Chapter 25: Satellite Communications – Review Notes

(Last Updated On: December 8, 2017)

Chapter 25: Satellite Communications

This is the summary notes of the important terms and concepts in Chapter 25 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.


CHAPTER 25

SATELLITE COMMUNICATIONS


Items

Definitions

Terms

1

A celestial body that orbits around a planet.

Satellite

2

Man-made satellites that orbit earth, providing a multitude of
communication functions to a wide variety of consumers, including military,
governmental, private and commercial subscriber.’

Communications
Satellites

3

A satellite radio repeater which
Consists of :
·        
input
Bandlimiting device (BPF)
·        
input
low-noise amplifier (LNA)
·        
frequency
translator
·        
low
level amplifier
·        
output
bandpass filter

Transponder

4

It consists of one or more satellite space vehicles, a
ground-based station to control the operation of the system, and a user
network of earth stations that provides the interface facilities for the
transmission and reception of terrestrial communications traffic through the
satellite system.

Satellite System

5

It includes control mechanism that supports the payload
operation.

Bus

6

The actual user information conveyed through the system.

Payload

7

A type of satellite wherein it simply “bounces” signals from
one place to another.

Passive Reflector

8

A natural satellite of Earth, visible by reflection of
sunlight having a slightly elliptical orbit.

Moon

9

Used by passive satellites for tracking and ranging purposes.

Radio Beacon
Transmitters

10

Launched by Russia, the first active earth satellite in 1957.
It transmitted telemetry for 21 days.

Sputnik I

11

A type of satellite capable of receiving, amplifying,
reshaping, regenerating and retransmitting information.

Active Satellite

12

Satellite launched by U.S., it transmitted telemetry
information for nearly five months.

Explorer I

13

Satellite launched by NASA in 1958, a 150-pound conical-shaped
satellite. It was the first artificial satellite used for relaying
terrestrial communications.

Score

14

The first active satellite to simultaneously receive and
transmit radio signals.

Telstar I

15

Launched in 1963, and was used for telephone television,
facsimile and data transmission and accomplished the first successful
transatlantic video transmission.

Telstar II

16

Launched in February 1963, was the first attempt to place a
geosynchronous satellite into orbit.

Syncom I

17

It was the first commercial telecommunications satellite. It
launched from Cape Kennedy in 1965 and used two transponders. Also called as
Early Birds. It stands for International Telecommunications Satellite.

Intelsat I

18

Domestic satellite launched by former Soviet Union in 1966. It
means “lighting”.

Molya

19

A German astronomer who discovered the laws that governs
satellite motion.

Johannes Kepler

20

It may be simply stated as:
The planets move in ellipses with the sun at one focus
The line joining the sun and the planet sweeps out equal
intervals of time.
The square of the time of revolution of a planet divided by
the cube of its mean distance from the sun gives a number that is the same
for all planets.

Kepler’s Law

21

The point in an orbit closest to earth.

Perigee

22

The point in an orbit farthest from the earth.

Apogee

23

It states that the square of the periodic time of orbit is
proportional to the cube of the mean distance between the primary and the
satellite.

Harmonic Law

24

High-altitude earth-orbit satellites operating primarily in
the 2-GHz to 18 GHz frequency spectrum with orbits Satellite 22,300 miles
above earth’s surface.
Advantages of Geosynchronous Satellite:
·        
It
remain almost stationary in respect to a given earth station.
·        
Available
to earth within their shadows 100% of the time.
·        
No
need to switch from one geosynchronous satellite to another as they orbit
overhead
·        
The
effects of Doppler shift are negligible
Disadvantages of geosynchronous Satellite:
·        
It
requires sophisticated and heavy propulsion device onboard to keep them in a
fixed orbit
·        
Much
longer propagation delays
·        
Requires
higher transmit power and more sensitive receivers because of the longer
distances and greater path loss.
·        
High
precision spacemanship is required.

Geosynchronous
Satellite

25

The angle between the earth’s equatorial plane and the orbital
plane of a satellite measured counter clockwise at the point in the orbit
where it crosses the equatorial plane traveling from south to north called
the ascending node.

Angle of Inclination

26

The point where the polar or inclines orbit crosses the
equatorial plane travelling from north to south.

Descending Node

27

The line joining the ascending and descending node.

Line of Nodes

28

It is when the satellite rotates in an orbit directly above
the equator, usually in a circular path.

Equatorial Orbit

29

It is when the satellite rotates in path that takes over the
North and the South poles in an orbit that is close to earth and passes over
and very close to both the North and South Poles.

Polar Orbit

30

The noise power normalized to a 1 Hz bandwidth, or the noise
power present in a 1Hz bandwidth.

Noise Density

31

It identifies the system parameters and is used to determine
the projected carrier-to-noise ratio and energy Bit-to-noise density ratio at
both the satellite and earth station receivers for a given modulation scheme.

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Chapter 25: Satellite Communications – Review Notes
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