Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. The ideal modulated signal should have a minimum euclidean distance of 2. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. Publishers pdf, also known as version of record includes final page, issue and volume. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3.
In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Before we study in detail about pam lets know the concepts of modulation. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal. Although one of the earliest used forms of modulation it is still used today, mainly for long, medium and short wave broadcasting and for some aeronautical point to point. The transmitter circuit produces the am signal which is. The proposed link combines the pulse amplitude modulation pam technique with. Pulse amplitude modulation pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. The signal sent to line ismodulated in amplitude and hence the name pulse amplitude modulation pam. Responses to pulse trains with different pulse amplitudes, amplitude modulation frequencies, and modulation depths were modeled. Analog communication pulse modulation tutorialspoint. The emona datex addon board combines with the ni elvis platform, providing a foundation to assist the student in visualizing and better understanding the concepts. The purpose of this experiment is to introduce pulse code modulation pcm by approaching this technique from two fronts. The proposed data link in 7 is used to combine the pam.
Indian institute of technology kanpur ee 381 electrical. We also see how to use a balanced mixer to modulate a signal. An eye diagram for a pam4 signal is unusual, with three eye openings and four levels stacked vertically as shown in the figure. Commutator determines the synchronization and sequence of the channels signals to be sampled. The demod ulation is performed by an envelope detector. 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. But the width of each pulse is made properly proportional to the amplitude of the signal at that instant. Pulse amplitude modulation is used in sampling process. Demonstrate understanding of various amplitude modulation and demodulation. The amplitude modulation, am, modulation index can be defined as the measure of extent of amplitude variation about an unmodulated carrier. Information signal is usually of low frequency, so it cannot travel far.
Pulse amplitude modulation is the basic form of pulse modulation in which the signal is sampled at regular and each sample is made proportional to the amplitude of the modulating signal at the sampling instant. If the negative symbol is transmitted, the pdf for z will be as sketched below. The goal of this experiment is to become familiar with fm modulation and demodulation. Department of ece 11 ec207l analog communications lab ii iv b. Multiplexing is the process of combining signals from different information sourcesso that they can be transmitted over a common channel. The pulse may take any real voltage value that is proportional to the value of the original waveform. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. The simplest form of the pam modulator is an analog switch that is turned on and off at the rf carrier pulse rate. Farshad lahouti january 20, 2003 winter 2003 uw, ece 318 lecture notes 2 information source signal modulator propagation channel signal demodulator information destination analog communication system analog signals may be transmitted directly via carrier modulat ion over. In pulse amplitude modulation system the amplitude of a carrier pulse train is varied in accordance with the instantaneous level of the modulating signal. Connect this signal to the oscilloscope and the lowfrequency spectrum analyzer and check that you have the correct input. In the pulse amplitude modulation, the message signal is sampled at regular periodic or time intervals and this each. Am is defined as a process in which the amplitude of the carrier t i i d b t l li l ith b b d ct a cc cos 2.
Pdf timebased recovery technique for pulseposition and pulse. Pdf pulseposition and pulseamplitude modulation interface for. No information is lost, but the energy is redistributed in the frequency domain. User manual for pulse amplitude modulation and demodulation trainer. The simple pulse modulation technique called pulse amplitude modulation pam proved to be more power efficient than the pwm and consumes constant power for individual pulses like ppm. This is often denoted in percentage called as percentage modulation.
This complete 3volume lab manual offers handson labs for teaching basic analog and digital communication topics such as am, fm, snr concepts, sampling, tdm, and deltasigma modulation. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. Pulse amplitude modulation pam theory of and its applications. In this system we have a fixed amplitude and starting time of each pulse. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. Theory pulse width modulation is also referred as pulse duration modulation or less often pulse length modulation. It is a modulation system in which the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the signal at the instant of sampling. Modeling auditory processing of amplitude modulation ii. Eluru534007 department of electronics and communications digital communications lab manual ece 416 iv iv b. The pulse width modulation pwm varies the width of individual pulses according to the amplitude of. Tdm pulse amplitude modulationdemodulation trainer st2102. Experiment 1experiment 2 sampling and pulse modulation.
