Multiple choice questions and answers on amplitude modulation. The carrier frequency, fc, should be larger than the highest spectral component. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. Amplitude modulation is a linear process, hence the principle of superposition applies. Fm modulated signal st is a nonlinear function of the modulating signal mt, thus it is known as nonlinear modulation process. 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. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising.
Frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt. Application the process of varying amplitude of the highfrequency or carrier wave in accordance with the intelligence code, voice or music to be transmitted, keeping the frequency and phase of the carrier wave unchanged, is known as the amplitude modulation. 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. Principles of communication systems 20022003 8 chapter 7. Quadrature amplitude modulation qam transmitter is the property of its rightful owner. Vary the frequency and amplitude of the modulating. Because of the low cost of the parts necessary to implement am transmission and the simplicity of the underlying technology, using amplitude modulations is a cheap and effective way to perform many tasks that require wireless communication.
This is the same as the am modulation above but without the carrier. Chapter 5 amplitude modulation am, ppt, adc, semester. If so, share your ppt presentation slides online with. Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Principles of communication modulation a signal can be anything like a sound wave which comes out when you shout. Each part may be of any convenient amplitude at the input to an adder.
Amplitude modulation am radio is a commonplace technology today, and is standard in any type of commercial stereo device. This principle is at the heart of amplitude modulation. The idea is simple, though the notion that it can be used to modulate signals. Amplitude modulation am is an analog modulation scheme where the amplitude a of a fixedfrequency carrier signal is continuously modified to represent data in a message. This is further divided into frequency and phase modulation. No information is lost, but the energy is redistributed in the frequency domain. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier. What is amplitude modulation, am electronics notes. Collector modulation method is high level amplitude modulation c.
In commercial tv transmission in india, picture and speech signals are. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. Changing the amplitude of the carrier am modulation is one type of modulation easy, cheap, lowquality used for am receiver and cbs citizen bands. Each of these is one bit of information, 0s and 1s.
To heterodyne means to mix to frequencies together so as. Bandpass noise referring to the communication system diagram below, xt. 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. The frequency of the carrier signal is usually much greater than the highest frequency of the input message signal. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. 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. Demonstration with professor sandy hill from the university of massachusetts at amherst. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. The pulse may take any real voltage value that is proportional to the value of the original waveform. 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. Amplitude modulation transmission by wayne tomasi as part of communications engineering topic.
The message signal is, for example, a function of the sound to be reproduced by a. Amplitude modulation am changes only the magnitude of the signal. Ppt quadrature amplitude modulation qam transmitter. Because of these relationships the pdf of the envelope is rayleigh. This is a carrier symbol that represents one information bit. Am modulation in order to transfer signals we need to transfer the frequency to higher level one approach is using modulation modulation. Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission than frequency shift keying, a form of frequency modulation. Amplitude modulation early radio ee 442 spring semester. It states the level of modulation that a carrier wave undergoes.
Accordingly it is worth looking at some of the disadvantages of amplitude modulation. There are no amplitude scales shown, but you should be able to deduce the depth. Amplitude modulation is a modulation system where the carrier wave. The two common forms of analog modulation are amplitude modulation. Principles of communication modulation tutorialspoint. Amplitude modulation or am as it is often called, is a form of modulation used for radio transmissions for broadcasting and two way radio communication applications. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Transmitter modifies the message signal into a form which is suitable for transmission over channel which is achieved by modulation information source. A typical audio frequency of 3000 hz has a wavelength of 100 km and. Types of amplitude modulation am double sideband with carrier we will call it am. 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. The original waveform amplitude is quantized with a resulting loss of information. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm.
Modulation is the process of varying one or more properties of a highfrequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted. A free powerpoint ppt presentation displayed as a flash slide show on id. Frequency modulation fm looks similar to phase modulation, though frequency is the controlled parameter, rather than relative phase. The basic theory and equations behind amplitude modulation are relatively straightforward and can be handled using straightforward trigonometric calculations and manipulation. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. The output spectrum may be found by considering each component cosine wave in mt separately and summing at the output. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. In the frequency domain, amplitude modulation corresponds to translating the baseband spectrum to a band. Phase modulation pm changes only the phase of the signal. This is the most widely used type of am modulation. Frequency modulation is the process of varying the frequency of the carrier signal linearly with the message signal. A carrier wave, after being modulated, if the modulated level is calculated, then such an attempt is called as modulation index or modulation depth.
