At this point we know that modulation refers to intentionally modifying a sinusoid such that it can carry lowerfrequency information from a transmitter to a receiver. Modulationtypesamplitude,frequency,phase modulation. Amplitude modulation and frequency modulation lecture docsity. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. Intro to generation of ask amplitude shift keying ask in the context of digital communications is a modulation process, which imparts to a sinusoid two or more discrete amplitude levels. The amount by which the amplitude of the carrier wave increases and decreases depends on the amplitude of the information signal and is known as modulation index or depth of modulation. A percent modulation of greater than 100% is usually to be avoided. Today we are going to study amplitude modulation, what are its uses and limitations. Amplitude modulation let a in the above mentioned signal be. In this chapter, let us solve a few problems based on the concept of frequency modulation. The demonstration centers around a number of signals displayed in both the time domain and the frequency domain using a signal generator, an oscilloscope to view the signal.
The fact that rapidly modulating the amplitude of one wave results in a waveform identical to playing two notes of different frequencies is quite remarkable and for more information on such wave interference, please see our wave interference and beat frequency demo. The concluding part will be spent looking at the more popular form of high level modulation known as collector modulation or heising, named after its inventor. There are two types of devices in which it may be necessary to the generation of amplitude modulation. In amplitude modulation, it is the voltage level of the signal to be transmitted that changes the amplitude of the carrier in proportion, see figure 63. View and download powerpoint presentations on amplitude modulation and demodulation ppt. Nptel nptel online certification course course on analog. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%.
Lecture 1 introduction to communication engineering. The first of these, the am transmitter, generates such high powers that its prime requirement is efficiency, so quite complex means of. Phase modulation is mathematically related to frequency modulation as. In chapter 3 we studied the theory of amplitude modulation, but we never actually built an am transmitter. Chapter amplitude modulation and demodulation, ppt, adc. Communication engineering nptel online videos, courses iit video lectures.
Amplitude modulation am 9 t15 use speech or music from trunks as the message, and show that this also generates a trapezoid, and that setting the message amplitude so that the depth of modulation reaches unity on peaks a triangle is especially easy. Amplitude modulation is a very basic form of modulation, and although its simplicity is one of its major advantages, other more sophisticated systems provide a number of advantages. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. The message signal is, for example, a function of the sound to be reproduced by a. Because of amplitude modulation wavelength, am signals can propagate longer distances. Nptel video lectures, iit video lectures online, nptel youtube lectures. Farshad lahouti january 20, 2003 winter 2003 uw, ece 318 lecture notes 2 information source signal modulator propagation channel signal demodulator information destination analog communication system analog signals may be transmitted directly via carrier modulat ion over. Communication engineering communication engineering. Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. A sinusoidal modulating waveform of amplitude 5 v and a frequency of 2 khz is applied to fm generator, which has a frequency sensitivity of 40 hzvolt. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses, youtube iit videos nptel courses. Accordingly it is worth looking at some of the disadvantages of amplitude modulation. Questions from video lectures of nptel sl no questions video number time in minutes 1 give some examples for the communication systems which use space as the channel. In general, video modulation means that a higher frequency carrier wave is modified according to the original video signal.
Video modulation is a strategy of transmitting video signal in the field of radio modulation and television technology. Operation of varying amplitude, frequency or phase of carrier signal accordingly with the instantaneous amplitude of the message signal is called modulation modulation adding information to a carrier signal. Amplitude modulation a1 49 you will see in this experiment, and in others to follow, that there is no problem in generating an am signal with a depth of modulation exceeding 100%, and without. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Communication engineering nptel online videos, courses. Effectively it is formed by having two carriers 90 out of phase. Sep 15, 20 lecture series on communication engineering by prof.
When the modulating information signal a sine wave is applied, the carrier amplitude. Lecture series on communication engineering by prof. Amplitude modulation am, demodulation and their circuit. Principles of communication systems 20022003 8 chapter 7. In this lecture we will study amplitude modulation and a device which can be used as an amplitude modulator. Click on the dates for streamed videos from youtube. Surendra prasad, department of electrical engineering,iit delhi. This document is highly rated by computer science engineering cse students and has been viewed 2846 times. Marvels of modern technology in this age are increasing by the day. In modulation, one characteristic of a signal generally a sinusoidal wave known as the carrier is changed based on the information signal that we wish to transmit modulating signal.
