The message signal is then used to electrically vary the amplitude. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. A typical audio frequency of 3000 hz has a wavelength of 100 km and. So basically what we do, we modulate the amplitude of the pulses according to the input. Amplitude modulation double side band nptel mafiadoc. In the frequency domain, amplitude modulation corresponds to translating the baseband spectrum to a band surrounding the carrier frequency. Sep 01, 2018 phase modulation is a modulation pattern for conditioning communication signals for transmission.
The message signal is, for example, a function of the sound to be reproduced by 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. Amplitude modulation okay so far we have already discussed about some aspect of signals like fourier series, fourier. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm.
Modulation presented by nidhi baranwal mca 6th sem 2. Transmitters that transmit amplitude modulated signals require an am modulator circuit to produce the required signal. Hence, how the shape of carrier wave is changed is the key to classify the types of video modulation. This is accomplished by heterodyning the intelligence frequency with the carrier frequency. Telemetry applications of soqpsk and gmsk based modulation for airborne platforms. The first of these, the am transmitter, generates such high powers that its prime requirement is efficiency, so quite complex means of. 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. Apr 18, 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.
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. Spectra have a typical trapezoidal shape in linear frequency and amplitude in decibels. The carrier frequency, fc, should be larger than the highest spectral component. 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. Surendra prasad, department of electrical engineering,iit delhi. Usually the intelligence we are trying to transmit is audio, but of course can be other things such as encoded video or data. Amplitude modulation or am is a method to transmit signals via electromagnetic transmission. This strategy enables the video signal to be transmitted more efficiently through long distances. 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. 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. The extent of amplitude variation in am about a unmodulated carrier amplitude is measured in terms of a factor called modulation index. Nptel video lectures, iit video lectures online, nptel youtube. Introduction to communication system, need for modulation, frequency division multiplexing, amplitude modulation, definition, time domain and frequency domain description. In this lecture we will cover continuoustime modulation.
Bikash kumar dey department of electrical engineering iit bombay, powai mumbai 400 076, india subject expert. 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 this chapter, let us solve a few problems based on the concept of frequency modulation. This document is highly rated by computer science engineering cse students and has been viewed 2851 times. One is pulse amplitude modulation, so in pulse amplitude modulation what we do, suppose we have a message signal okay. 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. 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 electrical signal is called the message or baseband signal. Marvels of modern technology in this age are increasing by the day. 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. 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.
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. 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. We will discuss communication applications, such as frequencydivision multiplexing and singleside band modulation. Am demodulation amplitude modulation refers to any method of modulating an electromagnetic carrier frequency by varying its amplitude in accordance with the message intelligence that is to be transmitted. Qam structure consider the yt in the transimitter yt x1tcos. Communication engineering nptel online videos, courses. Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. Gate preparation, nptel video lecture dvd, electronicsandcommunicationengineering, linearintegratedcircuits, amplitude modulation, current mirror, current. The two most common forms of amplitude modulation use either a complex carrier or a single sinusoidal carrier. What is amplitude modulation, am electronics notes.
It is well understood that the pulse amplitude modulation pam representation of continuous phase modulation. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. 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. Lecture series on communication engineering by prof.
Commutator determines the synchronization and sequence of the channels signals to be sampled. Ok, well, so what weve done, so far, for continuous time and discrete time, is to talk about modulation, amplitude modulation with complex exponential and sinusoidal carriers. To generate and demodulate an amplitude shift keyed ask signal and a binary fsk signal. In this video tutorial, we will provide a general introduction of terms of communication systems with emphasis on wireless transmission and reception. Experiment 5 amplitude modulation national instruments. 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. Generation of amplitude modulation basic requirements. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. The first of these, the am transmitter, generates such high powers that its prime requirement is efficiency, so quite complex means of am generation may be used. Nptel nptel online certification course course on analog communication by prof. 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. There are many ways in which amplitude modulation can be generated and a variety of circuits that can be used. Former deputy sheriff eddy craig right to travel traffic stop script washington state law duration.
The modulation index can be used to make the carrier amplitude more or less sensitive to the variations in the value of the baseband signal. 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. Pradeep kshetrapal, tutorials point india private limited. Introduction ang man shun december 20, 2012 to send multiple signals at one time, one way is to use qam. The video signal and carrier wave both exist in waveform and when the carrier wave carries the video signal, the shape of carrier wave is changed and the changed carrier wave is the rf signal. Principles of communication systems 20022003 8 chapter 7. Communication engineering communication engineering. A product modulator is used for generating the modulated signal as shown in figure 3. 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. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Amplitude modulation am, demodulation and their circuit. Pdf telemetry applications of soqpsk and gmsk based. Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium.
Calculate the frequency deviation, modulation index, and bandwidth. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. This video tutorial has been designed to suit the curriculum of cbse class 12 students. We saw that the analysis is very similar, although applications are slightly different. There are two types of devices in which it may be necessary to the generation of amplitude modulation. 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. 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. Experiment 5 amplitude modulation preliminary discussion in an amplitude modulation am communications system, speech and music are converted into an electrical signal using a device such as a microphone. 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. 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.
Amplitude modulation, spectrum of am signal, the balanced modulator, the square law. 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. Jagannatham of iit kanpur explains the following concepts in principles of communication systemsi 1. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Complete notes download link ac notes analog communication pdf free download unit i introduction. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. 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. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio. Nagaraju associate professor r v college of engineering bangalore. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. Nptel nptel online certification course course on analog. Today we are going to study amplitude modulation, what are its uses and limitations. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Amplitude modulation we will start our study of communications systems by first analyzing the am method of communicating signals.
Lecture notes on analogue communication techniques 1. Thus, we can think of amplitude modulation as shifting the original spectrum. In early am transmitters the amplitude modulator circuit was a key element of the transmitter. Demonstration with professor sandy hill from the university of massachusetts at amherst. Linear integrated circuits amplitude modulation exam study. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. Sep 15, 20 lecture series on communication engineering by prof. Timedomain description, frequencydomain description, generation of am wave. Pdf analog communication system pdf notes ac notes sw. Chapter amplitude modulation and demodulation, ppt, adc. Amplitude modulation can be used to match audio frequencies to. In general, video modulation means that a higher frequency carrier wave is modified according to the original video signal.
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