Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. This principle is at the heart of amplitude modulation. Amplitude modulation early radio ee 442 spring semester. 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. Pulse amplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Students will explore the mathematical theory behind amplitude modulation and use the analog discovery 2 to visualize the effects of amplitude modulation in the time and frequency domains.
In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Message power in st slide 6 powers in single tone case cont. In practice, the demodulation of suppressed carrier amplitude modulated signals requires fairly. Connections are made for the am modulator and demodulator as shown in the. 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. Hapter modulation and demodulation mit opencourseware. Pdf digital demodulator of the quadrature amplitude. Amplitude modulation can be produced in various ways. Introduction to modulation and demodulation modulation. Laboratory manual principles of communication system lab ee226f ivth semester.
Amplitude modulation am is a modulation technique used in electronic communication, most. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Envelope detector for demodulation of am signal pdf. 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. Bookmark file pdf amplitude modulation tutorial solutions. The demodulator is composed of a lowpass filter, whose cutoff frequency is slightly higher than fm. Amplitude modulation contents slide 1 amplitude modulation slide 2 the envelope and no overmodulation slide 3 example for single tone modulation slide 4 measuring the modulation index slide 5 transmitted vs. This site is like a library, use search box in the widget to get ebook that you want. The message signal is, for example, a function of the sound to be reproduced by a. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. 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. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation.
Modulation and demodulation using pll 51 10 mixer circuit using bjt 57 a quick reference. In frequency modulation, the amplitude of the carrier. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted. This gives us something to modulate and carry the information pattern from. Amplitude modulation is one of the oldest forms of modulation. Overmodulated am signals and its requirement for coherent detection are also considered. With no modulation, the am carrier is transmitted by itself. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The theory and equations show that furthest extent of the sidebands from the carrier corresponds to the highest frequency of the modulating tone for the amplitude modulated signal. Download as ppt, pdf, txt or read online from scribd. The idea is simple, though the notion that it can be used to modulate signals. Frequency modulation download ebook pdf, epub, tuebl, mobi. To study and perform frequency modulation and demodulation. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation.
Download modulation d amplitude demodulation d amplitude book pdf free download link or read online here in pdf. He also discovered the principle on which am is based, heterodyning, and. The demodulation is performed by an envelope detector. Amplitude modulation definition, types, solved examples. In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. To study and perform pulse amplitude modulation and demodulation. 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. Click download or read online button to get frequency modulation book now.
Introduction to modulation and demodulation free download as powerpoint presentation. Modulation is defined as the process by which some characteristics of a carrier signal is varied in accordance with a. Modulation damplitude demodulation damplitude pdf book. 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. What are the four principle operations involve in am reception. 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 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. Read online modulation d amplitude demodulation d amplitude book pdf free download link book now. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. The code for amplitude modulation am with control of modulation index ma has been developed using matlab according to conventional theory. Lab mannual for amplitude modulation and demodulation. The process of amplitude modulation consists of the amplitude of the carrier wave being varied in sympathy with a modulating signal.
Scribd is the worlds largest social reading and publishing site. All books are in clear copy here, and all files are secure so dont worry about it. These subsymbols are formed by grouping blocks of incoming bits in the constellation step. This lab introduces students to communications theory with amplitude modulation and demodulation. In this video, i have explained amplitude modulation by following outlines. Doublesideband suppressedcarrier transmission wikipedia. Envelope detection has numerous applications in the fields of signal processing and communications, one of which is amplitude modulation am detection or demodulation. 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. Amplitude modulation an overview sciencedirect topics. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is.
Analog modulation and demodulation amplitude modulation pages 306309. Then, students will use labview to program an am demodulator and use it to explore and visualize the. This type of modulation comes under digital modulation schemes. When the modulating information signal a sine wave is applied, the carrier amplitude. Amplitude modulation and frequency modulation these videos explain you what is modulation, different kinds of. Matlab code for amplitude modulation am file exchange. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal.
The demodulator is the circuit, or for a software defined radio, the software that is used to recover the information content from the overall incoming modulated signal. Doublesideband suppressedcarrier transmission dsbsc is transmission in which frequencies produced by amplitude modulation am are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio frequency carrier wave. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. Seeing a little of the theory and mathematics behind amplitude modulation gives a better understanding of how it works. 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. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example.
Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. 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. Both phase and frequency of carrier are known at the demodulator amplitude of carrier is not important since it in. Pulse amplitude demodulation peak detection is used to detect pam. When expressed as a percentage it is the same as the depth of modulation. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. In practice, the carrier may be highfrequency hf while the modulation is audio. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection.
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