Lecture 10 introduction to amplitude modulation am, modulation index, envelope distortion and over modulation. Nagaraju associate professor r v college of engineering bangalore. Types of modulation 6 flynnkatz 7810 analog modulation amplitude modulation, am frequency modulation, fm double and single sideband, dsb and ssb digital modulation phase shift keying. Transmitters that transmit amplitude modulated signals require an am modulator circuit to produce the required signal. Among them, amplitude modulation am is considered the oldest. So basically if you see instead of using career in pulse modulation like analog or all other analog version like amplitude or frequency modulation. Demonstration with professor sandy hill from the university of massachusetts at amherst. Amplitude modulation can be used to match audio frequencies to radio frequencies. Introduction to amplitude modulation am, modulation. Amplitude modulation and demodulation ppt xpowerpoint.
Radio broadcasting, am radio, television, color television, high. Its still used in radio systems to transmit audio signals although it has lesser in popularity compared to fm due to its lower signal to noise ratio. Introduction what is communication transmitter channel receiver a communication system process of conveying message or information transmitter modifies the message signal into a form which is suitable for transmission over channel which is achieved by modulation information source. Calculate the frequency deviation, modulation index, and bandwidth.
Modulation 5 linguistic aspects of mishearing 6 a good tempo of speech in english nptel. Amplitude modulation am 9 t15 use speech or music from trunks as the message, and show that this also generates a trapezoid, and that setting the message amplitude so that the depth of modulation reaches unity on peaks a triangle is especially easy to do, using the gain control g of the adder. This strategy enables the video signal to be transmitted more efficiently through long distances. Pdf telemetry applications of soqpsk and gmsk based.
There are many ways in which amplitude modulation can be generated and a variety of circuits that can be used. Lecture 7 analog modulation of carriers lecture 8 amplitude modulation lecture 9 amplitude modulation lecture 10 single sideband modulation lecture 11 suppressed sideband modulation lecture 12 vsb modulation superhet receiver lecture superhet receiver etc lecture 14 practical mixerseffects of tonal lecture 15 angle. Lecture notes on analogue communication techniques 1. The extent of amplitude variation in am about a unmodulated carrier amplitude is measured in terms of a factor called modulation index. So basically what we do, we modulate the amplitude of the pulses according to the input. In general, amplitude modulation definition is given as a type of modulation where the amplitude of the carrier wave is varied in some proportion with respect to the modulating data or the signal. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm.
This deteriorates the quality of the original signal at the receiving end and causes problems in the quality of the signal. Although amplitude modulation is not as widely used as it was many years ago, it is still used. Am is widely used for the transmission of data in everything from short range wireless links such as wifi to cellular telecommunications and much more. Charts, graphs, drawings, maps, diagrams, tables, etc research and. Amplitude modulation, spectrum of am signal, the balanced modulator, the square law. A product modulator is used for generating the modulated signal as shown in figure 3. Jagannatham of iit kanpur explains the following concepts in principles of communication systemsi 1. What we do in am, very roughly,is to throw away the frequency content of. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio. For amplitude modulation, we use simple and low cost circuit.
Amplitude modulation definition, types, solved examples. Gate preparation, nptel video lecture dvd, electronicsandcommunicationengineering, linearintegratedcircuits, amplitude modulation, current mirror, current. One is pulse amplitude modulation, so in pulse amplitude modulation what we do, suppose we have a message signal okay. Telemetry applications of soqpsk and gmsk based modulation for airborne platforms. Digital modulation in digital communications, the modulation process corresponds to switching or keying the amplitude, frequency, or phase of a sinusoidal carrier wave according to incoming digital data three basic digital modulation techniques amplitude shift keying ask special case of am. Apr 08, 2020 chapter amplitude modulation and demodulation, ppt, adc, semester, engineering computer science engineering cse notes edurev is made by best teachers of computer science engineering cse. Am demodulators are used within any piece of radio equipment that is used for am broadcast reception or radio communications systems that use amplitude modulation. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Amplitude modulation systems are susceptible to noise generation. A complete transmitter consists of many different stages and hundreds of electronic components. It is well understood that the pulse amplitude modulation pam representation of continuous phase modulation. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam to design the simulink model of the dsbam to analyze each signal in time and frequency domains using time scope and spectrum analyzer.
