Communication engineering nptel online videos, courses. A carrier wave is modulated changed by adding audio. This is further divided into amplitude and angle modulation. 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. What is amplitude modulation, am electronics notes. If the amplitude of the high frequency carrier wave is varied in accordance with the instantaneous amplitude of the modulating signal, then such a technique is called as amplitude modulation. During my simulation, i also show thd fluctuates with increasing frequency modulation index. So, this techniques for combining the e d outputs, envelope detector outputs, we can. Amplitude modulation, usually shortened to am, is a simple way to send a radio signal.
Multiplexingmedium access control 2 digital modulation 3 why modulate. 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. Lecture notes on analogue communication techniques 1. 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. 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. By combining the i and qchannel outputs in phase d. This is the same as the am modulation above but without the carrier. No information is lost, but the energy is redistributed in the frequency domain. So basically if you see instead of using career in pulse modulation like analog or all other analog version like amplitude or frequency modulation, what we are trying to do is. Information signal is usually of low frequency, so it cannot travel far. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave.
Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Sep 15, 20 lecture series on communication engineering by prof. In communications, the analog signal shape, by preagreed convention, stands for a certain number of bits and is called a symbol. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses, youtube iit videos nptel courses.
If you are new to matlab, please go through our tutorials. Sinusoidal modulation slowly increase the modulation signal voltage am over the range 0 v to 4 v i. The amplitude modulation and frequency modulation are graphically shown in. Pdf analog communication system pdf notes ac notes sw. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. A product modulator is used for generating the modulated signal as shown in figure 3. 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. In general it involves translating a baseband signal source. Each part may be of any convenient amplitude at the input to an adder. Amplitude modulation and frequency modulation duration. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. 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. The combined signal is transmitted over a frequency.
Nagaraju associate professor r v college of engineering bangalore. Modulation is the process of encoding information from a message source in a manner suitable for transmission. Amplitude modulation fundamentals i n the modulation process, the baseband voice, video, or digital signal modifies another, higherfrequency signal called the carrier, which is usually a sine wave. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. In this chapter, let us solve a few problems based on the concept of frequency modulation. To understand the angle modulation and demodulation techniques. To understand the complex low pass representations, ssb and vsb modulations. The signal can travel long distances, and appear in faraway places, because of the earths ionosphere. Pdf diffractive optical elements are being used in increasing numbers of applications such as beam. The pulse may take any real voltage value that is proportional to the value of the original waveform. Why modulation is used suitable for signal transmission distanceetc. Pradeep kshetrapal, tutorials point india private limited.
In continuouswave modulation, a high frequency sine wave is used as a carrier wave. Pdf telemetry applications of soqpsk and gmsk based. Amplitude modulation is the simplest of the three to understand. Of all the methods of impressing information onto a carrier signal, am is the oldest. Amplitude modulation or am as it is often called, is a form of modulation used for radio transmissions for broadcasting and two way radio communication applications. Chapter 3 amplitude modulation national sun yatsen university.
The amplitude or the strength of a high frequency carrier wave is changed in accordance with the amplitude of message signal. Digital transmission of analog data 2 digitization process of converting analog data into digital signal example. Qam structure consider the yt in the transimitter yt x1tcos. 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. Communication engineering nptel online videos, courses iit video lectures. Pdf novel full complexamplitude modulation diffractive optical. Onoff modulation change the message signal to a square wave 2 khz and with vpp 4v. Although one of the earliest used forms of modulation it is still used today, mainly for long, medium and short wave broadcasting and for some aeronautical point to point. 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. Am is defined as a process in which the amplitude of the carrier t i i d b t l li l ith b b d ct a cc cos 2. Frequency modulation fm and phase modulation pm have much in common and they are usually concluded as angle modulation, i. Demonstration with professor sandy hill from the university of massachusetts at amherst.
In fact, all radio channels in the am band use this type of modulation. Indian institute of technology kanpur national programme. It is not just at that point the you can combine amplitude and phase in general you do not you can combine amplitude, phase and. Digital communications and signal processing iit kanpur. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio.
The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. Although its old technology, it is still widely used in the following applications. Fm signal or angle modulated signal into an amplitude modulated signal. We can define amplitude modulation by saying that a modulating signal, should produce an am wave of the form well use s instead of v or e to indicate that were talking about a modulated quantity and that it can be either a field or a voltage. To understand the functions of am and fm transmitters and receivers. Combining the dark and light regions of the mask it is possible to create the desired relief in the optical. 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. Design and implementation of amplitude modulator and demodulator introduction communication is the most important needs from the very beginning of civilization.
Surendra prasad, department of electrical engineering,iit delhi. Basic concepts of modulation three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Yet, am continues to be used today in many communication applications. That means, although am increases the amplitude of the modulated signal, it. Enel 471 amplitude linear modulation modulation is a process by which a parameter of a high frequency sinusoid is modified in accordance with the message signal to be transmitted. In addition, it also explains how to use input data from workspace using configuration settings. Principles of communication part i professor aditya k. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. The amplitude modulation am modulation depth figure is complementary to the modulation index. Pulse train pulse amplitude modulation jamadagni h s dcv12004 9 pulse code modulation pcm pam samples analog input low pass filter sample clock jamadagni h s da ad digitally encoded samples. Generation of amplitude modulation basic requirements. Each of these is one bit of information, 0s and 1s. 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.
