In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique. Now, remember that if you are given a signal, you can measure the periods in the am signal and calculate those frequencies. In this case, since the source is a multimedia file rather than a pure sine wave, we need the dsp process, which is the resampling and filtering. Explain briefly in your report how amplitude modulation is accomplished by this circuit. Within the limits of the student edition of matlab, increase the number of datapoints to the maximum possible, and create a plot showing the harmonic distortion. The amplitude or the strength of a high frequency carrier wave is changed in accordance with the amplitude of message signal. This result is a coding the above formulas of am using matlab codes which is not.
What is modulation index modulation index in am and fm. Building simulink model of the music transmission using dsbam modulator and demodulator baseband here, we will implement the dsbam baseband modulator and demodulator using a music file as a source. To have example of fm modulation index, take sm5074 or sm5075, and apply external modulating signal say 1 khz with certain amplitude, the fm modulated signal when viewed in analog digital oscilloscope e. Typically the modulation depth is the amplitude modulation index expressed as a percentage. 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 modulation index should be a number between 0 and 1. Am is a method of transmitting signals, such as sound or digital information, in which the. Here is an example of using matlab simulink to demonstrate amplitude modulation. We have written the ngspice code for the modulator and.
If you are a newbie to simulink, please read our article introduction to simulink. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. It is strongly suggested that you examine your text book for other methods. Amplitude modulation matlab tutorial amplitude modulation in matlab with code.
There is another way of modulating a, sinusoidal carrier wave, namely, angle modulation in which the angle of the carrier wave is varied according to the baseband signal. You can use this element in the rfbudget object and the circuit object. A practical qpsk modulator implementation similar to the one shown in figure 9. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Sep 03, 2016 i want to do amplitude modulation of an audio signal. Jan 29, 2017 amplitude modulation am is a one of the conventional technique used to transmit message signals using a carrier wave. Amplitude modulation and frequency modulation duration. Am modulation using matlab code figure 1 depicts the audio signal, the carrier, and the amplitude modulated signal. Some of these sources can be included in the modulator model, and some are best captured in other models external to the modulator. Quadrature amplitude modulation of two sinusoidal signals. Its main advantage is that it is more resistant to additive noise than am. The modulation index is ratio of modulating signal voltagevm to the carrier voltagevc.
Lab 5 amplitude modulation and demodulation pages 1 7. If you are new to matlab, please go through our tutorials. Aly elosery october 25, 2010 this lab is divided into two parts. Matlab tutorial amplitude modulation how to generate amplitude modulation am using matlab. 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. Pdf teaching digital and analog modulation to undergradute. In this section we like to use matlab to generate an fm signal and model the frequency discriminator, similar to the circuit we completed in the lab. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%.
In reality the terms am modulation index and the am modulation depth are often used interchangeably, so there are often no hard and fast rules regarding their use. The ratio mpa defines the modulation index, which varies. The carrier frequency, fc, should be larger than the highest spectral component. Amplitude modulation am matlab tutorial behind the sciences. Chapter 8 frequency modulationfm fm was invented and commercialized after am.
Frequency modulation is widely used on frequencies above 30 mhz, and it is particularly well known for its use for vhf fm broadcasting. Amplitudemodulationanddemodulation electronics tutorial. Both the input and output signals are real scalar signals. If the input is u t as a function of time t, then the output is. Modulation for communications simulation matlab modulate. In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. Remember, for analysis purposes keep the modulation index and frequency the same as part 2, step 3. This way, the antenna size can be made small as well as more. Another method, which introduces more variables into the model, is explored in the experiment entitled. The output is a passband representation of the modulated signal. As an example, the following figure shows the amplitude modulation with mtsin2. Amplitude modulation in simulink am modulation matlab.
Amplitude modulation matlab tutorial amplitude modulation. In terms of modulation index mamac the equation of the modulated signal becomes. Oct 14, 20 amplitude modulation am is a one of the conventional modulation technique to transmit signals using a carrier wave. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Building simulink model of the music transmission using dsb am modulator and demodulator baseband here, we will implement the dsb am baseband modulator and demodulator using a music file as a source. When m is greater than 1, severe distortion results into the modulated waveform. Compare doublesideband and singlesideband amplitude modulation. The toolbox is welldocumented via the accompanying dstoolbox. We also provide online training, help in technical assignments and do freelance projects based on python, matlab, labview, embedded systems, linux, machine learning, data science etc. Am is a method of transmitting signals, such as sound or digital information, in which the amplitude. The deltasigma toolbox includes nearly 100 functions which support ntf synthesis, modulator simulation from an ntf or a structure, realization, dynamic range scaling, snr estimation and more. In this paper we introduce a tutorial on the use of the guide facility of matlab. Observe the matlab figures in both envelope detection techniques. Amplitude modulation am is a one of the conventional modulation technique to transmit signals using a carrier wave.
