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. 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. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. These high frequencies are called carrier frequencies. A carrier wave, after being modulated, if the modulated level is calculated, then such an attempt is called as modulation index or modulation depth. What is am modulation amplitude modulation need of. These form some of the main uses of amplitude modulation. The original waveform amplitude is quantized with a resulting loss of information. The amplitude modulated wave form, its envelope and its frequency spectrum and bandwidth. 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.
Typically the modulation depth is the amplitude modulation index expressed as a percentage. Amplitude modulation am plus frequency division multiplexing fdm is one way of solving above problem. Amplitude modulation am is a modulation technique where the. Note the consistency in both amplitude and frequency. The standard form of an amplitude modulated am wave is defined by st a c 1 k a mt cos2f c t where k a is a constant called the amplitude sensitivity of the modulator. 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. This is often denoted in percentage called as percentage modulation. This chapter describes the essential principles behind. A carrier wave is highfrequency, sinusoidal signal which has a greater frequency compared to the information signal. Hapter modulation and demodulation mit opencourseware.
Selective filtering using filters with sharp cutoff characteristics. Amplitude modulation an overview sciencedirect topics. Amplitude modulation is defined as a process in which the amplitude of the carrier wave ct is varied linearly with the instantaneous amplitude of the message signal mt. In this experiment, a carrier signal and an audio modulating signal are applied to the modulator ic mc 1496 and the produced modulated waveform is observed. Fig a sinosoidal modulation signal bhigh frequency carrier c. The first discovered a method for amplifying very weak signals and basically developed the amplitude modulation technique. Note, however, that these pairs of eigenfunctions explain together the same. Here well use the example of a square law fet as illustrated in figure 9.
Each conversation is shifted to a different part of the frequency spectrum by using a highfrequency waveform to carry each individual speech signal. No information is lost, but the energy is redistributed in the frequency domain. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Simultaneous occurrence of frequency modulation with either of the two other types of modulation, as well as the simultaneous action of all three types of modulation, is treated in the theoretical part of the book. Why modulation is used suitable for signal transmission distanceetc. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. A mathematical analysis of amplitude comodulation mit. Feb 07, 2020 amplitude modulation and demodulation lab communication engineering notes edurev is made by best teachers of. To involve data information or speech information, another wave has to be imposed known as input signal above the carrier wave.
The concepts of amplitude modulation, modulation and demodulation, along with their differences is explained below. May 21, 2015 amplitude modulation notes edurev notes for is made by best teachers who have written some of the best books of. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio. This document is highly rated by students and has been viewed 514 times. Amplitude modulation and demodulation lab communication. The notes are properly synchronized and concise for much better understanding of the book. Surendra prasad, department of electrical engineering,iit delhi. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. The maximum and minimum values of the envelope of the modulated wave are represented by a max and a min respectively.
Tcom 370 notes 995 modulation and demodulation modems for. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. 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. We decided to construct our spectrograms using mtm harmonic analysis e. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Amplitude modulation circuit implementation for use in a communication. May 05, 2019 am modulation amplitude modulation is the technique in which the amplitude of carrier wave varies with the variation in the frequency and amplitude of information 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. Nov 14, 2016 when the amplitude of high frequency carrier wave is changed in accordance with the intensity of the signal, the process is called amplitude modulation. Mar 17, 2020 this is the summary notes of the important terms and concepts in chapter 5 of the book electronic communications system by wayne tomasi. It states the level of modulation that a carrier wave undergoes. Modulation techniques 32 amplitude shift keying ask values represented by different amplitudes of carrier usually, one amplitude is zero i.
