Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. Demonstrate understanding of various amplitude modulation and demodulation techniques. Lab 5 amplitude modulation and demodulation prelab 5. In amplitude modulation, the amplitude of the carrier wave is made to vary in accordance with the message signal. In amplitude modulation am, we utilize the amplitude of the audio signal to modulate the amplitude of carrier signal, which means that the amplitude of carrier signal will be varied. Before we study in detail about pam lets know the concepts of modulation. Analog communication lab manual, prepared by nakka. Remarks 1to perform amplitude shift keying ask modulation and demodulation. We can use this feature since it wont be a limit for us in this experiment. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. The demodulation is performed by an envelope detector.
The purpose of this lab is to explore digital communications with a software radio to understand how each component works together. This electrical signal is called the message or baseband signal. K is a constant called the amplitude sensitivity of the modulator. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power.
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. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Amplitude modulation and demodulation real time experiment. Read through the lab experiment to familiarize themselves with the components and assembly sequence. Department of electronics and communication engineering. The carrier and modulation inputs to the ad633 are multiplied to produce a double sideband signal.
Experiment 5 amplitude modulation preliminary discussion in an amplitude modulation am communications system, speech and music are converted into an electrical signal using a device such as a microphone. These different types of amplitude modulation schemes are used for different applications. An am modulator is constructed using the analog devices ad534 four quadrant multiplier, and the properties of the resulting. This is the audio frequency sine wave which will be our modulating signal whose frequency range is 300hz3. Introduction in this experiment you will model an am generator, making a signal of the type. In this experiment, a carrier signal and an audio modulating signal are applied to the modulator ic mc 1496 and the produced modulated waveform is observed. Pulse amplitude modulation is the basic form of pulse modulation. To generate amplitude modulated wave and determine the percentage modulation. The digital modulation experiments include pcm encoding and decoding. Along with circuit components, introductions, an appendix section which. In part i we generate the dsbsc signal using singletone. Build simple am modulator by using crystal oscillator.
Double sideband dsb and amplitude modulation am modules. Indian institute of technology kanpur ee 381 electrical. In amplitude modulation, the carrier frequency remains constant, but the instantaneous value of the. Yet, am continues to be used today in many communication applications. Note that this is on the very low end of the recommended voltage range. Generate and demodulate an amplitude shift keyed ask signal introduction amplitude shift keying ask is a form of amplitude modulation that represents digital data as. The second is to investigate classical analog amplitude modulation and the envelope detector.
For example, conventional double sideband am is used in radio broadcast, single sideband suppressed carrier am is used in analog telephony and vestigial sideband am is used in tv broadcast. To demodulate the modulated wave using envelope detector. To observe the time domain waveforms and frequency spectra of amplitude modulated am waveforms both before and after demodulation and to design an experiment utilizing an fm signal. Ens 203 amplitude modulation and demodulation lab 6 radio. The message signal is, for example, a function of the sound to be reproduced by a. Audio oscillator, wideband true rms meter, multiplier, adder, utilities, phase shifter, tuneable lpf, quadrature utilities, noise generator, speech, headphones 0 pre laboratory reading double sideband dsb is one of the easiest modulation techniques to understand, so it is a good. Each experiment, whenever applicable, contains the following sections. Frequency of the input carrier is fixed at constant amplitude of 1. In this video i tried to explain the experiment amplitude modulation and demodulation. Eee3208 communication theory lab ahsanullah university. Demonstrate understanding of frequency modulation and demodulation technique. Overmodulated am signals and its requirement for coherent detection are also considered. Amplitude modulation is one of the earliest radio modulation techniques.
To study and perform amplitude modulation and demodulation. This experiment examines the characteristics of the amplitude modulation am process. Parti experiment4doublesidebandsuppressed carrier dsbsc. Amplitude modulation am the process of combining the message. In this experiment, the properties and characteristics of amplitude modulated am signals and their frequency spectra are examined. Experiment 5 amplitude modulation national instruments. This lab gives you the opportunity to actually work on amplitude modulation and reinforce the theory taught in class. In this experiment we shall consider double sideband am. Amplitude modulator circuit with ad633 the ad633 can be used as a linear amplitude modulator with no external components. Now, change the sinusoid message signal to square wave signal. The digital modulation experiments include pcm encoding and decoding, line codes and digital carrier modulation ask and fsk. By the end of this experiment, the student should be able to. Another method, which introduces more variables into the model, is explored in the experiment entitled.
We also see how to use a balanced mixer to modulate a signal. This is a laboratory manual for analog communication experiments. The message signal is then used to electrically vary the amplitude. For am experiment, connect the output of the throttle block to a. There are many methods of generating am, and this experiment explores only one of them. Amplitude modulation a1 49 you will see in this experiment, and in others to follow, that there is no problem in generating an am signal with a depth of modulation exceeding 100%, and without. Its simplest form is accomplished by the multiplication between a bandlimited message signal and a cosine called carrier, whose frequency is. Therefore, both fm and pm are often referred to as angle modulation.
Connections are made for the am modulator and demodulator as shown in the circuit diagrams. The demodulation circuit is used to recover the message signal from the incoming am wave at the. Experiment 2 experiment 6 experiment dsb sc modulation. To examine the effect of noise and attenuation on ask systems. In amplitude modulation the amplitude of high frequency sine wave carrier is. Amplitude modulation simulation experiment introduction. Amplitude modulation am is defined as a process in which the amplitude of the. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process.
Amplitude shift keying theory with lab experiment duration. I tried to explain the circuit connections that is needed for the experiment. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Cme3lab manual amplitudeshift keying ask experiment 6.
The purpose of this lab is for you to gain familiarity with the concepts of amplitude. What effect did the variation of the modulating signal amplitude have on the modulation index in the circuit of figure 85. Department of ece 11 ec207l analog communications lab ii iv b. The lab will cover, analog to digital conversion, modulation, pulse shaping, and noise analysis 1. For the circuit in figure 87, how did the time constant of the rc network compare with the. Repeat the experiment for different input signal and sampling frequencies. Ee 392 electrical engineering laboratory iii amplitude and frequency modulation objectives. Build simple envelope detector for am demodulation. The receivers used to listen to amdsbc are perhaps the simplest receivers of any radio modulation technique. In this experiment, you will examine the characteristics of amplitude modulation am.
Post lab questions must be answered in each experiment s laboratory report. Am modulation, quadrature amplitude modulation qam, and frequency modulation. Lab assignment 2 amplitude modulation 1 introduction this lab assignment is concerned with practical issues associated with the implementation of modulators and demodulators for doublesideband suppressed carrier dsbsc and doublesideband large carrier dsblc modulation. Amplitude modulation part 1 in class you have studied the theory of amplitude modulation. To achieve ssb amplitude modulation, we will utilize the following three blocks on the module. Analog communications lab manual pdf ac lab manual pdf.
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