# Communication Systems   Share

## What is Communication Systems

Communication is the act of transmission of information. Every living creature in the world experiences the need to impart or receive information almost continuously with others in the surrounding world. For communication to be successful, it is essential that the sender and receiver understand a common language. This chapter introduces the concepts of communication, namely the mode of communication, the need for modulation, production, and deduction of amplitude modulation. We live in a world of information. Information needed to be communicated from one entity to another. This process of sending and receiving messages from one place to another place in a successful manner is called communication. Note the word successful in the above definition, it implies many things like common understanding by the sender and the receiver during transmission of the information and quality in communication, which implies there is no addition, modification or deletion of the actual information. The growing needs of human beings in the field of communication imposed demands on the complexity of information and speed of transmission.

There are several types of communications which are used in different fields. The main purpose of a communication system is to message signals or transmit information. As, message signals are also known as baseband signals, which designate the band of frequencies and it represents the original signal, as delivered from the source of information. Also, generally no signal is a single frequency sinusoid, but there is a range of frequencies called the signal bandwidth.

## Notes for Communication Systems

Now we will discuss each of the important topics along with an overview of the chapter followed by important formulas of the chapter which will help you in solving numerically related to Magnetic Effects of Current and Magnetism.

## Topics of Communication systems

• Communication system and its elements

• Types of communication system

• Analog and digital signals

• Modulation

• Amplitude modulation

• Frequency modulation

• Pulse modulation

• Pulse code modulation

• Demodulation

• Ground wave propagation

• SKY wave propagation

• Space wave propagation

• Satellite Communication

• Optical fiber

## Overview of Communication Systems

In this chapter, we will study that every communication system has three essential elements irrespective of its nature- transmitter, medium/channel, and receiver. Actually, the transmitter and the receiver may be located geographically at different places. The Channel connects the transmitter and the receiver. The block diagram shown depicts the general form of a communication system.

In a communication system, the transmitter is located at one place, the receiver is located at some other place (maybe far or near) separate from the transmitter and the channel is that physical medium that connects them. Depending upon the type of communication system, a channel may be in the form of wires or cables connecting the transmitter and the receiver or it may be wireless.

Information Source – It is defined as the source produces a signal of the information which needs to be communicated.

Signal – It is defined as the information in an electrical form suitable for transmission is called signal.

Transmitter – It is the device which converts the source signal into a suitable form for transmission through the channel.

Channel – It is defined as the channel connecting the transmitter and the receiver is a physical medium. The channel can be in the form of wires, cables or wireless.

Noise – Whenever the transmitted signal propagates along the channel, it may get distorted due to channel imperfections.

Receiver – It is the equipment in which due to noise and other factors, the corrupted version of the signal arrives at the receiver. The receiver is that device which is used to reconstruct the signal into a recognizable form of the original message for delivering it to the user. The signal at the receiver forms the output.

After this, we will get familiar with basic terminologies used in communication system like attenuation, transducer, amplification, repeater, bandwidth.

In a communication system, the message signal can be music, voice, picture or computer data. Each type of signals mentioned above has different ranges of frequencies. The type of communication system which is needed for a given signal depends on the band of frequencies, is considered essential for the communication process. In a similar way the message signals, different types of transmission media offer different bandwidths. The commonly used transmission media are wire, free space, and fiber optic cable.

## Formulas of Communication Systems

• Modulation Index if maximum and minimum amplitude is given

$m_{a}= \frac{E_{max}-E_{min}}{E_{max}+E_{min}}$

• Total Modulation Index

$m_{t}= \sqrt{m_{1}^{2}+m_{2}^{2}}+...$

• Voltage equation for AM wave

$e_{c}= E_{c}\cos \omega _{c}t$

$e_{m}= E_{m}\sin \omega _{m}t$

$e= \left ( E_{c} +e_{m}\sin \omega _{m}t\right )\cdot \sin \omega _{e}t$

•  Modulated Wave

$e= E_{e}\sin \omega _{c}t+\frac{m_{0}E_{c}}{2}\cdot \cos \left ( \omega _{c}-\omega _{m} \right )t-\frac{m_{0}E_{e}\cdot}{2} \cos \left ( \omega _{c}+\omega _{m} \right )t$

• Power in AM waves

$P=\frac{ V^{2}_{rms}}{R}$

• Carrier Power

$P_{c}= \frac{\left ( \frac{E_{c}}{\sqrt{2}} \right )^{2}}{R}= \frac{E^{2}_{c}}{2R}$

• Total Power of sidebands

$P_{sb}= \frac{\left ( \frac{m_{a}E_{c}}{2\sqrt{2}} \right )^{2}}{R}+ \frac{\left ( \frac{m_{a}E_{c}}{2\sqrt{2}} \right )^{2}}{R}= \frac{m{_{a}}^{2}E{_{c}}^{2}}{4R}$