Explain generation and demodulation of pam, ppm and pwm with waveforms. Design and implementation of amplitude modulator and demodulator introduction communication is the most important needs from the very beginning of civilization. The influence of different parameters, such as adaptation and stochasticity, on longterm adaptation and modulation following behavior was investigated. Pulse amplitude modulation pam is the simplest pulse modulation scheme. The purpose of this lab is to explore digital communications with a software radio to understand how each component works together. To understand the operation theory of pcm demodulator. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. There are different kinds of modulation technique based on varying the properties of a pulse train. The implementation of the pcm demodulator is similar to experiment 3, which is ic. The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. Laboratory manual principles of communication system lab ee226f ivth semester prepared by. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. 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.
Pulseamplitude modulation, acronym pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. The standard form of an amplitude modulated am wave is defined by st a c 1 k a mt cos2f c t where k a is a constant called the amplitude sensitivity of the modulator. Hence, pam is continuous in amplitude but discrete in time. Telecommunications labs for emona datex addon board. Amplitude modulation am, demodulation and their circuit. For a perfect modulation, the value of modulation index should be 1, which means the modulation depth should be 100%. Pcm is a technique widely used in communication systems, in particular in the conversion of analog signals into their digital representation.
Each type of modulation is different and requires different techniques to recover demodulate the intelligence. Find out information about carrierless amplitudephase modulation. Let us combine the fourier transforms of the two functions. Explanation of carrierless amplitudephase modulation. 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. Pam can be timedivision multiplexed tdm, as can pulse code modulation pcm which is a digital signal. National college of science and technology amafel building, aguinaldo highway dasmarinas city, cavite experiment no. The focus of this lab is to familiarize the student with the modulation and demodulation of an am signal. Pcm will be explored in this experiment in three manners. There are many methods of generating am, and this experiment explores only one of them. Amplitude modulation am 9 t15 use speech or music from trunks as the message, and show that this also generates a trapezoid, and that setting the message amplitude so that the depth of modulation reaches unity on peaks a triangle is especially easy to do, using the gain control g of the adder. The width of the pulse varies in this method, but the amplitude of the signal remains.
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 with the amplitude of the audio signal. Overmodulated am signals and its requirement for coherent detection are also considered. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. The wave form of am modulation is shown in figure 3.
Explain generation and demodulation of pam, ppm and pwm. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. Cap was the first adsl design to be commercially deployed and, as of. To study and perform pulse width modulation and demodulation. Sampling theorem and pulse amplitude modulation pam. Analog communicationpulse amplitude modulation and demodulation trainer is proposed to user friendly to process the experiments and the trainer had all internal features like message signal, carrier signal, power supply etc. Chapter 3 amplitude modulation national sun yatsen university. To study sampling and reconstruction of pulse amplitude modulation system 6. Numerical model for smallsignal modulation response in verticalcavity surfaceemitting lasers michal wasiak,1, patrycja spiewak,1 nasibeh haghighi,2 marcin gebski,1,2 emilia pruszynskakarbownik, 1paulina komar, james a. Pam however is an amplitude modulated am form of a pulse carrier 2, and hence has all the advantages and disadvantages of the purely analog am, a major disadvantage being noise. When expressed as a percentage it is the same as the depth of modulation. To study and perform amplitude modulation 2 to study and perform frequency modulation and demodulation. Pulse amplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.
The first discovered a method for amplifying very weak signals and basically developed the amplitude modulation technique. Pdf on may 1, 2016, waleed madany and others published pulseposition and pulseamplitude modulation. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Amplitude modulation or am as it is often called, is a form of modulation used for radio transmissions for broadcasting and two way radio communication applications. In pam the amplitude of the individual pulses are varied according to the. Department of communication engineering digital communication systems lab cme 3lab.
In the positive half cycle of pam signal, diode conducts and current flows through r, whereas in negative half cycle, the diode is reversed biased and. In cochlear implant ci users with residual hearing, the electrodenerve interface can be investigated combining electricacoustic stimulation eas via electrocochleography ecochg, a technique. After converted to digital signal, it is easy for us to process the signal such as encoding, filtering the unwanted signal and so on. Its still used in radio systems to transmit audio signals although it has lesser in popularity compared to fm due to its lower signal to noise ratio. Department of electronics and communication engineering. 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. Note that this is on the very low end of the recommended voltage range. Pam the amplitude of the pulses is varied in step with the message signal. Analog communications lab manual s w iii ece i sem. Sideband pumpprobe technique resolves nonlinear modulation. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence.
