To study and perform frequency modulation and demodulation. There are many types of modulation so there are many types of demodulators. Quadrature amplitude modulation qam requires changing the phase and amplitude of a carrier sine wave. In this system we have a fixed amplitude and starting time of each pulse. Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. Recall that our goal is to transmit data over a commu nication link, which we achieve by mapping the. The amplitude of the high frequency carrier of the signal is.
Of course, you cannot apply ordinary amplitude demodulation to a frequencymodulated signal. All books are in clear copy here, and all files are secure so dont worry about it. This gives us something to modulate and carry the information pattern from place to place. This chapter describes the essential principles behind modulation and demodulation, which we introduced briefly in chapter. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. Amplitude modulation am is an analog modulation scheme where the amplitude a of. 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. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Hapter modulation and demodulation mit opencourseware. Amplitude modulationdemodulation in matlab file exchange. Learn about the most straightforward way of encoding information in a carrier waveform. University of north carolina at charlotte department of. Sinusoidal amplitude modulation amplitude demodulation.
Amplitude modulation and demodulation 1 lab notes a word about power. Modulation and demodulation pdf on the various aspects of modulation and demodulation. Amplitude modulation is defined as a process in which the amplitude of the carrier wave ct is varied linearly. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. Understanding quadrature demodulation radio frequency. Aug 19, 2006 hey all, i am having some trouble with am demodulation using matlab. For the second simulate signal vi, wire the output of the modulation frequency slider control into the frequency input.
Frequency shift keying demodulation matlab fskdemod. Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Brand, philips semiconductors, pcale qam demodulation 1 wireless communications example application area multiplexing compression settop box radio compression bit rate reduction multiplexing assembly of multiple programs modulation conversion to transmission format settop box integrated receiver decoder ird. This modification is performed according to a specific scheme that is.
What we do in am, very roughly,is to throw away the frequency content of. The term demodulator is used because the demodulation process is considered to be the opposite of modulation. To study and perform amplitude modulation and demodulation. In this video, i have explained amplitude modulation by following outlines. The modulator the modulator outputs two files, the first with the modulated signal exactly n real elements long and the. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. In electronics and telecommunications, modulation is the process of varying one or more. Modulation demodulation software radio how to build and setup the mdsr software v2.
Wire a constant value of 1 into the amplitude input by rightclicking on the connector and selecting createconstant. Explain generation and demodulation of pam, ppm and pwm. Why frequency modulation is better than amplitude modulation. The rate at which the amplitude of the carrier is changed is called the modulation rate.
In frequency modulation, the amplitude of the carrier. The carrier signal and y have sample frequency fs hz. Amplitude modulation can be produced in various ways. Amplitude modulation am is a modulation technique where the. I used the builtin matlab function butter to design a low pass filter and using the transfer function obtained, i filtered the modulated signal multiplied by the carrier. Aly elosery october 25, 2010 this lab is divided into two parts.
Doublesideband suppressedcarrier transmission dsbsc is transmission in which frequencies produced by amplitude modulation am are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level. 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. This lab introduces students to communications theory with amplitude modulation and demodulation. Radio modulation modes telecommunication theory television terminology. The audio waveform modifies the amplitude of the carrier wave and determines the envelope of the waveform. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise.
For the sake of simplicity, ka 1 and ar ac have been chosen lowpass. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. I ntroduction an amplitude modulated signal is composed of both low frequency and high frequency components. The radio wave was called a carrier, since it was seen to carry the speech information with it. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. Fsk modulationdemodulation ni community national instruments.
This chapter describes the essential principles behind. Theory shows that in order to transmit a wave effectively, the length of the. Yet, am continues to be used today in many communication applications. Amplitude into amplitude input and carrier frequency into frequency input. Each channel sharing scheme a set of basis vectors. Hi, im a beginner in matlab and im just wondering whether the modulation constant. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted.
