Download modulation d amplitude demodulation d amplitude book pdf free download link or read online here in pdf. Read online modulation d amplitude demodulation d amplitude book pdf free download link book now. We will discuss these two types of detectors in this experiment. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%.
An amplitude modulated signal is composed of both low frequency and high. By the amplitude shift keying theory, we can understand the process of ask technique. In practice, the demodulation of suppressed carrier amplitude modulated signals requires fairly. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. The modulation processisprobablyeasier tounderstand whenviewed fromthe perspective of amplitude modulation. Amplitude modulation and demodulation using matlab functions. Phase modulation pm is a different form of frequency modulation and the carrier is similar in appearance to a frequencymodulated carrier. Keying is indicating the transmission of digital signal over the channel. Pdf on amplitude and frequency demodulation using energy. Once a signal has been modulated, information is retrieved through a demodulation process.
Amplitude modulation is defined as a process in which the amplitude of the carrier. If not, what is the default depth of modulation for am here. Demonstrate understanding of various amplitude modulation and demodulation techniques. The process of demodulation for signals using amplitude modulation can be achieved in a number of different techniques, each of which has its own advantage. Let us examine the spectrum of the demodulated dsbsc signal. Amplitude modulation is a modulation system in which the carrier wave has its instan taneous. 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. Matlab code for amplitude modulation am file exchange. Amplitude modulation am is a modulation technique where the. This experiment examines the characteristics of the amplitude modulation am.
Modulation damplitude demodulation damplitude pdf book. 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. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam to design the simulink model of the dsbam to analyze each signal in time and frequency domains using time scope and spectrum analyzer. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Normally detector can be classified as synchronous detector and asynchronous detector. Demodulation of pam wave for demodulation of the pulse amplitude modulated signal, pam is fed to the low pass filter. Hi, im a beginner in matlab and im just wondering whether the modulation constant. Amplitude modulation and demodulation 1 lab notes a word about power. To study pulse amplitude modulation and demodulation. The amplitude of the high frequency carrier of the signal is. Amplitude modulation theory frequency spectrum power.
Amplitude modulation, modulators, and demodulators ese. In practice, the carrier may be highfrequency hf while the modulation is audio. This is the same as the am modulation above but without the carrier. Note that this is on the very low end of the recommended voltage range. All books are in clear copy here, and all files are secure so dont worry about it. Introduction to modulation and demodulation free download as powerpoint presentation. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309.
Report and explain the voltage values in the time domain and the frequency. To study amplitude demodulation by linear diode detector 3. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. There are two reasons why frequencydivision multiplexing works. For the example above, the carrier signal is p es cos2. In this lab, students investigate two methods to recover an amplitude modulation am signal in order to develop an understanding of the demodulation process in the time and frequency domain.
Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. First, students will generate an am signal using data from a file, and then they will use the envelope detector method to recover the original message by connecting the am signal to a rectifier and the. To generate amplitude modulated wave and determine the percentage modulation. In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. Fig a sinosoidal modulation signal bhigh frequency carrier c. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. 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. Am modulation and demodulation part 1 this video uses properties of the fourier transform to explain modulation and demodulation inside a simple am radio. To study and perform frequency modulation and demodulation. 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.
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. Modulation and demodulation pdf on the various aspects of modulation and demodulation. Laboratory manual principles of communication system lab ee226f ivth semester. Introduction to modulation and demodulation modulation. It is still in use today in a variety of systems, including, of course, am broadcast radio. From experiment 3, we know that the amplitude modulation signal utilizes the amplitude of audio signal to modulate high frequency carrier signal.
The spectral efficiency of the transmitted ask waveform is also a consideration and the m. Amplitude modulation contents slide 1 doublesideband suppressedcarrier amplitude modulation slide 2 spectrum of a dsbscam signal slide 3 why called doublesideband slide 4 ideal coherent receiver slide 5 coherent receiver analysis slide 6 spectra in dsbscam system slide 7 demodulator using the preenvelope slide 8 costas loop demodulator. To see what your fm radio receives, try using values such as are used for commercial fm transmission 88 108 mhz. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example.
The amplitude modulated wave form, its envelope and its frequency spectrum and bandwidth. Amplitude modulation and demodulation electrical and computer. The idea is simple, though the notion that it can be used to modulate signals. As before, this may require a manual adjustment of the voltsdiv and. If we were to implement every possible combination of demodulation algorithm, carrierrecovery technique, and clock regeneration as a distinct model, the combinatorial explosion of different models would become unmanageable. Qam is composed of two independent pulse amplitude modulation pam baseband modulations placed on. Multiple choice questions and answers on amplitude 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. Amplitude modulation or am is a method to transmit signals via electromagnetic transmission. Theory shows that in order to transmit a wave effectively, the length of the.
Amplitude modulationdemodulation in matlab file exchange. Bookmark file pdf amplitude modulation tutorial solutions funda in this video, i have explained am examples on multi tone am signals by following outlines. Amplitude modulation is one way of transmitting radio signals across large distances. To study frequency modulation and determine its modulation factor 4. I ntroduction an amplitude modulated signal is composed of both low frequency and high frequency components. The process of amplitude modulation consists of the amplitude of the carrier wave being varied in sympathy with a modulating signal. This type of modulation comes under digital modulation schemes.
