Amplitude modulation am is the technique in which the amplitude peaktopeak voltage of the carrier wave is varied as a function of time in proportion to the strength of the data signal. In the previous chapter, we have discussed the parameters used in amplitude modulation. Varying these parameters in proportion to the baseband signal results in amplitude modulation am, frequency16 modulation fm, and phase modulation pm, respectively. With no modulation, the am carrier is transmitted by itself. In this problem you will know how to do power calculations and how to apply power formula in amplitude modulation. Return the modulation amplitude to the 100% condition and reverse the xy inputs at the.
You can publish your book online for free in a few minutes. Frequency modulation fm looks similar to phase modulation, though frequency is the controlled parameter, rather than relative phase. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Amplitude and phase modulation can be used together.
Each of the chimes has an amplitude of 10v, and the carriers amplitude is 20v. Nov 16, 2019 amplitude modulation with modulation factor 1 or 100%. Power amplifiers are used to boost the carrier and modulating signals before modulation d. Overmodulated am signals and its requirement for coherent detection are. The square wave of unit amplitude, illustrated below. Collector modulation method is high level amplitude modulation c. To obtain 50% modulation, we choose ka 1, which results in the modulated waveform of fig. The message signal is, for example, a function of the sound to be. This limits the applications of amplitude modulation to radios, vhf, and systems used for one to one communications only. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. The amplitude modulation is called amplitude shift keying ask, when the data signal is a digital signal. Calculate the frequency deviation, modulation index, and bandwidth. This means that their ratio is unity at the output of the adder, which forces m to a. Multiple choice questions and answers on amplitude modulation.
Analog communication am modulators in this chapter, let us discuss about the modulators, which generate amplitude modulated wave. Amplitude modulation transmission by wayne tomasi as part of communications engineering topic. 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. These are related to the number of levels adopted by the. Hence, pam is continuous in amplitude but discrete in time. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. The demodulation is performed by an envelope detector. What is digital modulation and state various techniques. What is amplitude modulation, am electronics notes. Solved problem amplitude modulation find modulation. Why frequency modulation is better than amplitude modulation. Video solution to gate ece2006 problem amplitude modulation common data type problem.
This ezed video explains the solution to the following university problem the modulating signal of 20 cos2 pi 103 t is used to. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. Next topic pulse code modulation pulsecode modulation pcm is used to digitally represent sampled analog signals. Commutator determines the synchronization and sequence of the channels signals to be sampled. Amplitude modulation an overview sciencedirect topics. That one way of am modulating a wave is to use a square law device such as an fet. The problem of information transmission between two points is of fundamental relevance for communications. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. By using those formulas, we can find the respective parameter values. Heres our standard modulationdemodulation system diagram. 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. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation.
Mar 14, 2018 venkatesha m jrf,research scholar and adjunct faculty department of ece sai vidya institute of technology, bangalore560064. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. 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. Amplitude modulation electronic engineering mcq questions. Amplitude modulation chapter 3 objectives at the conclusion of this chapter, the reader will be able to. Find the modulation index, the carrier power, and the power required for transmitting am wave. Slide 3 discretetime fm modulator slide 4 single tone fm modulation.
Would 16qam be more or less susceptible to noise than this type of modulation. Change in frequency of the carrier according to modulating signal c. Amplitude modulation systems are susceptible to noise generation. You should also see why this form of detector suffers from ripple and negative peak clipping. Ook carrier is either on or off fsk 2 different frequencies shown bpsk 2 symbols with same amplitude and frequency, but different phases qpsk 4 symbols with same amplitude and frequency, but different phases. The term keying is the legacy term from the times of telegraphy, when an operator would manually push keys to make short and long tones.
Nov 30, 2015 advantages and disadvantages of standard amplitude modulation. The carrier frequency, fc, should be larger than the highest spectral component. The greatest noise problem in am channels is interference, noise pickup. Amplitude modulation with modulation factor 1 or 100%. The kind of keying were interested in refers to which characteristic of the analog carrier signal is. Amplitude modulation theory and its application to twomode buckling problems by david hui, the ohio state university, dept. In this chapter, let us solve a few problems based on the concept of frequency modulation. When the modulating information signal a sine wave is applied, the carrier amplitude rises and falls in accordance. These form some of the main uses of amplitude modulation. The first transmission of a message using pcm was in 1943 during the world war ii.
In amplitude modulation, it is the voltage level of the signal to be transmitted that changes the amplitude of the carrier in proportion, see figure 63. The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. 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. Amplitude modulation based solved problems are covered in this video lecture. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Phase modulation pm changes only the phase of the signal. How many am stations can be accommodated in a 100 khz bandwidth if the highest. Introduction koiters theory of amplitude modulation of the local mode is a very useful.
It requires that the amplitude of the dc a part of at is equal to the amplitude of the ac part a. If the maximum allowed frequency deviation is 50 khz. It is a modulation system in which the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the signal at the instant of sampling. A typical audio frequency of 3000 hz has a wavelength of 100 km and.
In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique. Advantages and disadvantages of standard amplitude modulation. In such case the formula for modulation index is given by. 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. 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. At the point in time when the modulating cosine wave is zero, the total signal is a 2, so ka 0. The output modulated signal from an am modulator is. Pulse code modulation pcm was pioneered by the british engineer alec reeves in 1937. Amplitude modulation definition, types, solved examples. Pulse code modulation is the heart of technology in communications in todays. Of all the methods of impressing information onto a carrier signal, am is the oldest. Jan 09, 2020 60 in high level amplitude modulation.
Effectively it is formed by having two carriers 90 out of phase. 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. 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 the allocated range it is unacceptable because it causes severe interference with other stations and causes a loud splattering sound. It is the standard form of digital audio in computers, cds, digital telephony and other digital audio applications. Solutions to some sampled questions of previous finals first exam. The amplitude of the analog signal is sampled at uniform intervals and each sample is quantized to its nearest. Amplitude modulation theory and its application to twomode. Video solution to gate ece2006 problemamplitude modulation. While observing the modulation envelope, go back and adjust for the maximum. Change in amplitude of the carrier according to modulating signal frequency. Change in amplitude of the carrier according to modulating signal b.
That amplitude modulation uses variations in the carrier size to convey information. Solutions to some sampled questions of previous finals. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the. Modulation is done at high power of carrier and modulating signal b. What is analog modulation and state various techniques. 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. 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. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. This deteriorates the quality of the original signal at the receiving end and causes problems in the quality of the signal. Dec 11, 2017 solved numerical problems on common emitter configuration of bjt in hindi duration. Although its old technology, it is still widely used in the following applications. That these amplitude modulations can be demodulated using an envelope detector. As given is the problem the modulation is sinusoidal this is also called tone modulation.
Ssb modulation and am wave systems problems solutions what students are saying as a current student on this bumpy collegiate pathway, i stumbled upon course hero, where i can find study resources for nearly all my courses, get online help from tutors 247, and even share my old projects, papers, and lecture notes with other students. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Frequency modulation examplesproblems 1 a music signal with frequency components from 50 hz to 2 hz is frequency modulated. Decision maker preparation generation 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 1. Principles of communication systems 20022003 8 chapter 7.
Amplitude modulation am changes only the magnitude of the signal. Sketch the frequency domain representation of the transmitted signal and determine the bandwidth. 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. In this chapter, let us solve a few problems based on the concept of amplitude modulation. The rate of change of the ask waveform baud is the same as.
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