Introduction modulation is used in efficient radiation of signals. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. The message signal is, for example, a function of the sound to be. Aly elosery october 25, 2010 this lab is divided into two parts. Group3 umang gupta 2010ee50564 indrabhushan 2010ee50548 vivekmangal 2010ee50566 jitendra kumar meena 2009ee50483 12912 experiment 2. The original waveform amplitude is quantized with a resulting loss of information. Types of modulation sine wave carrier described by 3 parameters. Explain briefly in your report how amplitude modulation is accomplished by this circuit. Also in this paper we have implemented amplitude modulation technique with the help of matlab simulink. The carrier signal and y have sampling frequency fs. Compare doublesideband and singlesideband amplitude modulation.
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. So can have amplitude modulation am frequency modulation fm phase modulation pm frequency and phase combined are known as angle modulation 8. Frequency modulation an overview sciencedirect topics. The mfile will show these values in the matlab command window. Amplitude modulation is mostly used in the form of electronic communication. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. The amplitude of the modulation signal determines the amount of the frequency change from the center frequency. 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 analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal. Lab 5 amplitude modulation and demodulation prelab 5. Lab 5 amplitude modulation and demodulation pages 1 7.
The modulated signal has zero initial phase and zero carrier amplitude, so the result is suppressedcarrier modulation. If you are new to matlab, please go through our tutorials. Is there a way i can vary it, say, to 100% modulation depth. Amplitude modulation lab report and grading format 1 report format 1. Matlab code print the code for the following question with the report and also submit the. The amplitude or strength of the high frequency carrier wave is modified in accordance with amplitude of the message signal. The amplitude of the fm signal is constant at all times and is independent of the modulation signal.
In your report compare the different modulation schemes. The modulated signal y has zero initial phase and zero carrier amplitude, resulting from a suppressedcarrier modulation. If not, what is the default depth of modulation for am here. Here is the circuit used for modulation and its simulation. If this minimum value is zero, the modulation depth is 100%. Amplitude modulation matlab ammod mathworks france. Hi, im a beginner in matlab and im just wondering whether the modulation constant. Amplitude modulation am, demodulation and their circuit. Amplitude modulation using matlab free download as powerpoint presentation.
It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. The carrier frequency, fc, should be larger than the highest spectral component. Matlab mfiles for the prelab are available on the commlab web site, located at. Amplitude modulation definition, types, solved examples. Using matlab and the frequency and time domain representations derived above, plot the time and frequency representations of dsblc signals with a c 1v and modulation indices of 25%, 66. Note that this is on the very low end of the recommended voltage range. 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. Intro to generation of ask amplitude shift keying ask in the context of digital communications is a modulation process, which imparts to a sinusoid two or more discrete amplitude levels. Amplitude modulation in simulink am modulation matlab.
Frequency division multiplexing, fdma amplitude modulation and demodulation. Amplitudefrequency modulation communication system. Amplitude modulation using matlab modulation amplitude. 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 am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Am amplitude modulation, m modulation index, fccarrier frequency, fmmodulating frequency. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal.
Frequency modulation fm is the modulation technique that represents information as variations in the frequency of the carrier wave, whereas in am, the carrier amplitude is varied while its frequency remains constant. In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of the data signal, as shown in figure 2. Then as the audio signal amplitude is changed to 150 mvpp, the percentage modulation dropped to around 30%. Use the spectrum analyzer to compare this modulator to the one in part 2. The amplitude or the strength of a high frequency carrier wave is changed in accordance with the amplitude of message signal. This way, the antenna size can be made small as well as more. An am modulator is constructed usingthe analog devices ad534 four quadrant multiplier, and the properties of the resultingsignal are examined using labview. Modulation allows us to transmit multiple signals in the same medium i.
An am wave may thus be dscribed, in the most general form, as a function of time as follows. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. The purpose of this lab is for you to gain familiarity with the concepts of amplitude. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Remember, for analysis purposes keep the modulation index and frequency the same as part 2, step 3.
Frequency modulation is a form of modulation, which represents information as variations in the instantaneous frequency of a carrier wave. In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. To generate and demodulate an amplitude shift keyed ask signal and a binary fsk signal. The frequency of the modulation signal determines the rate of the frequency change from the center frequency. 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. As we mentioned before, well use dsbc modulation because of its ease in demodulation. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. Matlab code for amplitude modulation am file exchange. No information is lost, but the energy is redistributed in the frequency domain. Communication systemsamplitude modulation wikibooks.
The receivers used to listen to amdsbc are perhaps the simplest receivers of any radio modulation technique. Here is an example of using matlab simulink to demonstrate amplitude modulation. Amplitude modulation matlab ammod mathworks deutschland. The pulse may take any real voltage value that is proportional to the value of the original waveform. Source called v1 generates the message to be transmitted. Choose the other parameters so that you can easily compare these results with those that you measure in the lab. In this experiment, the properties and characteristics of amplitude modulated amsignals and their frequency spectra are examined. Amplitude modulation am is a one of the conventional technique used to transmit message signals using a carrier wave. Show the resultsplots, you can use excel or a snap shot or draw it by hand. This video uses properties of the fourier transform to explain modulation and demodulation inside a simple am radio system.