Bandpass modulation and demodulation techniques communication systems, dept. Amplitude modulation definition, types, solved examples. Introduction to quadrature carrier modulation qcm and demodulation of qcm. Amplitude modulation qam 4 ee4900ee6720 digital communications suketu naik quadratureamplitude modulation qam applications qam rhymes with guam and vietnam is commonly used in communications example1. The term demodulator is used because the demodulation process is considered to be the opposite of modulation. In order to understand the concept of asynchronous demodulation consider the two amplitude modulated signals illustrated. 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. Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission than frequency shift keying, a form of frequency modulation. 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 practice, the demodulation of suppressed carrier amplitude modulated signals requires fairly. Vsb signals are generated using standard am or dsbsc modulation, then passing modulated signal through a sideband shaping.
To generate and demodulate an amplitude shift keyed ask signal and a binary fsk signal. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. At the receiving end the signal is being demodulated to get the original data. Restoring or recovering the message signal from the received. What is the maximum efficiency of ordinary amplitude modulated am. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. Here well use the example of a square law fet as illustrated in figure 9. The process of amplitude modulation consists of the amplitude of the carrier wave being varied in sympathy with a modulating signal. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is.
When expressed as a percentage it is the same as the depth of modulation. A product modulator is used for generating the modulated signal as shown in figure 3. Chapter amplitude modulation and demodulation, ppt, adc. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. Am modulation and demodulation part 1 this video uses properties of the fourier transform to explain modulation and demodulation inside a simple am radio.
So if you just start seeing communication there is in a way two types. In this lecture we will cover continuoustime modulation. Then we discussed amplitude modulation in detail including generation of am signals as well as demodulation of am signals. Both phase and frequency of carrier are known at the demodulator amplitude of carrier is not important since it in. Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. A modem is an equipment that performs both modulation and demodulation. Amplitude modulation early radio ee 442 spring semester. Read online modulation d amplitude demodulation d amplitude book pdf free download link book now. 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. And, we were agreed that in a demodulation process could be very similar to the modulation process, the received. To study sampling and reconstruction of pulse amplitude modulation system 6. 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. 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. Vsb modulation with envelope detection is used to modulate image in analog tv signals.
Bookmark file pdf amplitude modulation tutorial solutions funda in this video, i have explained am examples on multi tone am signals by following outlines. In practice, problems arise in baseband transmissions, the major cases being. Principles of communication part i professor aditya k. Amplitude modulation contents slide 1 amplitude modulation slide 2 the envelope and no overmodulation slide 3 example for single tone modulation slide 4 measuring the modulation index slide 5 transmitted vs.
Analog modulation and demodulation amplitude modulation pages 306309. Quadrature amplitude modulation qam is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. This document is highly rated by computer science engineering cse students and has been viewed 2848 times. We will discuss communication applications, such as frequencydivision multiplexing and singleside band modulation. Message power in st slide 6 powers in single tone case cont. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. Lecture notes on analogue communication techniques 1. Communication systems a lecture notes by mahesh lohith k. Apr, 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.
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. This is the simplest form of modulation where the amplitude of the carrier wave is modulated by the analog signal known as. Demodulator and the signal space projections constellation points. Modulation techniques for mobile communication nptel. A c m a x r t for a sinusoidal modulating signal, it is given by. We will use the basic demodulation approach with full rectification and low pass filter followed by a dc removal. The demodulation is performed by an envelope detector. 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. Overmodulated am signals and its requirement for coherent detection are also considered. The two most common forms of amplitude modulation use either a complex carrier or a single sinusoidal.
The message signal is, for example, a function of the sound to be reproduced by a. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. Analog signal such as voice or music is converted to discrete samples and then quantized to bits. This equation represents double amplitude modulation. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation.
Amplitude modulation can be produced in various ways. Demodulation uses either standard am or dsbsc demodulation, depending on whether a carrier tone is transmitted. Lecture series on communication engineering by prof. Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. 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 is a modulation technique where the. Introduction to modulation and demodulation the purpose of a communication system is to transfer information from a source to a destination. Amplitude modulation double side band nptel mafiadoc. Download modulation d amplitude demodulation d amplitude book pdf free download link or read online here in pdf.
That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. A method of frequency translation, recovery of base band signal, amplitude modulation, spectrum of am signal, the balanced modulator, the square law demodulator, dsbsc, ssbsc and vsb, their methods of generation and demodulation, carrier. Using the absolute value, filter, and acdc estimator vi functions, implement the demodulation of am signal to on the same modulation. The amplitude modulation and frequency modulation are graphically shown in. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. This gives us something to modulate and carry the information pattern from. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Unit 4 week3 power efficiency, dsbsc modulation and. So if i wish to do that what i can do is something like this i can first modulate the signal or even demodulation also similar thing will be happening so i can put it into.
The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. It conveys two analog message signals, or two digital bit streams, by changing modulating the amplitudes of two carrier waves, using the amplitude shift keying ask digital modulation. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. There are no amplitude scales shown, but you should be able to deduce the depth. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted.
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