Bikash kumar dey department of electrical engineering iit bombay, powai mumbai 400 076, india subject expert. Introduction to communication engineering vtunptelnmeict. What is amplitude modulation, am electronics notes. Practical mixers effects of tonal video lecture, online training. The method of varying amplitude of a highfrequency carrier wave in accordance with the information to be transmitted, keeping the frequency and phase of the carrier wave unchanged is called amplitude modulation. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam.
Nptel provides elearning through online web and video courses various. Generation of amplitude modulation basic requirements. Vestigial sideband modulation, frequencydomain description, generation of vsb modulated wave, timedomain description, envelop detection of vsb wave plus carrier, comparison of amplitude modulation techniques, frequency translation, frequency division multiplexing, application. Find powerpoint presentations and slides using the power of, find free presentations research about amplitude modulation and demodulation ppt.
There are many ways to embed a message in a carrier. To generate and demodulate an amplitude shift keyed ask signal and a binary fsk signal. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Amplitude modulation an overview sciencedirect topics. In early am transmitters the amplitude modulator circuit was a key element of the transmitter. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. It is used for video transmission in all the worlds various tv systems to conserve bandwidth.
Digital communication systems ee419 recorded lectures. We wish to use the carrier wave to carry the message signal, so that the message signal can appropriately be transmitted over a bandpass channel. Amplitude modulation am, variation of the amplitude of a carrier wave commonly a radio wave in accordance with the characteristics of a signal, such as a vocal or musical sound composed of audiofrequency waves. Amplitude modulation double side band nptel mafiadoc. But phase modulation seems to be in a different categorypm radio is by no means a common term. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. Video lesson practical mixers effects of tonal video lecture, online training.
Pdf analog communication system pdf notes ac notes sw. Spectra have a typical trapezoidal shape in linear frequency and amplitude in decibels. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. These form some of the main uses of amplitude modulation. To construct a working transmitter or receiver, a knowledge of rf circuit principles is necessary. Amplitude modulation or am is a method to transmit signals via electromagnetic transmission. So depending on and suppose this is the pulse strength which goes like this okay, it will have uniform period of either t or ts let us say. As illustrated in figure 5, the amplifier is biased class c and the output rf signal amplitude is modulated by causing the collector supply voltage to vary with the modulation voltage. Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. Nptel syllabus better spoken english video course course outline. The information is considered as the modulating signal and it is superimposed on the carrier wave by applying both of them to the. Modulation is the process of converting low frequency signals into high frequency signals, so that they can be radiated and recovered at a remote location.
With no modulation, the am carrier is transmitted by itself. Learn about two circuits that can extract the original information from an amplitude modulated carrier signal. There are no amplitude scales shown, but you should be able to deduce the depth. Aug 03, 2019 angle modulation nptel pdf understanding frequency modulation fm, frequency shift keying fsk, sundes any modulation method that changes the angle instead of the amplitude is. Lecture 10 introduction to amplitude modulation am, modulation index.
A typical audio frequency of 3000 hz has a wavelength of 100 km and. Usually the intelligence we are trying to transmit is audio, but of course can be other things such as encoded video or data. Timedomain description, frequencydomain description, generation of am wave. If not smartphones, you at least have a device at your place you can pick up and call a person who may be situated in any part of the world. This limits the applications of amplitude modulation to radios, vhf, and systems used for one to one communications only. Linear integrated circuits amplitude modulation exam study. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Phase modulation is similar to frequency modulation and is an important technique in digital communication systems. Demonstration of amplitude modulation video lectures. Nptel video lectures, iit video lectures online, nptel youtube. Commutator determines the synchronization and sequence of the channels signals to be sampled. Modulation presented by nidhi baranwal mca 6th sem 2.
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