No information is lost, but the energy is redistributed in the frequency domain. This is the simplest and oldest form of modulation. Demonstration with professor sandy hill from the university of massachusetts at amherst. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%.
Fleury navigation and communications navcom department of electronic systems. Lecture 10 introduction to amplitude modulation am. Among them, amplitude modulation am is considered the oldest. The two most common forms of amplitude modulation use either a complex carrier or a single sinusoidal carrier. Modulation is done at high power of carrier and modulating signal b. View and download powerpoint presentations on amplitude modulation and demodulation ppt.
Power amplifiers are used to boost the carrier and modulating signals before modulation d. In this lecture we will study amplitude modulation and a device which can be used as an amplitude modulator. Theory of amplitude modulation representation of am power relations in the am wave singlesideband techniques amplitude modulation. Connections between nearby logic gates have bandwidth greater than switching speed, so no line coding is needed. The original waveform amplitude is quantized with a resulting loss of information. Digital communication systems ee419 recorded lectures. Both amplitude and phase of ft carry information of ft. Modulation is a process by which the properties of one signal is made to vary the properties of another signal.
This maintains a constant recovered mt amplitude as. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Amplitude modulation early radio ee 442 spring semester. Dey, department of electrical engineering,iit bombay. 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. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures. Amplitude modulation let a in the above mentioned signal be. Surendra prasad, department of electrical engineering,iit delhi. Lecture 25 demodulation and the superheterodyne receiver. Set g so that the sinewave peaks just fall to zero.
Chapter amplitude modulation and demodulation, ppt, adc. This document is highly rated by computer science engineering cse students and has been viewed 2858 times. Pulse modulation in analog pulse modulation, the carrier is a periodic pulse train the amplitude, position and width of the carrier pulse train are varied in a continuous manner in accordance with the corresponding sample value of message 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. Questions from video lectures of nptel sl no questions video number time in minutes 1 describe the necessity of modulation in communication. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download.
Signals are variation of electrical current or voltages over time. Nptel has changed the links of pdf lecture notes since august 2019. So our focus in todays lecture will be on sinusoidal amplitude modulation in continuous time. Principles of communication systems part ii course. One can download or view all the lecture notes in pdf through the following website browse. A method of frequency translation, recovery of base band signal, amplitude modulation, spectrum of am signal, the balanced modulator, the square law.
Thus in pulse modulation, information is transmitted basically in analog form, but the transmission. The transmission bandwidth required by dsb sc is b t2b. Pdf communication systems a lecture notes by mahesh. Multiple choice questions and answers on amplitude modulation. Review of previous lectures what is modulation and why we modulate. Apr 27, 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 this video, i have explained communication system by following outlines. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio. Signals have basically three basic properties amplitude phase frequency. A typical audio frequency of 3000 hz has a wavelength of 100 km and.
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. Jagannatham received his bachelors degree from the indian institute of technology, bombay and m. Pdf analog communication system pdf notes ac notes sw. Amplitude modulation am is a modulation technique where the. Amplitude modulation and demodulation ppt xpowerpoint. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. Digital modulation 1 lecture notes ingmar land and bernard h. Lecture 10 introduction to amplitude modulation am, modulation index, envelope. Collector modulation method is high level amplitude modulation c.
Lecture notes on analogue communication techniques 1. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses. From april 07 to may 09 he was employed as a senior wireless systems engineer at qualcomm inc. 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. 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 acquisition, phaselocked loop pll, frequency division multiplexing. A percent modulation of greater than 100% is usually to be avoided. Introduction to pulse amplitude modulation, spectrum of pam signal and. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. How to download notes directly in pdf format from nptel.
Amplitude modulation we will start our study of communications systems by first analyzing the am method of communicating signals. The amplitude modulation and frequency modulation are graphically shown in. The carrier frequency, fc, should be larger than the highest spectral component. Quadrature amplitude modulation is widely used for carrying many digital signals, everything from wifi to mobile phone communications and very much more. Explain the advantages of ssb and dsbsc transmission. Lecture series on communication engineering by prof. Find powerpoint presentations and slides using the power of, find free presentations research about amplitude modulation and demodulation ppt. And what well see, in particular as we go through todays lecture, is that sinusoidal amplitude modulation, follows in a fairly straightforward way from the properties of the fourier transform that weve developed in some of the earlier lectures. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value. The dc voltage is used to automatically adjust the gain of the if amplifier in a control loop agc automatic gain control. Communication in this video tutorial, we will provide a general introduction of terms of communication systems with emphasis on wireless transmission and reception. Nptel provides elearning through online web and video courses various.