Oct 30, 2017 amplitude modulation and demodulation. This conforms to the expectation as the maximum and minimum peak of the modulated signal waveform varies proportional to the amplitude of the modulating signal. Matlab script simulating the modulating and demodulation. Content introduction what is modulation types of modulation amplitude modulation modulation index amplitude demodulation circuit diagram about project conclusion 3. Modulation is the process of altering the characteristics of the amplitude, frequency, or phase angle of the highfrequency signal in accordance with the instantaneous value of the modulating wave. Set g so that the sinewave peaks just fall to zero. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Am modulation and demodulation with circuit and output 1. Because of amplitude modulation wavelength, am signals can propagate longer distances.
Amplitude modulationwhich of course is the origin of the term am radiovaries the amplitude of the carrier according to the instantaneous value of the baseband signal. If not, what is the default depth of modulation for am here. Frequency division multiplexing, fdma amplitude modulation and demodulation. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. The modulated signal y has zero initial phase and zero carrier amplitude, resulting from a. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier. There are different types of modulation and so are demodulators. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. The carrier signal and y have sampling frequency fs. This block diagram consists of the differentiator and the envelope detector. Message signal embed into the amplitude of carrier simple am is also called. Communications i amplitude modulations and demodulations. Modulation allows us to transmit multiple signals in the same medium i.
Am modulation and demodulation cypress semiconductor. Nestor project nevod nims nina accelerator nistf1 nmssm nnpdf. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. From the diagram, it can be seen that the envelope of the signal follows the contours of the modulating signal. May, 2016 am modulation and demodulation with circuit and output 1. Pulse position modulation ppm is an analog modulation scheme in which, the amplitude and the width of the pulses are kept constant, while the position of each pulse, with reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. Amplitude modulation and demodulation of harmonic signal. Actually, am modulation creates two copies of the original signal, one at 20003000hz band and another at 30004000hz.
Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2. Then, students will use labview to program an am demodulator and use it to explore and visualize the. Then, students will use labview to program an am demodulator and use it to explore and visualize the effects. What is amplitude modulation, am electronics notes. The am generator, or exciter, as such a low power source of modulated signal is often called, is now set up. Amplitude modulation and demodulation university of st andrews. Adaptation of the information signal to the transmission channel. Frequency and phase modulation are actually quite similar and are classified under the category of angle modulation. Ammeter ampere amplifier amplitude distortion amplitude modulation. Analog communication fm demodulators tutorialspoint.
Indian institute of technology kanpur ee 381 electrical. Process by which a property or a parameter of a signal is varied in proportion to a second signal. Amplitude modulation and demodulation abstract a single tone sinusoidal signal is transmitted using amplitude modulation and is demodulated at the receivers end using an envelope detector and the attenuated signal is amplified using common source bjt amplifer. The concepts of amplitude modulation, modulation and demodulation, along with their differences is explained below. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. This means, it converts the frequency variations of fm wave into the corresponding voltage amplitude variations of am wave.
Apr 15, 2017 amplitude modulation and demodulation by. The mathematical relationship for amplitude modulation is simple and intuitive. Am modulation and demodulation with circuit and output. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value.
Discover the key aspects about the demodulation detection of amplitude modulated signals. Signal waveform of amplitude modulation let the amplitude of the audio signal be mt a m cos. Hi, im a beginner in matlab and im just wondering whether the modulation constant. 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. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Aly elosery october 25, 2010 this lab is divided into two parts. Since amplitude modulation signal utilizes audio signal to modulate carrier signal, which means the variation of carrier signal amplitude is followed by the change of audio signal amplitude. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. Amplitude modulation am, demodulation and their circuit. 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. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Yet, am continues to be used today in many communication applications. Demodulation is a key process in the reception of any amplitude modulated signals whether used for broadcast or two way radio communication systems. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation.
Bikram modak departmentcomputer science and engineering semester4th roll no. Demodulation is the process by which the original information bearing signal, i. Each channel sharing scheme a set of basis vectors. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. From modulation the signal carrier we are provided with amplitude modulation am, frequency modulation fm, or phase modulation pm. Introduction modulation in the modulation process, some characteristic of a highfrequency carrier signal bandpass, is changed according to the instantaneous amplitude of. Amplitude modulation am works by varying the amplitude strength of a carrier signal, in proportion to amplitude of a modulation signal that is to be transmitted to one or more receivers. In part i you will learn how to design an amplitude modulator am and in part ii you will be able to demodulate an am signal. For amplitude modulation, we use simple and low cost circuit. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. To study and perform phase shift keying 10 modulation and.
This process of imposing an input signal on a carrier wave is known as modulation. This type of modulation is used to transmit analog as well as digital baseband signals. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Design and implementation of amplitude modulator and demodulator introduction communication is the most important needs from the very beginning of civilization. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. 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. 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. 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. Modulation makes my voice to exchange band from 0 to 20004000hz.
When the modulation source is an audiofrequency oscillator and the destination is the gain of a vca in the audio signal path, we call the result amplitude modulation, or am for short. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast. Analog communication pulse modulation tutorialspoint. 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. The depth of modulation, defined below, can be adjusted with the adder gain control g. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast a modulator is a device that performs modulation.
To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. To be exact, this modulation is named amsc supressed carrier, for a reason that i will clarify a bit later. In the process of amplitude modulation, the frequency and phase of the carrier remain constant whereas the maximum amplitude varies according to the instantaneous value of the information signal. Linear amplitude modulation applications technical articles. Hence the objective of amplitude demodulator is to take out the variation envelop detection from modulated. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Differentiator is used to convert the fm wave into a combination of am wave and fm wave. As we mentioned before, well use dsbc modulation because of its ease in demodulation. We will now demodulate the double side band amplitude modulated signal from part 1b above. Here is the circuit used for modulation and its simulation.
The resulting signal from the process of amplitudemodulation is called amplitude modulation signal of simply am wave. Is there a way i can vary it, say, to 100% modulation depth. This principle is at the heart of amplitude modulation. Amplitude modulation article about amplitude modulation. The original amplitude modulation is a family of modulation schemes, in which the amplitude of a. This signal should have a carrier frequency of 20 khz and be 100 percent modulated in the frequency range from 200 to hz. At the receiving station, the message signal is extracted from the modulated carrier by demodulation. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam. Double sideband large carrier dsblc modultion for general message signal mt. An interactive demo which enables you to both see and hear the result of multiplying a sine wave with a cosine amplitude envelope. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. Then as the audio signal amplitude is changed to 150 mvpp, the percentage modulation dropped to around 30%. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave.
Hapter modulation and demodulation mit opencourseware. Amplitude modulated signal can be represented by the following equation. Analog modulation and demodulation amplitude modulation pages 306309. Amplitude modulation am is defined as modifying the amplitude of the carrier wave according to the message or information signal. I find am a fascinating topic, not least because it has a quite unexpected result. Fields or signals modulated in these ways are for obvious reasons called am amplitude modulated, fm frequency modulated, or pm phase. Amplitude modulationdemodulation in matlab file exchange. Source called v1 generates the message to be transmitted. The idea is simple, though the notion that it can be used to modulate signals. Amplitude demodulation matlab amdemod mathworks united.
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