• Total power of AM wave

$P_{total }= P_{c}+P_{sb}$

$=\frac{E{_{c}}^{2}}{2R} \left ( 1+\frac{m{_{a}}^{2}}{2} \right )$

• The modulation index of frequency modulation

$m_{f}= \frac{\delta _{max}}{f_{m}}$

$= \pm \frac{KE_{m}}{f_{m}}$

• The effective refractive index of the ionosphere

$n_{eff}= n_{0}\left [ 1-\frac{N{_{e}}^{2}}{\epsilon _{0}m\omega ^{2}} \right ]^{1/2}$

$n_{eff}= n_{0}\left [ 1-\frac{80.5N}{f^{2}} \right ]^{1/2}$

## How to prepare a Communication System

First, you should have good command over the concepts of the Communication systems and you should also know how to apply them well at the time of the entrance exam or while solving questions. Please try to understand each concept from this chapter, with the help of theory, questions with solutions and video lectures on each important concept. For each concept practice enough problems so that you have a thorough understanding of the concept. Solve all the questions at home with proper concentration and try to do all calculation by yourself without seeing the solution first.

## How to Solve Communication Systems Questions.

1. Have crystal clear concepts of Transmitter, transmission channel, and receiver

2. Remember all the formulas and its condition like the range of the antenna, amplitude modulated signal frequency, etc.

3. Draw all the flow diagram of each part of the communication system.

This particular chapter does not have too many concepts and the problem coming in the examination does not have too many varieties. The main thing is that the basic formula and the flow diagram should be remembered. The function of all the equipment should be clear.

## Communication Systems Tips

1. This chapter is more of a concept based chapter there are many points to memorize, hence practice is the key here for getting a good hold on this chapter.

2. Lots of question will ask on the range of the antenna, modulation of wave and the functions of the equipment used.

3. Make a plan to prepare for this chapter and Stick to a Timetable.

4. Study the concept first and then start solving Communication systems questions. Don't go through question directly without knowing the concept.

5. Solve previous year question of various exam from this chapter.

6. Revise concepts on regular intervals.

Because as said by Vince Lombardi

"Practice does not make perfect. Only perfect practice makes perfect."

## Communication Systems Books

For Communication systems, chapter concepts in NCERT are enough but you will have to practice lots of questions including previous year questions and you can follow other standard books available for competitive exam preparation like Concepts of Physics (H. C. Verma) and Understanding Physics by D. C. Pandey (Arihant Publications).

## Physics Chapter wise Notes For Engineering and Medical Exams

 Chapters No. Chapters Name Chapter 1 Physics and Measurement Chapter 2 Kinematics Chapter 3 Laws of motion Chapter 4 Work Energy and Power Chapter 5 Rotational Motion Chapter 6 Gravitation Chapter 7 Properties of Solids and Liquids Chapter 8 Kinetic theory of Gases Chapter 9 Thermodynamics Chapter 10 Oscillations and Waves Chapter 11 Electrostatics Chapter 12 Current Electricity Chapter 13 Magnetic Effects of Current and Magnetism Chapter 14 Electromagnetic Induction and Alternating currents Chapter 15 Electromagnetic Waves Chapter 16 Optics Chapter 17 Dual Nature of Matter and Radiation Chapter 18 Atoms And Nuclei Chapter 19 Electronic devices Chapter 21 Experimental skills

### Topics from Communication Systems

• Basic elements of a Communication System ( JEE Main, KCET, TS EAMCET, MET, MHT-CET, AP EAMCET, AP EAMCET Pharmacy, TS EAMCET Pharmacy, GUJCET Pharmacy, KVPY SA, KVPY SB/SX ) (107 concepts)
• Bandwidth of signals, bandwidth of transmission medium ( JEE Main, KCET, TS EAMCET, MET, MHT-CET, AP EAMCET, AP EAMCET Pharmacy, TS EAMCET Pharmacy, GUJCET Pharmacy, KVPY SA, KVPY SB/SX ) (11 concepts)
• Need for modulation, Amplitude and Frequency modulation ( JEE Main, KCET, TS EAMCET, MET, MHT-CET, AP EAMCET, AP EAMCET Pharmacy, TS EAMCET Pharmacy, GUJCET Pharmacy, KVPY SA, KVPY SB/SX ) (90 concepts)
• Sky and space wave propagation ( JEE Main, KCET, TS EAMCET, MET, MHT-CET, AP EAMCET, AP EAMCET Pharmacy, TS EAMCET Pharmacy, GUJCET Pharmacy, KVPY SA, KVPY SB/SX ) (60 concepts)
• Propagation of electromagnetic waves in the atmosphere ( JEE Main, KCET, TS EAMCET, MET, MHT-CET, AP EAMCET, AP EAMCET Pharmacy, TS EAMCET Pharmacy, GUJCET Pharmacy, KVPY SA, KVPY SB/SX ) (55 concepts)
• Communication Systems ( JEE Main, KCET, TS EAMCET, MET, MHT-CET, AP EAMCET, AP EAMCET Pharmacy, TS EAMCET Pharmacy, GUJCET Pharmacy, KVPY SA, KVPY SB/SX ) (32 concepts)

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