Qam modulation is a combination of amplitude shift keying and phase shift keying, both carrier wave is modulated by changing both its amplitude and phase. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Amplitude modulation modulation frequency modulation. Amplitude and phase modulation can be used together. Hsu analog and digital communication summary equation message general mt monotone am cos.
It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Amplitude modulation introduction amplitude modulation is the simplest and earliest form of transmitters am applications include broadcasting in medium and highfrequency applications, cb radio, and aircraft communications basic amplitude modulation the information signal varies the instantaneous amplitude of the carrier am characteristics am is a nonlinear process sum and. What is communication transmitter channel receiver a communication system. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Commutator determines the synchronization and sequence of the channels signals to be sampled.
In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Ppt amplitude modulation powerpoint presentation free. Jun 17, 2018 in this video, i have explained amplitude modulation by following outlines. 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. Using amplitude modulation to shift the baseband signal fm radio 88mhz108 mhz. Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal. The output spectrum may be found by considering each component cosine wave in. Quadrature amplitude modulation qam pam signals occupy. The maximum and minimum values of the envelope of the modulated wave are represented by a max and a min respectively. 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. Chapter amplitude modulation and demodulation, ppt, adc, semester, engineering notes for computer science engineering cse is made by best teachers who have written some of the best books of computer science engineering cse.
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. Quadrature amplitude modulation qam pam signals occupy twice the bandwidth required for the baseband transmit two pam signals using carriers of the same frequency but in phase and quadrature demodulation. Note that the modulated signal envelope corresponds to the wave form of the dsb am modulating signal. Each radio station is assigned 200 khz, to transmit a stereo audio. 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. The amplitudemodulated wave may be described by the following formula.
In amplitude modulation, it is the voltage level of the signal to be transmitted. Quadrature amplitude modulation linkedin slideshare. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio. Amplitude modulation is a very basic form of modulation, and although its simplicity is one of its major advantages, other more sophisticated systems provide a number of advantages. 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. Amplitude modulation is mostly used in the form of electronic communication. Why modulation is used suitable for signal transmission distanceetc. Hapter modulation and demodulation mit opencourseware. Amplitude modulation ang man shun october 30, 2012 reference hwei p.
Power amplifiers are used to boost the carrier and modulating signals before modulation d. Ppt amplitude modulation powerpoint presentation free to. Pulse width modulation and in position ppm, pulse position. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn. Apr 10, 2018 amplitude modulation am contents hide 1. This shout can be heard only up to a certain distance. In communications, the analog signal shape, by preagreed convention, stands for a certain number of bits and is called a symbol. It can be achieved in a number of ways, but the simplest. Amplitude modulation an overview sciencedirect topics.
Amplitude modulation definition, types, solved examples. Amplitude, frequency and phase modulation can be applied directly by software to the generated signals, which gives great flexibility where complicated and precise waveforms are required. There are a variety of modulation schemes available for both analog and digital modulation. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation.
Amplitude modulation amplitude modulation amplitude modulation is a process where the amplitude of a carrier signal is altered according to information in a message signal. Scribd is the worlds largest social reading and publishing site. Modulation is done at high power of carrier and modulating signal b. Frenzeljr, in handbook of serial communications interfaces, 2016. The modulation index can be used to make the carrier amplitude more or less sensitive to the variations in the value of the baseband signal. Amplitude modulation and demodulation, ppt, adc, semester, engineering computer science engineering cse notes edurev is made by best teachers of computer science engineering cse. Quadrature amplitude modulation qam pam signals occupy twice the bandwidth required for the baseband transmit two pam signals using carriers of the same frequency but in. Although one of the earliest used forms of modulation it is still used today, mainly for long, medium and short wave broadcasting and for some aeronautical point to point. The singlesided spectrum of the modulated signal replicates the baseband. Amplitude modulation corresponds to multiplying the carrier by the shifted baseband signal. In fact, all radio channels in the am band use this type of modulation.
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