The process of separating or extracting the modulation from a signal is called demodulation or detection. In am radio broadcasts, is the audio signal being transmitted usually bandlimited to less than 10 khz, and is the channel center frequency that one dials up. Is there a way i can vary it, say, to 100% modulation depth. The carrier signal and y have sampling frequency fs. 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. Nevertheless, as previously mentioned, pspwm and h2pwm methods result in higher distortion of the output linetoline voltages when compared with rlspwm schemes especially at low amplitude modulation term m. Amplitude modulation with simple am radio transmitter duration. I want to do amplitude modulation of an audio signal. Bpsk stands for binary phase shift keying, qpsk stands for quadrature phase shift keying and qam quadrature amplitude modulation. For amplitude modulation, we use simple and low cost circuit. Each channel sharing scheme a set of basis vectors. Wave fundamentals and modulation demonstration board.
It provides link to download labview vi source code. Am modulation and demodulation with circuit and output 1. Then, students will use labview to program an am demodulator and use it to explore and visualize the effects of the modulation coefficient on the quality of the. I might give labview a shot my uni gives us free access in case it cant be done on matlab. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Analog modulation and demodulation amplitude modulation pages 306309. Software defined radio am modulation and demodulation duration. 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. Vsb modulation with envelope detection is used to modulate image in analog tv signals. Aly elosery october 25, 2010 this lab is divided into two parts. Pulseamplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Hi, im a beginner in matlab and im just wondering whether the modulation constant. The purpose of this board is to give the instructor a ready instructional resource to support lesson presentations in wave fundamentals and modulation. I am new to labview, i have tried to perform amdsb modulation using modulation toolkit, but the result is very strange, when i change the modulationg signal frequency, the caries frequency changes, and when i change the amplitude of modulating signal the result is very strange, maybe i am doing some mistake, so please guide me.
Pdf a set of labviewbased virtual tools for communication. This amplitude modulation is tested in ni usrp rio 2920 as transmitter. The process of demodulation for signals using amplitude modulation can be achieved in a number of different. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Am modulation of audio file matlab answers matlab central. You control the number of samples, message signal frequency hz, duration sec, and the type of waveform used for the message signal.
Modulator and demodulator labview vibpsk,qpsk,16qam,64qam. This paper discusses modulation techniques with the labviewbased rf communications package, developed for the illustration of different. Demodulation is the process by which the original information bearing signal, i. This gives us something to modulate and carry the information pattern from. That these amplitude modulations can be demodulated using an envelope detector. 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. The process of digital demodulation involves matched filtering, symbol timing extraction. Why frequency modulation is better than amplitude modulation. Amplitude modulation modulation is the process of varying a higher frequency carrier wave to transmit information. The 9410 am dsb ssb generator controls and connectors carrier level changes the level of the carrier when using am. In this video you will see amplitude modulation using different type of signals and channels. For amplitude modulation, the process of demodulation or detection can be accomplished very simply using a diode, or it may be achieved in other ways that provide more effective demodulation of the waveform. Pdf an analog method to modulate and demodulate signals is.
Amplitude modulation financial definition of amplitude. You can also control the carrier phase rad and the amplitude of the added white noise. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Hapter modulation and demodulation mit opencourseware. This step is the opposite of modulation and refers to the process required to extract the original information signal from the modulated signal. Amplitude demodulation matlab amdemod mathworks india. Then, students will use labview to program an am demodulator and use it to explore and visualize the. If the amplitudemodulated signal shown here is passed through a frequency analyzer, the following spectrum is the result. Demodulation labview modulation toolkit documentation. Amplitude modulation and demodulation national instruments. You should also see why this form of detector suffers from ripple and negative peak clipping. Am modulation and demodulation with circuit and output. Demodulation uses either standard am or dsbsc demodulation, depending on whether a carrier tone is transmitted. The message signal is, for example, a function of the sound to be reproduced by a.
That amplitude modulation uses variations in the carrier size to convey information. Learn more about modulation, amplitude, signal processing, audio. 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. Feb 07, 2020 amplitude modulation and demodulation lab communication engineering notes edurev is made by best teachers of. 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. Am works by varying the strength amplitude of the carrier in proportion to the waveform being sent. Watch other videos like ask and fsk video also i provide the videos in endscree.
This lab introduces students to communications theory with amplitude modulation and demodulation. Dsb sc modulation and demodulation using ni labview youtube. Introduction to communication systems using national. Amplitude modulation is a powerful tool that allows you to create and play new sounds that you cannot obtain using conventional oscillators alone. To produce dsbsc and ssb change the carrier level to min.
Amplitude modulation am, demodulation and their circuit. Sinusoidal amplitude modulation am mathematics of the dft. This page of labview source code covers modulator labview vi and demodulator labview vi. The national instruments nielvis set and the labview student edition. Amplitude modulation or am is a method to transmit signals via electromagnetic transmission.
Though it is theoretically possible to transmit baseband signals or information without modulating it, it is far more efficient to send data by modulating it onto a higher frequency carrier wave. Amplitude modulation can be produced in various ways. Note that this is on the very low end of the recommended voltage range. This example demonstrates generation and demodulation of a simulated double side band dsb am signal. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Page 1 of 7 revision c lab 5 amplitude modulation and demodulation prelab 5. It covers bpsk, qpsk, 16qam and 64qam modulation techniques. This is true even though everything we have discussed assumes that we have used simple sine waves as our input signals. 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. Monitoring the spectrum with ni usrp and labview spectrum monitoring example vi. That one way of am modulating a wave is to use a square law device such as an fet.
Spectral measurements toolkit user guide, installed in pdf format at startall. Lab 5 amplitude modulation and demodulation pages 1 7 text. Then, students will use labview to program an am demodulator and use it to explore and visualize the effects. An analog method to modulate and demodulate signals is presented in this short paper. The ni labview modulation toolkit contains vis that can be used with. A represents the carrier amplitude, which is a constant that demonstrates the modulation index. Yet, am continues to be used today in many communication applications. Here well use the example of a square law fet as illustrated in figure 9. The board would be used in conjunction with a projection capable oscilloscope and an. What is analog modulation and state various techniques. The ni labview modulation toolkit help provides information about how to use the toolkit in labview to generate and analyze analog and digitally modulated signals. What we do in am, very roughly,is to throw away the frequency content of. Amplitude modulation matlab code download free open. 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.
The downconverted signal undergoes a demodulation process. Any din scheme uses a finite number of distinct signals to represent digital data. Content introduction what is modulation types of modulation amplitude modulation modulation index amplitude demodulation circuit diagram about project conclusion 3. Amplitudeshift keying ask is a form of modulation that represents digital data as variations in the amplitude of a carrier wave. Simulation of analog modulation and demodulation techniques in. Pdf simulation of analog modulation and demodulation. The ideal modulated signal should have a minimum euclidean distance of 2. 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.
Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. 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. Wave fundamentals and modulation demonstration board purpose. Vsb signals are generated using standard am or dsbsc modulation, then passing modulated signal through a sideband shaping. 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. The modulated signal y has zero initial phase and zero carrier amplitude, resulting from a. Because of amplitude modulation wavelength, am signals can propagate longer distances. It is assumed that and that amplitude modulation is formed by the product. Amplitude modulation and demodulation lab communication. Amplitude modulation definition of amplitude modulation.
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