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. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. Here well use the example of a square law fet as illustrated in figure 9. Modulation damplitude demodulation damplitude pdf book. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. The circuit in which restoration is achieved is called the detector. As such the diode detector or demodulator is able to provide an output proportional to the amplitude of the envelope of the amplitude modulated signal. We will add additional functions to build the am demodulator. We have seen that rf modulation is simply the intentional modification of the amplitude, frequency, or phase of a sinusoidal carrier signal. 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 contents slide 1 doublesideband suppressedcarrier amplitude modulation slide 2 spectrum of a dsbscam signal slide 3 why called doublesideband slide 4 ideal coherent receiver slide 5 coherent receiver analysis slide 6 spectra in dsbscam system slide 7 demodulator using the preenvelope slide 8 costas loop demodulator. Double sideband suppressed carrier dsb sc modulation. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.
The am diode detector is an envelope detector it provides an output of the envelope of the signal. This is the mdl file which demonstrate the bpsk modulation and demodulation using carrier recovery, carrier frequency is used at 4khz and data rate 1k. One of the easiest ways to implement qam with hardware is to generate and mix two sine waves that are 90 degrees out of phase with one another. Download modulation d amplitude demodulation d amplitude book pdf free download link or read online here in pdf. 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. The spectral efficiency of the transmitted ask waveform is also a consideration and the m. Each part may be of any convenient amplitude at the input to an adder. In the frequency domain, amplitude modulation produces a signal with power concentrated at the carrier frequency and two adjacent sidebands. Theory pulse width modulation is also referred as pulse duration modulation or less often pulse length modulation. First, students will generate an am signal using data from a file, and then they will use the envelope detector method to recover the original message by connecting the am signal to a rectifier and the. Doublesideband suppressedcarrier transmission wikipedia. Analog modulation and demodulation amplitude modulation pages 306309. A modem is an equipment that performs both modulation and demodulation.
What links here related changes upload file special pages permanent link page information. The purpose of this lab is for you to gain familiarity with the concepts of amplitude. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. Frequency modulation and phase modulation are the two complementary principal methods of angle modulation. Amplitude modulation contents slide 1 amplitude modulation slide 2 the envelope and no overmodulation slide 3 example for single tone modulation slide 4 measuring the modulation index slide 5 transmitted vs. Npsk modulation and demodulation the demonstration of npsk modulation and demodulation with my own speech, with different value of n and sampling frequency and carrier, n 2, 4, 8. In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. Quadrature amplitude modulation qam national instruments.
Message power in st slide 6 powers in single tone case cont. The modulated signal y has zero initial phase and zero carrier amplitude, so it represents suppressed carrier modulation. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Amplitude demodulation matlab amdemod mathworks india. Explain generation and demodulation of pam, ppm and pwm with waveforms. In this video i tried to explain the experiment amplitude modulation and demodulation. 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. Note that this is on the very low end of the recommended voltage range. Sinusoidal amplitude modulation amplitude demodulation synchronous and asynchronous double and singlesideband am modulation pulseamplitude modulation pulse code modulation frequencydivision multiplexing timedivision multiplexing narrowband frequency modulation. A demodulator is an electronic circuit or computer program in a softwaredefined radio that is used to recover the information content from the modulated carrier wave.
Amplitude modulation is one of the oldest forms of modulation in analog communication. Use your project files from the previous fir laboratory. If the received carrier phase is assumed to be constant, each of the seven reference values will have to be shifted only once at the beginning of the simulation. The code for amplitude modulation am with control of modulation index ma has been developed using matlab according to conventional theory. In experiment 3, dsb signals were generated by the multiplication of a message signal with a carrier waveform. In theory the total integrated noise approaches zero as the filter bandwidth goes to zero. 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. To study and perform pulse amplitude modulation and demodulation. Eventually i would like to send the modulated signal to another computer, but for now i am only learning how to do this.
If not, what is the default depth of modulation for am here. In the context of radio communication, near the end of the 2oth century, few modulated signals contain a significant component at carrier frequency. The focus of this lab is to familiarize the student with the modulation and demodulation of an am signal. Amplitude modulation or am is a method to transmit signals via electromagnetic transmission. Demodulation is extracting the original informationbearing signal from a carrier wave. This principle is at the heart of amplitude modulation.