Sep 29, 2016 matlab tutorial amplitude modulation how to generate amplitude modulation am using matlab. The amplitude or strength of the high frequency carrier wave is modified in accordance with amplitude of the message signal. Use the spectrum analyzer to compare this modulator to the one in part 2. An am modulator is constructed using the analog devices ad534 four quadrant multiplier, and the properties of the resulting. In its various forms, iq modulation is an efficient way to transfer information, and it also works well with digital formats.
Modulate using doublesideband suppressedcarrier amplitude. This tutorial script summarizes the tasks and experiments done during the seminar. There are many methods of generating am, and this experiment explores only one of them. What is fm, frequency modulation electronics notes. In this experiment, the properties and characteristics of amplitude modulated am signals and their frequency spectra are examined. Jul 05, 2016 in this post we are going to apply what we learnt about the fm signals properties in our last post. Note that the gain is equivalent to the modulation index for this modulator. Amplitude modulation matlab tutorial amplitude modulation in matlab with code 2016 duration.
This video tutorial has been designed to suit the curriculum of cbse class 12 students. Open a new model window and create the model shown in figure 12 for an am modulator. How to simulate pam pulse amplitude modulation in matlab. The amplitude modulation and demodulation technique involved in this project comprises of three stages. Although it may not be quite as straightforward as amplitude modulation, nevertheless frequency modulation, fm, offers some distinct advantages. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Considering the difficulties faced by the designer in terms of hardware for designing such systems we have used a system that uses less hardware for this process. Introduction modulation is used in efficient radiation of signals. Practical circuitry is more likely to use a modulator, rather than the more idealised multiplier.
The product and adder blocks are found in the same sublibrary. We will do some exercises in matlab by using the functions fmmod and fmdemod. The dsbsc am modulator passband block modulates using doublesideband suppressedcarrier amplitude modulation. Simulink implementation of amplitude modulation technique. Am signal dft as you can see in the code, fs220500 hz, fc2000 hz and fm300 hz. Amplitude modulation definition, types, solved examples.
Jun 25, 2008 amplitude modulation matlab tutorial amplitude modulation in matlab with code 2016 duration. Instantaneous frequency the instantaneousfrequencyof cos. Amplitude modulation am matlab tutorial behind the. I searched the forums but couldnt find a problem similar to mine. Amplitude modulation is mostly used in the form of electronic communication. Build the simulink model of am modulator and demodulator figure7 explained in this manual. The following example illustrates the effect on the amplitudemodulated. As part of the modulation practices we simulated this am modulator circuit to test the effects of the modulation quotient in the signal we plan to transfer. The second and third are both a from of angle modulation, with second known as phase and third as frequency modulation.
Am modulation of audio file matlab answers matlab central. Oct 19, 2015 amplitude modulation and frequency modulation duration. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Abstractthis project explores the robust design of amplitude modulation and demodulation using bjt amplifier and diode detector. Nov 20, 20 amplitude modulation am is a one of the conventional technique used to transmit message signals using a carrier wave. Use the modulator object to create a modulator element. Let us understand modulation index in am amplitude modulation. Matlab code for amplitude modulation am file exchange. Lab 5 amplitude modulation and demodulation prelab 5. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that. This stores two files, one with the random bit sequence of nbit bits and the other file contains the active group being processed.
One modulation technique that lends itself well to digital processes is called iq modulation, where i is the inphase component of the waveform, and q represents the quadrature component. Am modulation, quadrature amplitude modulation qam, and frequency modulation. For the love of physics walter lewin may 16, 2011 duration. Amplitude modulation am is a one of the conventional technique used to transmit message signals using a carrier wave.
The modulation index is ratio of modulating signal voltage vm to the carrier voltage vc. Amplitude modulation matlab tutorial amplitude modulation in. In this video tutorial, we will provide a general introduction of terms of communication systems with emphasis on wireless transmission and reception. I want to do amplitude modulation of an audio signal. The code for amplitude modulation am with control of modulation index ma has been developed using matlab according to conventional theory. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In this post we are going to apply what we learnt about the fm signals properties in our last post.
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