To understand the operation theory of amplitude shift keying ask. Amplitude modulation early radio ee 442 spring semester. It needs a carrier signal of higher frequency for long distance destination. If the experiment is not completed in the stipulated time, the pending work has to be. Postlab questions must be answered in each experiment s. This experiment examines the characteristics of the amplitude modulation am process. The meaning of source coding is the conversion from analog signal to digital signal. In pulse amplitude modulation, the amplitude of regular interval of periodic pulses or electromagnetic pulses is varied in proposition to the sample of modulating signal or message signal. Amplitude modulation or am is a method to transmit signals via electromagnetic transmission. Additionally, software packages like national instruments lab view and. Analog communication lab manual, prepared by nakka. This lab gives you the opportunity to actually work on amplitude modulation and reinforce the theory taught in class. Pulse amplitude modulation is the basic form of pulse modulation.
Laboratory exercise on demodulation of pam signal asee peer logo. Pam4 indicates pulse amplitude modulation, with the 4 indicating four levels of pulse modulation. Amplitude modulation is defined as a process in which the amplitude of the carrier wave ct is varied linearly with the instantaneous amplitude of the message signal mt. Pulse amplitude modulation is the process by which the amplitude of the regularly spaced pulses varies according to the the amplitude of the modulating signal. Illustrate the concept of an amplitude modulated am waveform. Amplitude modulated signal can be represented by the following equation. Yet, am continues to be used today in many communication applications.
Principles of communication systems 20022003 8 chapter 7. At least 10 experiments are to performed by students in the semester. Another method, which introduces more variables into the model, is explored in the experiment entitled. For the lowfrequency signal generator, this is equivalent to setting channel a to a 2v amplitude with 30khz frequency, and setting channel b to am under destination and 50% modulation. Analog communication lab viva questions and answers pdf analog communication lab viva questions with answers pdf ac interview questions jntu free download. The lab will cover, analog to digital conversion, modulation, pulse shaping, and noise analysis 1. To study and perform pulse amplitude modulation and demodulation. The first transmission however, was performed by fessenden in 1906 from brant rock, massachusetts. Carrierless amplitudephase modulation article about. It is the extent of modulation denoted in percentage, and is denoted by m. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.
Pulse amplitude modulation pam is used extensively in telecommunications as an intermediate step of. In experiment 3, dsb signals were generated by the multiplication of a message signal with a carrier waveform. A two bit modulator pam4 will take two bits at a time and will map the signal amplitude to one of four possible levels, for example. However, the opening of each of these three eyes is a3. Quadrature amplitude modulation qam pam signals occupy. The demodulation is performed by an envelope detector. Experiment 3 amplitude modulation and envelope detection. A rectangular pulse of finite length t and finite amplitude a may be written as a ott rt. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process.
Why we use modulation to transmit the baseband signals. To provide a familiarization with the use of a multipliercircuit unit to generate an amplitudemodulated am signal, with an adjustable modulation factorm. Pcm is a digital scheme for transmitting analog data. Accepted manuscript numerical model for smallsignal. Amplitude modulation am is defined as a process in which the amplitude of the. Pulse position modulation ppm is an analog modulation scheme in which, the amplitude and the width of the pulses are kept constant, while the position of each pulse, with reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. Learn to observe the output of the agilent 33120a arbitrary waveform generator on the agilent 54645a oscilloscope 3.
Learn the concise history of amplitude modulation or am broadcasting technique. Amplitude growth of intracochlear electrocochleography in. Amplitude modulation part 1 in class you have studied the theory of amplitude modulation. Modulation is a process of translating information signal from low band frequency to high band frequency that is suits the transmission medium. A design of asymmetric digital subscriber line transceiver developed by bell labs.
In this circuit, we assume that the carrier applied to the diode is larger than the modulating. Experiment 5 frequency modulation 1 objective to understand the principles of frequency modulation and demodulation. Modeled auditory nerve responses to amplitude modulated. Pulse width modulation pwm or pulse duration modulation pdm or pulse time modulation ptm is an analog modulating scheme in which the duration or width or time of the pulse carrier varies proportional to the instantaneous amplitude of the message signal. What is amplitude modulation, am electronics notes. Denoting the modulating signal as mt, pulse amplitude modulation is achieved by multiplying the carrier with the mt. The output is a series of pulses, the amplitudes of which vary in proportion to the modulating signal. Suppose a train of rectangular pulses exists, of fixed width, and at the same pulse rate as a pam signal. The particular form of pulse amplitude modulation is referred to as natural pam, because the tops of the pulses follow the.
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