Remember, for analysis purposes keep the modulation index and frequency the same as part 2, step 3. In this video tutorial, we will provide a general introduction of terms of communication systems with emphasis on wireless transmission and reception. Derive the fourier transform expression of the amplitude modulated signal dam w in the tutorial. Each part may be of any convenient amplitude at the input to an adder. Expand the expression and again all you need is table 4. Modulation index and percentage of modulationovermodulation and distortion the modulation index should be a number between 0 and 1. The amplitude or strength of the high frequency carrier wave is modified in accordance with amplitude of the message signal. Matlab code for amplitude modulation am file exchange. Here, the carrier signal is taken as a very high frequency signal.
This video presents amplitude modulation in both the time and frequency domains, showing what is happening at each step of the process. What is modulation index modulation index in am and fm. Simulink implementation of amplitude modulation technique. Another way to think is to realize that we are really plotting the amplitude. Changing the amplitude of the carrier am modulation is one type of modulation easy, cheap, lowquality used for am receiver and cbs citizen bands. The carrier signal and y have sampling frequency fs. Derive the fourier transform expression rljw of 4 in the tutorial. The modulation index should be a number between 0 and 1. As you can see, am signals are very easy to generate.
In this application note, we are going to show a convenient method. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In this modulation technique the frequency and the phase of the message signal remains constant and the value of amplitude gets modulated. Download pdf introduction in am schemes, the modulation index refers to the amplitude ratio of the modulating signal to the carrier signal. The general form of a sinusoidal signal can be written as ft. Amplitude modulation am is a one of the conventional technique used to transmit message signals using a carrier wave. Let us understand modulation index in am amplitude modulation. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value. Modulation is done at high power of carrier and modulating signal b. If you are a newbie to simulink, please read our article introduction to simulink. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. About amplitude modulation am the amplitude modulated wave is created by multiplying the amplitude of a sinusoid carrier with the message signal. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn.
Am modulation using matlab code figure 1 depicts the audio signal, the carrier, and the amplitude modulated signal. The carrier signal and x have a sampling frequency fs. The message signal is, for example, a function of the sound to be reproduced by a. A modulation index of 1 is the maximum level of modulation that can normally be applied and occurs when the envelope increases by a factor of 1, i. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Introduction modulation is used in efficient radiation of signals. Quadrature amplitude modulation qam pam signals occupy. Wire the output of the modulation index slider control into the other input of the multiply function. In a hybrid modulation with the following constellation pattern, the outlying signal sig2, has higher energy i. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Matlab tutorial amplitude modulation how to generate amplitude modulation am using matlab.
For a perfect or correct modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Phase modulation is another type of angle modulation very similar to frequency modulation. Frequency modulation is a type of angle modulation. Power amplifiers are required to boost the signal d. Amplitude modulation matlab tutorial amplitude modulation in.
The modulated signal y has zero initial phase and zero carrier amplitude, resulting from a suppressedcarrier modulation. Angle modulation changes the phase of a signal as well as its amplitude, where amplitude modulation leaves the phase unchanged. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. This video tutorial has been designed to suit the curriculum of cbse class 12 students. To understand amplitude and phase modulation, we change to the rotating frame of reference with. The code for frequency modulation fm with control of modulation index mf has been developed using matlab according to conventional theory. Generate pulse width modulation pwm waves for power converter control. To study and perform amplitude modulation 2 to study and perform frequency modulation and demodulation. 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. Amplitude modulation and demodulation abstracta 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 i. The modulated signal has zero initial phase and zero carrier amplitude, so the result is suppressedcarrier modulation. Measuring the modulation index of an am signal using an. With the help of fastfouriertransforms fft, the modulation index can be obtained by measuring the sideband amplitude and the carrier amplitude.
Pdf teaching mathematical intensive engineering based courses to. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Simulink implementation of amplitude modulation technique using. Multiple choice questions and answers on amplitude modulation. The amplitude modulation am modulation depth figure is complementary to the modulation index. Amplitude modulation am is an analog modulation scheme where the amplitude a of. Explain briefly in your report how amplitude modulation is accomplished by this circuit. The modulation index is ratio of modulating signal voltage vm to the carrier voltage vc. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Modulation index modulation index is defined as the ratio of peak of message signal to the peak of carrier signal.
Compare doublesideband and singlesideband amplitude modulation. Amplitude modulation matlab code file exchange matlab. In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. The carrier frequency, fc, should be larger than the highest spectral component. In amplitude modulation or am, the carrier signal has its amplitude. When m is greater than 1, severe distortion results into the modulated waveform. 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. Am is a method of transmitting signals, such as sound or digital information, in which the amplitude. Set g so that the sinewave peaks just fall to zero. The code for amplitude modulation am with control of modulation index ma has been developed using matlab according to conventional theory. Matlab code for frequency modulation fm file exchange.
The amount of modulation depends on the modulation index m and the carrier frequency fc. Amplitude modulation matlab ammod mathworks deutschland. Read the tutorial on amplitude modulation demodulation, 1. This tutorial explains how to create an amplitude modulation am signal in matlab. In our next post, we will see a frequency modulation fm tutorial in matlab. Amplitude modulation fundamentals unimap portal pages 1. In terms of modulation index mamac the equation of the modulated signal becomes.
Also in this paper we have implemented amplitude modulation technique with the help of matlab simulink. Use the spectrum analyzer to compare this modulator to the one in part 2. Modulation is done at lower power of carrier and modulating signal b. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Create a quadrature amplitude modulated signal from signals i and q using a. Pdf teaching digital and analog modulation to undergradute. Am modulation in order to transfer signals we need to transfer the frequency to higher level one approach is using modulation modulation. Amplitude modulation early radio ee 442 spring semester. Amplitude modulation am matlab tutorial behind the. 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 in analog communication tutorial 22. Modulation for communications simulation matlab modulate.
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