Amplitude modulation based solved problems are covered in this video lecture. Effectively it is formed by having two carriers 90 out of phase. Solutions to some sampled questions of previous finals. Commutator determines the synchronization and sequence of the channels signals to be sampled. Introduction koiters theory of amplitude modulation of the local mode is a very useful. The output modulated signal from an am modulator is. Amplitude modulation transmission by wayne tomasi as part of communications engineering topic. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Amplitude modulation theory and its application to two.
This means that their ratio is unity at the output of the adder, which forces m to a. In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique. Change in amplitude of the carrier according to modulating signal frequency. You should also see why this form of detector suffers from ripple and negative peak clipping. Principles of communication systems 20022003 8 chapter 7.
It is the standard form of digital audio in computers, cds, digital telephony and other digital audio applications. 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. Amplitude modulation definition, types, solved examples. Amplitude modulation with modulation factor 1 or 100%. These form some of the main uses of amplitude modulation. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. 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. Power amplifiers are used to boost the carrier and modulating signals before modulation d. The message signal is, for example, a function of the sound to be. Sketch the frequency domain representation of the transmitted signal and determine the bandwidth. While observing the modulation envelope, go back and adjust for the maximum. Next topic pulse code modulation pulsecode modulation pcm is used to digitally represent sampled analog signals. What is amplitude modulation, am electronics notes.
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. Amplitude modulation electronic engineering mcq questions. 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. Overmodulated am signals and its requirement for coherent detection are. The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. To obtain 50% modulation, we choose ka 1, which results in the modulated waveform of fig. Frequency modulation fm looks similar to phase modulation, though frequency is the controlled parameter, rather than relative phase. Varying these parameters in proportion to the baseband signal results in amplitude modulation am, frequency16 modulation fm, and phase modulation pm, respectively. Although its old technology, it is still widely used in the following applications. 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. The amplitude of the analog signal is sampled at uniform intervals and each sample is quantized to its nearest.
As given is the problem the modulation is sinusoidal this is also called tone modulation. Amplitude modulation an overview sciencedirect topics. At the point in time when the modulating cosine wave is zero, the total signal is a 2, so ka 0. Amplitude and phase modulation can be used together. Amplitude modulation am changes only the magnitude of the signal. The demodulation is performed by an envelope detector. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. 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. Change in amplitude of the carrier according to modulating signal b. Video solution to gate ece2006 problem amplitude modulation common data type problem.
In this chapter, let us solve a few problems based on the concept of amplitude modulation. Hence, pam is continuous in amplitude but discrete in time. If the maximum allowed frequency deviation is 50 khz. 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. What is analog modulation and state various techniques. Video solution to gate ece2006 problemamplitude 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.
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. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. With no modulation, the am carrier is transmitted by itself. 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.
Amplitude modulation theory and its application to twomode. 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 first transmission of a message using pcm was in 1943 during the world war ii. Change in amplitude of the modulating signal according to carrier signal d. Multiple choice questions and answers on amplitude modulation.
The carrier frequency, fc, should be larger than the highest spectral component. Change in frequency of the carrier according to modulating signal c. Nov 16, 2019 amplitude modulation with modulation factor 1 or 100%. By using those formulas, we can find the respective parameter values. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude. That these amplitude modulations can be demodulated using an envelope detector. This ezed video explains the solution to the following university problem the modulating signal of 20 cos2 pi 103 t is used to.
Pulse code modulation is the heart of technology in communications in todays. Amplitude modulation theory and its application to twomode buckling problems by david hui, the ohio state university, dept. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. Solutions to some sampled questions of previous finals first exam. The kind of keying were interested in refers to which characteristic of the analog carrier signal is.
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. Advantages and disadvantages of standard amplitude modulation. Collector modulation method is high level amplitude modulation c. Amplitude modulation chapter 3 objectives at the conclusion of this chapter, the reader will be able to. The square wave of unit amplitude, illustrated below.
Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Dec 11, 2017 solved numerical problems on common emitter configuration of bjt in hindi duration. In the previous chapter, we have discussed the parameters used in amplitude modulation. This deteriorates the quality of the original signal at the receiving end and causes problems in the quality of the signal. Nov 30, 2015 advantages and disadvantages of standard amplitude modulation. Find the modulation index, the carrier power, and the power required for transmitting am wave. You can publish your book online for free in a few minutes. Modulation is done at high power of carrier and modulating signal b.
Why frequency modulation is better than amplitude modulation. Heres our standard modulationdemodulation system diagram. Return the modulation amplitude to the 100% condition and reverse the xy inputs at the. This limits the applications of amplitude modulation to radios, vhf, and systems used for one to one communications only. Would 16qam be more or less susceptible to noise than this type of modulation. In this chapter, let us solve a few problems based on the concept of frequency modulation. In such case the formula for modulation index is given by.
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 amplitude modulation is called amplitude shift keying ask, when the data signal is a digital signal. That amplitude modulation uses variations in the carrier size to convey information. Calculate the frequency deviation, modulation index, and bandwidth.
The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. It requires that the amplitude of the dc a part of at is equal to the amplitude of the ac part a. The rate of change of the ask waveform baud is the same as. Mar 14, 2018 venkatesha m jrf,research scholar and adjunct faculty department of ece sai vidya institute of technology, bangalore560064. Phase modulation pm changes only the phase of the signal.
Of all the methods of impressing information onto a carrier signal, am is the oldest. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. In this problem you will know how to do power calculations and how to apply power formula in amplitude modulation. Jan 09, 2020 60 in high level amplitude modulation. Each of the chimes has an amplitude of 10v, and the carriers amplitude is 20v. There is no over modulation means that modulation index is less than or equal to 1.
What is digital modulation and state various techniques. Solved problem amplitude modulation find modulation. 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. That one way of am modulating a wave is to use a square law device such as an fet. 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. These are related to the number of levels adopted by the. The greatest noise problem in am channels is interference, noise pickup. A typical audio frequency of 3000 hz has a wavelength of 100 km and. How many am stations can be accommodated in a 100 khz bandwidth if the highest. When the modulating information signal a sine wave is applied, the carrier amplitude rises and falls in accordance. The problem of information transmission between two points is of fundamental relevance for communications. Analog communication am modulators in this chapter, let us discuss about the modulators, which generate amplitude modulated wave.1116 168 1191 421 671 30 576 1015 671 1083 1398 196 1298 1123 818 804 283 384 1074 1312 920 324 1089 1170 1061 1164 649 788 1359 417 1117 62 404