angle which the satellite direction
makes with the direction of true north measured in the
The azimuth ξ = arc tan [tan φcs /sinθc]
in northern hemisphere:
ξ =1800 + A0;when the satellite is to the west of earth station.
ξ =1800 - A0;when the satellite is to the east of earth station
in southern hemisphere.
ξ =3600 - A0;when the satellite is to the west of earth station.
ξ =A0;when the satellite is to the east of earth station.
Tx Source Output Rx
• Based on RF transmissions.
• Satellite communication systems consist of
ground-based or earth stations (i.e.parabolic
antennas) and orbiting transponders.
• The transponder receives HF microwaveSsignal from
AM a VHF UHF L C X KuKa V Q
the ground unit (the uplink) amplifies it and then100
0.1 1 10 100 1 10
transmits it back to earth (the downlink).
• For a communication satellite to function properly,
it must remain stationary with respect to its
position over the earth i.e it mustBands within line of
sight of its earth stations at all times.To remain
stationary, the satellite mustSpace Bands
traverse its orbit at
the same rate as the earth rotates.and Space)
IN P U T R F
500 MH z
M IX E R
HP A DA
500 MH z O U TP U T
Earth Station Architecture
Elevation Angle Local Horizon
Diplexer Tracking & Control
RF IF Baseband
HPA Modulator Signals I/P
RF IF Baseband
LNA Demodulator Signals O/P
Television Uplink Service
FM Up Baseband
Mod Converter processor
Television Downlink Service
Baseband FM Down
processor Demod Converter
* Circular orbits are simplest
* Inclined orbits are useful for
coverage of equatorial regions.
* Elliptical orbits can be used to
give quasi stationary behavior
viewed from earth using 3 or 4
* Orbit changes can be used to
extend the life of satellites.
Satellite orbits are also classified
based on their heights above the
GEO(Geostationary Earth Orbit )
LEO(Low Earth Orbit )
MEO (Medium Earth Orbit )
HAPs (High Altitude Platform )
LEO: Low Earth Obit
MEO: Medium Earth Orbit
LEO: 500 - 900 km GEO: Geostationary Earth Orbit
MEO: 5,000 - 12,000 km
GEO: 36,000 km
GEO:-These satellites are in orbit 35,786 km above the
earth’s surface along the equator.Objects in Geostationary
orbit revolve around the earth at the same speed as the
earth rotates. This means GEO satellites remain in the same
position relative to the surface of earth.
LEO:-LEO satellites are much closer to the earth than GEO
satellites, ranging from 500 to 1,500 km above the surface.
LEO satellites don’t stay in fixed position relative to the
surface, and are only visible for 15 to 20 minutes each pass.
A network of LEO satellites is necessary for LEO satellites to
MEO:-A MEO satellite is in orbit somewhere between
8,000 km and 18,000 km above the earth’s surface. MEO
satellites are similar to LEO satellites in functionality.MEO
satellites are visible for much longer periods of time thanLEO
satellites, usually between 2 to 8 hours.MEO satellites have
a larger coverage area than LEO satellites.
MOLNIYA:-Used by Russia for decades.
Molniya Orbit is an elliptical orbit. The
satellite remains in a nearly fixed position
relative to earth for eight hours.A series of
three Molniya satellites can act like a GEO
satellite.Useful near polar regions.
HAP:-One of the newest ideas in satellite
communication.A blimp or plane around
20 km above the earth’s surface is used as a
satellite.HAPs would have very small
coverage area, but would have a
comparatively strong signal.Cheaper to put in
position, but would require a lot of them in a
Satellite Communications - Future
• Government and private satellite systems
for telecom and broadcast services
• Capacity enhancement in tune with
• Diversity of services through new
• Direct to Home (DTH) Broadcast
System(with moe clarity)
• Mobile communications service
• Digital Audio Broadcast System
• Wide Area, Wide band Multimedia
• Satellite assisted navigation and
• Emergency Alert Services & Disaster
• Health Communications Support Services
• Backbone for National Information
* ONE OF THE LARGEST DOMESTIC SATCOM
SYSTEMS - Ku, C, S BANDS
* MULTI-PURPOSE :TELECOM, TV,METEOROLOGY
* 82 TRANSPONDERS, GLOBAL/DOMESTIC
BEAMS * LEASE OF CAPACITY TO INTELSAT
INSAT-1 INSAT-3B INSAT-3E
SLV-3 ASLV PSLV GSLV
WEIGHT(T) 17 40 294 400
PAYLOAD 40 kg IN LEO 150 kg IN LEO 1200 kg SSO 2000 kg GTO
LAUNCHES 4 (79-83) 4 ( 87-94) 5 (93-to-date ) (Year 2000)