In this video, i have explained importance of modulation index by following outlines. Questions from video lectures of nptel sl no questions video number time in minutes 1 describe the necessity of modulation in communication. Modulation is a process of translating information signal from low band frequency to high band frequency that is suits the transmission medium. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone line or radio. I want to know what is the actual relation between thd and modulation index frequency and amplitude. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that. 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. Varying these parameters in proportion to the baseband signal results in amplitude modulation am, frequency16 modulation fm, and phase modulation pm, respectively. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. In this video, i have explained amplitude modulation by following outlines. This method is capable of producing nearly 100% modulation with reasonable linearity. This is the simplest form of modulation where the amplitude of the carrier wave is modulated by the analog signal known as. Nptel nptel online certification course course on analog.
Amplitude modulation chapter 3 objectives at the conclusion of this chapter, the reader will be able to. The first of these, the am transmitter, generates such high powers that its prime requirement is efficiency, so quite complex means of. Importance of modulation index in amplitude modulation in. And briefly how do you describe amplitude modulation some. Introduction to amplitude modulation am, modulation index, envelope distortion and over modulation lecture 11 spectrum of amplitude modulated am. This is the most widely used type of am modulation. A signal under study in a communication system is generally expressed as a function of time or as a function of frequency. It also explains conditions required for merge block. Simulink tutorial 12 difference between mux and merge. Amplitude modulation double side band nptel mafiadoc.
When the signal is expressed as a function of time, it gives us an idea of how that instantaneous amplitude of the signal is varying with respect to time. Bikash kumar dey department of electrical engineering iit bombay, powai mumbai 400 076, india subject expert. There are two types of devices in which it may be necessary to the generation of amplitude modulation. A sine wave carrier can be modified by the intelligence signal through amplitude modulation, frequency modulation, or phase modulation. Chapter 3 amplitude modulation national sun yatsen. According to the standard definition, the amplitude of the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal. The use of amplitude modulated analog carriers to transport digital information is a relatively lowquality, lowcost type of digital modulation and, therefore, is seldom used except for very lowspeed telemetry circuits. Calculate the frequency deviation, modulation index, and bandwidth. They can be used to reference the content of each lecture. What is modulation 2 modulation in the modulation process, some characteristic of a highfrequency carrier signal bandpass, is changed according to the instantaneous amplitude of the information baseband signal.
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. Usually the intelligence we are trying to transmit is audio, but of course can be other things such as encoded video or data. The carrier amplitude is constant and the phase variation of the signal contains the information. Types of amplitude modulation am double sideband with carrier we will call it am.
Nptel, lectures on digital communication, lesson 36 7. The transmitter just uses the information signal, v m t to vary the amplitude of the carrier, v co to produce a modulated signal, v am t. Among them, amplitude modulation am is considered the oldest. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. So basically if you see instead of using career in pulse modulation like analog or all other analog version like amplitude or frequency modulation. 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. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Lecture notes signals and systems mit opencourseware. So, this becomes a times real part of or let me combine this i can write lie this n. Amplitude modulation simple english wikipedia, the free.
The three techniques are referred to as amplitude shift keying ask, frequency shift. Introduction ang man shun december 20, 2012 to send multiple signals at one time, one way is to use qam. The original waveform amplitude is quantized with a resulting loss of information. 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. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn. Communication systems a lecture notes by mahesh lohith k. The process of combining a number of separate message signals into a com. Typically the modulation depth is the amplitude modulation index expressed as a percentage.
Introduction to quadrature carrier modulation qcm and demodulation of qcm. This is a carrier symbol that represents one information bit. Time bit baseband amplitude carrier amplitude process of modulation. Simulink tutorial 12 difference between mux and merge block this video explains the difference between mux and merge blocks from simulink library. Telemetry applications of soqpsk and gmsk based modulation for airborne platforms conference paper pdf available december 2012 with 1,832 reads how we measure reads. When drifts away from 0, the qchannel output will have the same polarity as the ichannel output for one direction of phase drift, and opposite polarity for another direction of phase drift. Which means, the amplitude of the carrier signal containing no information varies as per the amplitude of the signal containing information, at each instant. Gate preparation, nptel video lecture dvd, electronicsandcommunicationengineering, communicationtheory, noiseincascadedsystems, amplitude modulation, am wave. A solutions manual is available free to all adopting faculty, which. Now observe that the phase difference between these two carriers is 90. Oct 14, 20 amplitude modulation am is a one of the conventional modulation technique to transmit signals using a carrier wave.
The notes below are primarily still images of the slides and boards seen in the lecture videos. The canonical decompositions of the digital transmitter and the digital receiver convert the block formed by the waveform modu lator, the awgn channel, and the waveform demodulator into an awgn vector channel. Amplitude modulation introduction amplitude modulation is the simplest and earliest form of transmitters am applications include broadcasting in medium and highfrequency applications, cb radio, and aircraft communications basic amplitude modulation the information signal varies the instantaneous amplitude of the carrier am characteristics am is a nonlinear process sum and. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Communication theory noise in cascaded systems exam study. Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc.
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