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. Amplitude modulation is defined as the process in which the amplitude of the carrier wave c t is varied about a mean value, linearly with the baseband signal. Without giving input measuref o free running frequency. To study sampling and reconstruction of pulse amplitude modulation system 6. With the oscilloscope observe the modulated waveform input to the. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. There are different types of modulation and so are demodulators. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. The demonstration centers around a number of signals displayed in both the time domain and the frequency domain using a signal generator, an oscilloscope to view the signal. The goal of this experiment is to become familiar with fm modulation and demodulation. When expressed as a percentage it is the same as the depth of modulation. Source called v1 generates the message to be transmitted. Demodulation is the process by which the original information bearing signal, i. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation.
Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and. Introduction for am signals, the information is carried by the amplitude or envelope of the signal. Build simple am modulator by using crystal oscillator.
Amplitude modulated signal can be represented by the following equation. Pdf simulation of analog modulation and demodulation. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. Demodulation the process of recovering or detecting the message signal from the modulated carrier frequency. To plot the wave form for binary amplitude shift keying bask signal using matlab for a stream of bits. Amplitude modulation am the process of combining the message signal with the carrier signal and the two sidebands. Yet, am continues to be used today in many communication applications. Techniques in virtual instrumentation and remote lab. Therefore, both fm and pm are often referred to as angle modulation.
Amplitude modulation an interactive demo which enables you to both see and hear the result of multiplying a sine wave with a cosine amplitude envelope. In this experiment, we shall consider demodulation using envelope detector. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. Adjust the carrier and modulated signals for a modulation index of 0. This lab introduces students to communications theory with amplitude modulation and demodulation.
The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. Fm modulation and demodulation electrical and computer. Amplitude modulation am, still widely used in commercial radio today, is one of the simplest ways that a message signal can modulate a sinusoidal carrier wave. Demodulation of am signal as stated earlier, an envelope detector has been used here for demodulation. Amplitude modulation early radio ee 442 spring semester. Then as the audio signal amplitude is changed to 150 mvpp, the percentage modulation dropped to around 30%. Bpsk modulation and demodulationreal time experiment. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Quadrature amplitude modulation qam pam signals occupy. In this experiment, you will examine the characteristics of amplitude modulation am. Build simple envelope detector for am demodulation. Apr 15, 2017 amplitude modulation and demodulation by.
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. All books are in clear copy here, and all files are secure so dont worry about it. The second is to investigate classical analog amplitude modulation and the envelope detector. Amplitude modulation am, demodulation and their circuit. Amplitude modulation am amplitude modulation is the process of varying the amplitude of a carrier wave in proportion to the amplitude of a baseband signal. It needs a carrier signal of higher frequency for long distance destination.
An interactive demo which enables you to both see and hear the result of multiplying a sine wave with a cosine amplitude envelope. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Department of electronics and communication engineering. Note that this is on the very low end of the recommended voltage range. Bikram modak departmentcomputer science and engineering semester4th roll no. Pdf amplitude modulation songkolon samanta academia. Connect frequency counter across the fm out sockets and measure free run span by rotating vr. Frequency division multiplexing, fdma amplitude modulation and demodulation.
That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. The demodulation of dsb am signal can be done either by using an envelope detector or by passing the amplitude modulated signal through a nonlinear device. This gives us something to modulate and carry the information pattern from. 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. As we mentioned before, well use dsbc modulation because of its ease in 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. Pdf experiment 1 amplitude shift keying using matlab.
This principle is at the heart of amplitude modulation. In modulation, one characteristic of a signal generally a sinusoidal wave known as the carrier is changed based on the information signal that we wish to transmit modulating signal. Here well use the example of a square law fet as illustrated in figure 9. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. Lecture 14, demonstration of amplitude modulation mit res. Experiment 1 design of conventional amplitude modulator. Lab 5 amplitude modulation and demodulation pages 1 7 text. Modulation allows us to transmit multiple signals in the same medium i. Phase modulation pm is a different form of frequency modulation and the carrier is similar in appearance to a frequencymodulated carrier. An am modulator is constructed usingthe analog devices ad534 four quadrant multiplier, and the properties of the resultingsignal are examined using labview. There are many ways to detect the envelope of am signals.
Amplitude shift keying ask is the digital modulation technique. An envelope detector figure 6a is an electronic circuit that takes a highfrequency modulated signal as input and provides an output which is the envelope of the original signal. Frequency modulation is a form of modulation, which represents information as variations in the instantaneous frequency of a carrier wave. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. To construct and study the amplitude modulation technique. Read online modulation d amplitude demodulation d amplitude book pdf free download link book now.
