This document discusses transmission systems in satellite communications. It begins by defining a transmission line as a device that transmits or guides energy from one point to another. It then discusses how transmission lines carry alternating current and are used to connect radio transmitters and receivers. The document goes on to describe the key components of fiber optic and wireless transmission systems, including transmitters, receivers, optical fiber cables, antennas, and amplifiers. It explains how each component functions and its role in transmitting signals across long distances.

1. Masters of Science in Electronics & Communication Engineering (Evening)
MECE, 6th
Batch, 1st
Semester
Group-B
Communication Engineering
Assignment Name: Transmission System in
Satellite Communication
DEPARTMENT OF APPLIED PHYSICS, ELECTRONICS &
COMMUNICATION ENGINEERING
Islamic University, Kushtiya, Bangladesh
SUBMITTED BY:
Name : MD. ABU OSMAN
Reg No : EV-2418
Roll No : 16150619
Session : Fall-2016
SUBMITTED TO:
PROF. DR. SHAHZAHAN ALI
Dept. of APECE

2. Acknowledgement
The energy may be for lighting, heating, or performing work, or it may be in the
form of signal information (speech, pictures, data, music).
Basically a transmission line has two terminals into which power (or information)
is fed and- two terminals from which power (or information) is received. Thus, a
transmission line may be regarded as a four-terminal device for connecting any and
all electrical devices.
Since the earliest days of telecommunications there has been an ever increasing
need to transmit more data even faster. Initially single line wires were used. These
gave way to coaxial cables that enabled several channels to transmitted over the
same cable. However these systems were limited in bandwidth and optical systems
were investigated.

3. A Transmission line may be defined as a device for transmitting or guiding energy
from one point to another.
It is a specialized cable or other structure designed to carry alternating
current of radio frequency, that is, currents with a frequency high enough that
their wave nature must be taken into account. Transmission lines are used for
purposes such as connecting radio transmitters and receivers with their antennas,
distributing cable television signals, trunklines routing calls between telephone
switching centres, computer network connections and high speed computer data
buses.

4. Wireless System Connection
A wireless system consists of a
radio that works as a transmitter,
receiver, or usually both. A radio
that both transmits and also
receives is also called a transceiver.

5. A coaxial cable carries the signal from the radio to the antenna and vice-versa.
Most commercial communication
antennas have an impedance of 50
ohms, while TV antennas and
cables are usually 75 ohms.
The antenna is the point at which a moving
current in a wire is transformed into an
electromagnetic wave radiating in space.
The wave leaving the wire can be
further guided to travel mostly
one direction.
The guided wave can be further directed
to radiate very strongly in one direction,
as in the case of a waveguide feeding a
parabolic reflector.

6. Fiber optic transmission system
Any fiber optic data transmission system will comprise a number of different
elements. There are three major elements (marked in bold), and a further one
that is vital for practical systems:
 Transmitter (light source)
 Fiber optical cable
 Optical repeater & Amplifier
 Receiver (Detector)
Transmitter
Modern fiber-optic process of communicating using fiber-optics involves the
following basic steps:
 Creating the optical signal involving the use of a
transmitter, usually from an electrical signal
 Relaying the signal along the fiber, ensuring that
the signal does not become too distorted or weak
 Receiving the optical signal
 Converting it into an electrical signal
The information transmitted is typically digital information generated by
computers, telephone systems, and cable television companies.
There are two main types of fiber optic transmitter that are in use today. Both of
them are based around
semiconductor technology:
Light emitting diodes (LEDs)
Laser diodes
An optical fiber junction box. The yellow
cables are single mode fibers

7. Optical Fiber Cable
A fiber optic cable consists of a glass or silica core. The core of the optical fiber is
surrounded by a similar material, i.e. glass or silica, called the cladding that has a
refractive index that is slightly lower than that of the core.
Optical fibers can also be split into
single mode fiber, and
multimode fiber.
The standard for most optical fibers is
125 microns (um) for the cladding and
245 microns (um) for the outer
protective coating.
Multimode optical fibers have core sizes of either 50 or 62.5 microns whereas the
standard for single mode fibers is approximately 8 to 10 microns.
Optical repeater & Amplifier
These repeaters convert the signal into an electrical signal, and then use a
transmitter to send the signal again at a higher intensity than was received, thus
counteracting the loss incurred in the previous segment. Because of the high
complexity with modern wavelength-division multiplexed signals (including the
fact that they had to be installed about once every 20 km), the cost of these
repeaters is very high.
Receiver
Once data has been transmitted across a fiber optical cable, it is necessary for it
to be received and converted into electrical signals
so that it can be processed and distributed to its final
destination.
The main component of an optical receiver is a photo
detector, which converts light into electricity using

8. the photoelectric effect. The primary photo detectors for telecommunications are
made from arsenide. The photo detector is typically a semiconductor-
based photodiode.
A fiber transmission system is often characterized by its bandwidth–distance
product, usually expressed in units of MHz-km. This value is a product of
bandwidth and distance because there is a trade off between the bandwidth of
the signal and the distance it can be carried.
Distributed transmission system is a form of single-frequency network in which a
single broadcast signal is fed via microwave, landline, or communications
satellite to multiple synchronized terrestrial radio transmitter sites. The signal is
then simultaneously broadcast on the same frequency in different overlapping
portions of the same coverage area, effectively combining many small
transmitters to generate a broadcast area rivaling that of one large transmitter or
to fill gaps in coverage due to terrain or localized obstacles.

9. Antenna
Antennas are very important for the overall wireless system performance, and there
are many different types.
An antenna is the structure associated with the region of transition from a guided
wave to a free space wave, radiating RF energy.
Antenna features:
 frequency range (bandwidth)
 Radiation pattern (beamwidth, sidelobes,
backlobe, front-to-back ratio, location of
nulls)
 Maximum gain
 Input impedance
 Physical size and wind resistance
 Cost
The directivity of an antenna is simply the ratio of the maximum power density to
the average power density.
D[dBi] = 10log10 (Pmax / Pav)
The gain is closely related to directivity: in this case you have to take into account
the efficiency η of the antenna:
G[dBi] = 10log10 η(Pmax / Pav)
Typical efficiency is between 0.5 and 0.9, depending on the quality of the
construction and the conductivity of the metal used.
Use high gain antennas to reach long distances, and omni or sectorial antennas to
cover wide areas.
Figure: Wind Load

10. Conclusion:
We come to a conclusion that the day is not so far when there will not be a wire &
stop power theft. Even some electronic gadgets will not need batteries at all. And
also with solar power satellite the need of the electricity will be fulfilled.
Dr. Neville of NASA states, “You don’t need cables, pipes, or copper wires to
receive power.
We can send it to you like a cell phone call – where you want it, when you
want it, in real time”. We can expect with certitude that in next few years‟ wonders
will be wrought by its applications if all the conditions are favorable.