Seeing a little of the theory and mathematics behind amplitude modulation gives a better understanding of how it works. Scribd is the worlds largest social reading and publishing site. When the modulating information signal a sine wave is applied, the carrier amplitude. 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. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. 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. 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. Message power in st slide 6 powers in single tone case cont. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Amplitude modulation am is a modulation technique used in electronic communication, most.
The modulated carrier signal is sent to the receiver where demodulation of the carrier occurs to. Each channel sharing scheme a set of basis vectors. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Both phase and frequency of carrier are known at the demodulator amplitude of carrier is not important since it in. In this video, i have explained amplitude modulation by following outlines. 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. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. Modulation is defined as the process by which some characteristics of a carrier signal is varied in accordance with a. This site is like a library, use search box in the widget to get ebook that you want. Download modulation d amplitude demodulation d amplitude book pdf free download link or read online here in pdf.
Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. Pulse amplitude demodulation peak detection is used to detect pam. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. 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. 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. 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. Envelope detection has numerous applications in the fields of signal processing and communications, one of which is amplitude modulation am detection or demodulation. Figure 7 labview vis that you need to complete the am modulation and demodulation block diagram below figure 8 completed am modulation and.
Here well use the example of a square law fet as illustrated in figure 9. 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. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Read online modulation d amplitude demodulation d amplitude book pdf free download link book now. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Amplitude modulation is one of the oldest forms of modulation. With no modulation, the am carrier is transmitted by itself. When expressed as a percentage it is the same as the depth of modulation. Introduction to modulation and demodulation modulation. Click download or read online button to get frequency modulation book now. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process.
In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. 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. This lab introduces students to communications theory with amplitude modulation and demodulation. In practice, the carrier may be highfrequency hf while the modulation is audio. Amplitude modulation early radio ee 442 spring semester. Bookmark file pdf amplitude modulation tutorial solutions. 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. Amplitude modulation an overview sciencedirect topics. The message signal is, for example, a function of the sound to be reproduced by a. Then, students will use labview to program an am demodulator and use it to explore and visualize the. Modulation and demodulation using pll 51 10 mixer circuit using bjt 57 a quick reference. Analog modulation and demodulation amplitude modulation pages 306309.
The code for amplitude modulation am with control of modulation index ma has been developed using matlab according to conventional theory. What are the four principle operations involve in am reception. The process of amplitude modulation consists of the amplitude of the carrier wave being varied in sympathy with a modulating signal. Amplitude modulation can be produced in various ways. Envelope detector for demodulation of am signal pdf.
These subsymbols are formed by grouping blocks of incoming bits in the constellation step. In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. Pdf digital demodulator of the quadrature amplitude. In frequency modulation, the amplitude of the carrier.
This type of modulation comes under digital modulation schemes. Introduction to modulation and demodulation free download as powerpoint presentation. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. To study and perform frequency modulation and demodulation. Lab mannual for amplitude modulation and demodulation. Amplitude modulation and frequency modulation these videos explain you what is modulation, different kinds of. Amplitude modulation definition, types, solved examples. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. Hapter modulation and demodulation mit opencourseware. This principle is at the heart of amplitude modulation. 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. Matlab code for amplitude modulation am file exchange.
Download as ppt, pdf, txt or read online from scribd. Amplitude modulation theory frequency spectrum power. Frequency modulation download ebook pdf, epub, tuebl, mobi. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. The idea is simple, though the notion that it can be used to modulate signals. 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. 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. To study and perform pulse amplitude modulation and demodulation. 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.
The demodulation is performed by an envelope detector. Keying is indicating the transmission of digital signal over the channel. To study and perform amplitude modulation and demodulation. Restoring or recovering the message signal from the received. 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. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio frequency carrier wave. Connections are made for the am modulator and demodulator as shown in the. 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. The demodulator is composed of a lowpass filter, whose cutoff frequency is slightly higher than fm. He also discovered the principle on which am is based, heterodyning, and.
In practice, the demodulation of suppressed carrier amplitude modulated signals requires fairly. Modulation damplitude demodulation damplitude pdf book. On its basis there can be realized the algorithms and the correspondent digital devices for detection and noncoherent demodulation of signals with amplitude, frequency modulation and differential. 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. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Doublesideband suppressedcarrier transmission wikipedia.
Laboratory manual principles of communication system lab ee226f ivth semester. 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. This gives us something to modulate and carry the information pattern from. All books are in clear copy here, and all files are secure so dont worry about it. 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. Overmodulated am signals and its requirement for coherent detection are also considered.
863 280 864 1483 273 1266 1523 324 227 174 766 1216 1482 47 693 459 264 895 197 1476 1347 280 876 1298 218 185 1101 1507 1086 294 691 975 296 1335 714 912 1205 1128 1340 733 170 834 461