The message signal is, for example, a function of the sound to be reproduced by a. To study and perform phase shift keying 10 modulation and demodulation. Quadrature amplitude modulation is widely used for carrying many digital signals, everything from wifi to mobile phone communications and very much more. Amplitude modulation article about amplitude modulation by.
In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. To measure the percentage modulation, and the percentage of total power in both sidebands and in the carrier versus the modulation. Modulation damplitude demodulation damplitude pdf book. Amplitude modulation can be produced in various ways. In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal. You can publish your book online for free in a few minutes. Information signal is usually of low frequency, so it cannot travel far. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Lab 5 amplitude modulation and demodulation pages 1 7. To study and perform phase shift keying 10 modulation and. There are many methods of generating am, and this experiment explores only one of them. Introduction to analog communication modulation the process of combining the message signal with the car rier signal that causes the message signal to vary a characteristic of the carrier signal.
Overmodulated am signals and its requirement for coherent detection are also considered. If synchronous demodulation is used, the waveform is required at the demodulator. Phase modulation analog pm and phaseshift keying digital psk can be regarded as a special case of qam, where the amplitude of the transmitted signal is a constant, but its phase varies. Feel free to use either method to respond to the questions below. Oct 30, 2017 amplitude modulation and demodulation. The idea is simple, though the notion that it can be used to modulate. To generate amplitude modulation am waveform and to measure modulation index of am wave using waveform method. Connect frequency counter across the fm out sockets and measure free run span by rotating v r control to both.
In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. It is still in use today in a variety of systems, including, of course, am broadcast radio. To study frequency modulation and determine its modulation factor 4. Modulation is a process of translating information signal from low band frequency to high band frequency that is suits the transmission medium. An am wave may thus be dscribed, in the most general form, as a function of time. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. 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.
To study amplitude demodulation by linear diode detector 3. Indian institute of technology kanpur ee 381 electrical. Another method, which introduces more variables into the model, is explored in the experiment entitled. Demodulation is a key process in the reception of any amplitude modulated signals whether used for broadcast or two way radio communication systems. Then, students will use labview to program an am demodulator and use it to explore and visualize the. Download modulation d amplitude demodulation d amplitude book pdf free download link or read online here in pdf. Third, the am signal will be demodulated by an envelope detector and low pass filter com. Note down frequency and amplitude of the demodulated output waveform. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn. Carrier recovery scheme in the demodulator is shown in fig 2. This form of modulation is essentially derived from two carriers that are 90 out of phase and adding information, either analogue or digital.
Amplitude modulation the voltage dac vdac provides offset to the message signal mt. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Amplitude modulation am, still widely used in commercial radio today, is one of. Introduction modulation in the modulation process, some characteristic of a highfrequency carrier signal bandpass, is changed according to the instantaneous amplitude of. Feed the am wave to the demodulator circuit and observe the output 11. What is amplitude modulation, am electronics notes.
Each part may be of any convenient amplitude at the input to an adder. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Amplitude modulation is mostly used in the form of electronic communication. This can also be extended to frequency modulation fm and frequencyshift keying fsk, for these can be regarded as a special case of phase modulation. Hapter modulation and demodulation free online course. The frequency of the carrier remains constant frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a. Implementing an amplitude demodulator with a product detector. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. The demodulation is performed by an envelope detector. Now we will observe the demodulation of an am signal with the circuit shown in figure 87. For example, the wavelength of a 1 ghz electromagnetic wave in free space is 30. Laboratory manual principles of communication system lab ee226f ivth semester prepared by. Dec 08, 2016 the diode detector has been used for many years for detecting or demodulation signals using amplitude modulation, am.
Pdf an analog method to modulate and demodulate signals is presented in this short. Frequency modulation fm the process of combining the message. The gain of entire circuit is determined by the r8 value. Amplitude modulation definition, types, solved examples.
To study and perform pulse amplitude modulation and demodulation. The am diode detector offers simplicity and low cost. Experiment 10 amplitude modulation and demodulation introduction in this experiment we generate and display. Diode envelope detector amplitude modulation am demodulation. 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. In this experiment, the properties and characteristics of amplitude modulated amsignals and their frequency spectra are examined. Here is the circuit used for modulation and its simulation. The process of recovery of modulating signal is called demodulation. Provide the demodulator input with the am modulator constructed in this lab. To study and perform amplitude modulation and demodulation.
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