Any baseband signal can be broken up into a weighted sum of sinusoids using fourier decomposition chapter. Since amplitude modulation signal utilizes audio signal to modulate carrier signal. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam. Amplitude modulation is the process of varying the amplitude of a carrier wave in proportion to the amplitude of a baseband signal. Amplitude modulation is widely used in aviation because am is not subject to the capture effect. Chapter 6 doublesideband suppressedcarrier amplitude. Each channel sharing scheme a set of basis vectors. Amplitude modulation definition, types, solved examples. In frequency modulation, the amplitude of the carrier. This chapter describes the essential principles behind modulation and demodulation, which we introduced briefly in chapter. In this project, we will use the matlab to simulate the conditions of ams immunity to the capture effect. Overmodulated am signals and its requirement for coherent detection are also considered.
To study and perform amplitude modulation and demodulation. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. An am wave may thus be dscribed, in the most general form, as a function of time as follows.
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. The low pass filter eliminates high frequency ripples and generates the demodulated signal which has its amplitude proportional to pam signal at all time instant. Department of electronics and communication engineering. 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. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Oct 30, 2017 amplitude modulation and demodulation. The term demodulator is used because the demodulation process is considered to be the opposite of modulation. Amplitude modulation corresponds to multiplying the carrier by the shifted baseband signal. The wavelets are founded on rigorous mathematical theory, and the expansions are robust. Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. What we do in am, very roughly,is to throw away the frequency content of.
On amplitude and frequency demodulation using energy operators. Amplitude modulation am is an analog modulation scheme where the amplitude a of. The meaning of source coding is the conversion from analog. Mar 28, 2018 matlab code for amplitude modulation and demodulation using functions ammod and amdemod. The code for amplitude modulation am with control of modulation index ma has been developed using matlab according to conventional theory. In this system we have a fixed amplitude and starting time of each pulse. Modulating signal is a sinusoid with a 10 vpp and 10 khz. 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. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Amplitude demodulation matlab amdemod mathworks india. To study and perform pulse amplitude modulation and demodulation. Jan 30, 2014 modulation theory 4 a sine wave is represented as follows ct ac cos2. The carrier is a sinusoid with 1 vpp amplitude and 1 mhz.
The focus of this lab is to familiarize the student with the modulation and demodulation of an am signal. In this modulation, only half of the signal of the dsbsc is used. Amplitude modulation can be produced in various ways. University of north carolina at charlotte department of. To demodulate the modulated wave using envelope detector. Amplitude modulation is the changing the amplitude of the carrier signal with respect to the instantaneous change in message signal. Is there a way i can vary it, say, to 100% modulation depth. Yet, am continues to be used today in many communication applications. We will add additional functions to build the am demodulator. There are different types of modulation and so are demodulators.
In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. The second is to investigate classical analog amplitude modulation and the envelope detector. A modem is an equipment that performs both modulation and demodulation. Amplitude modulation of a sine or cosine carrier results in a variation of the carrier am plitude that is proportional to. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that. Analog modulation and demodulation amplitude modulation pages 306309. This can also be extended to frequency modulation fm and frequencyshift keying fsk, for these can be regarded as a special case of phase modulation.
Theory pulse width modulation is also referred as pulse duration modulation or less often pulse length modulation. Use your project files from the previous fir laboratory. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors.
Phase modulation analog pm and phaseshift keying digital psk can be regarded as a special case of qam, where the amplitude of the transmitted signal is a constant, but its phase varies. In the frequency domain, amplitude modulation corresponds to translating the baseband spectrum to a band. Amplitude modulation am is a modulation technique where the amplitude of a highfrequency sine. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier. Demodulation is the process by which the original information bearing signal, i. Amplitude modulation is one of the oldest forms of modulation. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Modulation d amplitude demodulation d amplitude pdf. This principle is at the heart of amplitude modulation.
Amplitude modulation am, demodulation and their circuit. Scribd is the worlds largest social reading and publishing site. Here well use the example of a square law fet as illustrated in figure 9. The operation theory of pcm modulation pcm modulation is a kind of source coding. Demonstrate understanding of frequency modulation and demodulation technique. The demodulation is performed by an envelope detector. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process.
We can define amplitude modulation by saying that a modulating signal, should produce an am wave of the form well use s instead of v or e to indicate that were talking about a modulated quantity and that it can be either a field or a voltage. In amplitude modulation theory, the amplitude of a carrier signal is varied by the modulating voltage, whose frequency is invariably lower than that of the carrier. This gives us something to modulate and carry the information pattern from. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Both processes aim to achieve transfer information with the minimum distortion, minimum loss and. In this experiment, you will examine the characteristics of amplitude modulation am. But the width of each pulse is made properly proportional to the amplitude of the signal at that instant. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection.
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