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. Immunity of angle modulation to nonlinearities very useful feature of angle modulation is its constant amplitude, which makes it less susceptible to nonlinearities amplifier with second order nonlinear distortion clearly, the first term is the desired signal amplification term, the remaining terms are the unwanted nonlinear distortion. Amplitude modulation early radio ee 442 spring semester. Winter 2003 uw, ece 318 lecture notes 7 amplitude modulation am ch. Effectively it is formed by having two carriers 90 out of phase. Lecture series on communication engineering by prof. In this article, you will find the study notes on types of modulation and demodulation which will cover the topics such as introduction to communication systems, amplitude and demodulation, classification of am, angle modulation and demodulation, generation of fm and pulse modulation. 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.
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. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Essentially an amplitude modulated wave consists of a radio frequency carrier a sine wave at one frequency, typically in the radio frequency portion of the spectrum. Design and implementation of amplitude modulator and demodulator introduction communication is the most important needs from the very beginning of civilization. Demonstration with professor sandy hill from the university of massachusetts at amherst. It is the extent of modulation denoted in percentage, and is denoted by m. Theory of amplitude modulation brainkart lecture notes. The basic theory and equations behind amplitude modulation are relatively straightforward and can be handled using straightforward trigonometric calculations and manipulation. Principles of amplitude modulation brainkart lecture notes.
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. Senior member of technical staff, mit lincoln laboratory. The amplitude modulation am modulation depth figure is complementary to the modulation index. The amplitude of an audio carrier signal can be modulated by another modulator signal, either by simple multiplication ring modulation or by adding a timevarying modulating signal to a constant signal dc offset before multiplying it with the carrier signal amplitude modulation. For a perfect modulation, the value of modulation index should be 1, which means the modulation depth should be 100%. 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.
Amplitude modulation is a fluctuating noise a noise level rising and falling in a. Amplitude modulation am, demodulation and their circuit. This is done in order to show that an amplitude limiter can be used suc. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Wave modulation and breakdown airsea interaction laboratory. View amplitude modulation research papers on academia. Modulationtypesamplitude,frequency,phase modulation. The standard form of an amplitude modulated am wave is defined by. Pdf on the combining of the amplitude and phase modulation in. Process by which a property or a parameter of a signal is varied in proportion to a second signal. Amplitude modulation notes edurev notes for is made by best teachers who have written some of the best books of. This process of imposing an input signal on a carrier wave is known as modulation.
There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. Recall that our goal is to transmit data over a commu nication link, which we achieve by mapping the. Department of electronics and communication engineering. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. There are no amplitude scales shown, but you should be able to deduce the depth. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. The first transmission however, was performed by fessenden in 1906 from brant rock, massachusetts. His knowledge of advanced mathematical spectral analysis techniques is quite impressive. What is amplitude modulation, am electronics notes. This is the summary notes of the important terms and concepts in chapter 5.
Amplitude modulation is the changing the amplitude of the carrier signal with respect to the instantaneous change in message signal. Subsequent workers in the field have used rectification and lowpass filtering of the surface displacement to provide a measure of amplitude modulation, and zero. Much of the data analysis relating to wave stability has depended on. Learn the concise history of amplitude modulation or am broadcasting technique. When the amplitude of high frequency carrier wave is changed in accordance with the intensity of the signal, the process is called amplitude modulation.
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 defined as a process in which the amplitude of the carrier wave ct is varied linearly with the instantaneous amplitude of the message signal mt. Winter 2003 uw, ece 318 lecture notes 1 amplitude modulation part 1 instructor. Review pulse train bandwidth s ingle pulse of duration. The pulse may take any real voltage value that is proportional to the value of the original waveform. Notes for electronics engineering pdf ppt 05012017 dhirendra yadav 0 comments 4. Amplitude modulation or am is a method to transmit signals via electromagnetic transmission. Amplitude modulation can be produced in various ways. 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. Amplitude modulation communication systemclass 12 physics. This gives us something to modulate and carry the information pattern from.
1486 563 1281 614 843 1171 708 1452 1338 532 1072 592 257 56 200 801 696 404 596 411 1157 347 153 1213 1200 372 1247 101 1024 443 1015 874 362