Lecture notes in amplitude modulation, it is common practice to express the degree to which a carrier is modulated as a percentage of modulation. In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique. The information is carried by a signal, which is certain physical quantity that changes with time. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Course material lecture notes unit i fundamentals of analog communication introduction in the microbroadcasting services, a reliable radio communication system is of vital. The focus of this chapter is amplitude modulation am. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio.
There are no amplitude scales shown, but you should be able to deduce the depth. Pdf amplitude modulation fundamentals semantic scholar. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In modulation, the message signal changes the amplitude, frequency, or phase of the carrier signal. If you continue browsing the site, you agree to the use of cookies on this website. Chapter05 fundamentals of frequency modulation by frenzel jr. In the modulation process, the baseband voice, video, or digital signal modifies another, higherfrequency signal called the carrier, which is usually a sine wave. Modulation for analog new york university tandon school. The two most common forms of amplitude modulation use either a complex carrier or a single sinusoidal carrier.
Amplitude modulation early radio ee 442 spring semester. Demodulation uses either standard am or dsbsc demodulation, depending on whether a carrier tone is transmitted. There is another way of modulating a, sinusoidal carrier wave, namely, angle modulation in which the angle of the carrier wave is varied according to the baseband signal. Amplitude modulation transmission by wayne tomasi as part of communications engineering topic. The left and right channels each limited to 15khz are multiplexed into a single baseband signal using amplitude modulation using frequency modulation to shift the baseband. The signal can be a voltage proportional to the amplitude of the voice. This is the summary notes of the important terms and concepts in chapter 4 of the book electronic communications system by wayne tomasi. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. 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. This part of the lab will demonstrate the use of an ota op amp to provide low level amplitude modulation.
Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. 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. This principle is at the heart of amplitude modulation. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Amplitude modulation is a modulation system in which the carrier wave has its instan taneous.
Basic question bank with answers and explanations transcribed 2007 09 28 by donn va7dh from exhaminer. Vector modulation and frequency conversion fundamentals john hansen, agilent technologies. Amplitude modulation am is a modulation technique where the. When the am signal is displayed on an oscilloscope.
Vmax vmin vmin pp 0 vmax pp to compute the modulation index from measurements taken on the composite modulated wave itself. Amplitude modulation chapter 3 objectives at the conclusion of this chapter, the reader will be able to. However, it is more common amplitude modulation fundamentals 97 figure 35 an am wave showing peaks vmax and troughs vmin. Amplitude modulation am changes only the magnitude of the signal. We note that for ordinary am modulation, if the modulation percentage %100. Vector modulation and frequency conversion fundamentals. The amplifiers you studied in fundamentals had a constant voltage or power gain, and only one input this one has two. A fundamental characteristic of an fm signal is that the frequency deviation f. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Principles of communication systems 20022003 8 chapter 7. Vsb modulation with envelope detection is used to modulate image in analog tv signals. Phase modulation pm changes only the phase of the signal.
In this video, i have explained amplitude modulation by following outlines. These laboratory note are reproduced in part from the labvolt. Unit i fundamentals of analog communication get my notes. To study different amplitude modulation scheme to study generation and detection of am signals to study application of am double sideband suppressed carrier dsbsc modulation double sideband large carrier dsblc modulation. Amplitude modulation fundamentals free download as powerpoint presentation. Amplitude modulation fundamentals modulation detector.
Analog communication pdf notes basic concepts, frequency modulation. The second part of this note therefore presents the fundamentals. Note that this is the addition of two parts, a dc term and an ac term. Note that for m1 modulation percentage of 100 percent. Telecommunications basics the purpose of any telecommunications system is to transfer information from the sender to the receiver by a means of a communication channel. The time dependence of its projection onto the real axis gives the signal strength as drawn to the right of the corresponding phasor diagram. In the case of amplitude modulation am, the modulated oscillation vector is always in phase with the carrier field while its length oscillates with the modulation frequency. This document is highly rated by electronics and communication engineering ece students and has been viewed 441 times.
Overmodulation overmodulation is a condition that occurs when an excessive intelligence signal overdrives an am modulator making %m 100% because e i e c modulated carrier amplitude reach value greater than double of unmodulated value it produces a distortion known as sideband splatter, which results on transmission at frequencies outside. We can choose the signal constellation such that the amplitude is the same for all signal alternatives, by placing the signal vectors on a circle in the signal space. In am modulation the carrier signal changes almost linearly according to. Each radio station is assigned 200 khz, to transmit a stereo audio. The equations for the simple example of the a single tone used for modulation can be expanded to show how the signal will appear of a typical sound consisting of many frequencies is used to modulated the carrier. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Changing the amplitude of the carrier am modulation is one type of modulation easy, cheap, lowquality. Amplitude and phase modulation can be used together. This chapter describes the essential principles behind. Three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Frequency modulation fm looks similar to phase modulation, though frequency is the controlled parameter, rather than relative phase.
The message signal is, for example, a function of the sound to be reproduced by a. John v yelland ma dphil oxon minstp fiet amasa mioa. Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Lecture notes on analogue communication techniques 1. Amplitude modulation, spectrum of am signal, the balanced modulator, the square law. 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. Winter 2003 uw, ece 318 lecture notes 7 amplitude modulation am ch.
Inwg work package 1 fundamentals of am 11 nov 2015. Amplitude modulation fundamentals 95 figure 32a simplified method of representing an am highfrequency sine wave. Vsb signals are generated using standard am or dsbsc modulation, then passing modulated signal through a sideband shaping. Percentage of modulation the modulation index can be determined by measuring the actual values of the modula tion voltage and the carrier voltage and computing the ratio. Commutator determines the synchronization and sequence of the channels signals to be sampled. Apr 10, 2020 amplitude modulation electronics and communication engineering ece notes edurev is made by best teachers of electronics and communication engineering ece. Hapter modulation and demodulation mit opencourseware. Sound transmission in air has limited range for the amount of power. Spectrum analyzer driverinterface circuit is the modulation level at 50% as calculated from the frequency domain display and is the inband second order product at an acceptable level. Amplitude modulation we will start our study of communications systems by first analyzing the am method of communicating signals. You will be using this identity a lot 6 suppose that t is a constant or slowly varying, then the cos t appears as a xed or time varying attenuation factor even a slowly varying attenuation can be very detrimental from a. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave.
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