To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. In ask, the input binary signal is multiplied with the carrier signal along with its time intervals. Overmodulated am signals and its requirement for coherent detection are also considered. 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. 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. What is analog modulation and state various techniques. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn. The idea is simple, though the notion that it can be used to modulate signals. In this modulation, only half of the signal of the dsbsc is used. Matlab code for amplitude modulation am file exchange. The ad630 is a high precision balanced modulatordemodulator. In this lab, students investigate two methods to recover an amplitude modulation am signal in order to develop an understanding of the demodulation process in the time and frequency domain. But the width of each pulse is made properly proportional to the amplitude of the signal at that instant. Hi, i am new to labview and have been learning using tutorials that i find in here.
Terms like diode detector, synchronous detector and product detector are widely used. The modulation rate is typically much lower than the. The term detection is the older term dating back to the early days of radio. These methods contrast with amplitude modulation, in which the amplitude of the carrier wave varies, while the frequency and phase remain constant. From what i have read so far amplitude modulation with large carrier is favaroble because envelope detector can be used at the receiver to derive the message signal and therefore another mixer is not needed at the receiver. Some useful tutorials can be found on the ee 370 courselab website. 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 we were to implement every possible combination of demodulation algorithm, carrierrecovery technique, and clock regeneration as a distinct model, the combinatorial explosion of different models would become unmanageable. The process of demodulation for signals using amplitude modulation can be achieved in a number of different techniques, each of which has its own advantage. Laboratory manual principles of communication system lab ee226f ivth semester. 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. Chapter 6 doublesideband suppressedcarrier amplitude. A modem from modulatordemodulator can perform both operations.
The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. I am trying to create a vi that will input an audio signal from mydaq and do fsk modulation then demodulate and output using my laptop speakers. In amplitude shift keying theory, input binary signal amplitude varies according to the carrier signal voltage.
The process and the signal were called amplitude modulation, or am for short. If youve read the page on amplitude demodulation, the preceding paragraph may have caused you to realize that a quadrature demodulator is actually composed of two amplitude demodulators. But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. We can define amplitude modulation by saying that a modulating signal, should produce an am wave of the form well use s instead of v or e to indicate that were talking about a modulated quantity and that it can be either a field or a voltage. The lif port modification does not alter the standalone capabilities of the transceiver, but when it is connected to the computer, it creates a powerful ifsdr transceiver. M is the alphabet size and must be an integer power of 2.
The demodulation is performed by an envelope detector. This experiment examines the characteristics of the amplitude modulation am process. Read online modulation d amplitude demodulation d amplitude book pdf free download link book now. Each sideband is equal in bandwidth to that of the modulating signal. The process of amplitude modulation consists of the amplitude of the carrier wave being varied in sympathy with a modulating signal. Mqam modulation and demodulation file exchange matlab. Amplitude modulation early radio ee 442 spring semester. Therefore, when we receive the amplitude modulation signal, we need to restore the audio signal. The demod ulation is performed by an envelope detector. The carrier is usually a radiofrequency rf signal such as the 1. What is digital modulation and state various techniques. Both phase and frequency of carrier are known at the demodulator amplitude of.
I tried to explain the circuit connections that is needed for the experiment. Dsbsc modulation at a carrier frequency, kc, specified by the student. Amplitude modulation am, demodulation and their circuit. When expressed as a percentage it is the same as the depth of modulation.
Oct 30, 2017 amplitude modulation and demodulation. In practice, the demodulation of suppressed carrier amplitude modulated signals requires fairly. Telo, chapter 9, modulation, demodulation, signal sampling. The demodulator is the circuit, or for a software defined radio, the software that is used to recover the information content from the overall incoming modulated signal. From experiment 3, we know that the amplitude modulation signal utilizes the amplitude of audio signal to modulate high frequency carrier signal. The fmmodulated signal has its instantaneous frequency that varies linearly with the amplitude of the message signal. Is there a way i can vary it, say, to 100% modulation depth. The signal flow below shows how the bilif is connected and replaces the internal modulation and demodulation hardware. This is the same as the am modulation above but without the carrier. Brand, philips semiconductors, pcale qam demodulation.
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