Connections are made for the am modulator and demodulator as shown in the circuit diagrams. The receivers used to listen to amdsbc are perhaps the simplest receivers of any radio modulation technique. Zahid tufail 10el60 a device that performs modulation is known as a modulator and a device that performs the inverse operation of modulation is known as a demodulator sometimes detector or demod. 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. The carrier is usually a radiofrequency rf signal such as the 1. Amplitude modulation is one of the earliest radio modulation techniques. Indian institute of technology kanpur ee 381 electrical engineering labii 2003 04. Before we study in detail about pam lets know the concepts of modulation. If this minimum value is zero, the modulation depth is 100%. Overmodulated am signals and its requirement for coherent detection are also considered.
Report on this experiment should include the following. 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. Denote the maximum amplitude of the am signal as v p, then the capacitor discharge will follow the following equation vp. To study frequency modulation and determine its modulation factor 4. Compare your measurements to the theoretical values calculate them for your report 4. The lab 9 a measuring of the modulation depth via oscilloscope 9 b. Pulse amplitude modulation faculty of engineering and. Note that this is on the very low end of the recommended voltage range. 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.
Vary the modulating frequency and amplitude and observe the effects on the modulated waveform. This lab gives you the opportunity to actually work on amplitude modulation and reinforce the theory taught in class. The process and the signal were called amplitude modulation, or am for short. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. Indian institute of technology kanpur ee 381 electrical. To study amplitude demodulation by linear diode detector 3. Pulse amplitude modulation is the basic form of pulse modulation. The first is to gain experience in actually programming the usrp to act as a transmitter or a receiver. Amplitude modulation lab report and grading format 1 report format 1. Eee3208 communication theory lab ahsanullah university. Amplitude modulation is used to encode information in a highfrequency carrier by varying the amplitude of the carrier. Your report should contain the circuit schematic and the amplitude modulated signal output both in time and frequency domains generated by pspice.
The main difference in generating balanced amplitude modulation to standard amplitude modulation is the missing offset of the 1 offset in the modulating signal. In amplitude modulation, the amplitude of the carrier wave varies in accordance with the. As an example, the following figure shows the amplitude modulation with. An am modulator is constructed usingthe analog devices ad534 four quadrant multiplier, and the properties of the resultingsignal are examined using labview. Group3 umang gupta 2010ee50564 indrabhushan 2010ee50548 vivekmangal 2010ee50566 jitendra kumar meena 2009ee50483 12912 experiment 2. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. One of the simplest schemes for wireless communication is amplitude modulation am. 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. Aug 18, 20 eep306 lab report amplitude modulation submitted by.
The rate at which the amplitude of the carrier is changed is called the modulation rate. In this lab you will begin to look at the frequency power spectrum of signals. Each part may be of any convenient amplitude at the input to an adder. Amplitude modulation part 1 in class you have studied the theory of amplitude modulation. University of north carolina at charlotte department of. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. In this experiment, the properties and characteristics of amplitude modulated amsignals and their frequency spectra are examined. Labreport analogue communications amplitude modulation name. With the modulating voltage adjusted to zero amplitude, increase the carrier amplitude until v o has a value of 2 v pp. Teach online lab this is an online, interactive lab that contains instructions, multimedia, and assessments where students can learn at their own pace.
The digital modulation experiments include pcm encoding and decoding, line codes and digital. Lab 5 amplitude modulation and demodulation pages 1 7. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. The second is to investigate classical analog amplitude modulation and the envelope detector. It may be necessary to adjust the level and frequency of both v c and v m to achieve a suitable waveform and index of modulation. Modulation is a process by which characteristics of a highfrequency carrier signal are altered to convey information contained in a lowerfrequency message. Amplitude modulation the effect of percentage modulation depth of modulation to the am. The depth of modulation can be varied using the variable knob provided at a. You will construct a chopper modulator to generate am. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. This experiment examines the characteristics of the amplitude modulation am process. 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.
The purpose of this lab is for you to gain familiarity with the concepts of amplitude. Frequency of the input carrier is fixed at constant amplitude of 1. We also see how to use a balanced mixer to modulate a signal. Include in your report all the plots obtained during the lab. This lab introduces students to communications theory with amplitude modulation and demodulation. Amplitude modulation and demodulation the expression for an am waveform with carrier frequency. The analog modulation part covers the generation and detection of doubleside band suppressed carrier dsbsc modulation, doubleside band with carrier also known as am modulation, quadrature amplitude modulation qam, and frequency modulation.
The frequency of the modulation signal determines the rate of the frequency change from the center frequency. Postlab questions must be answered in each experiments laboratory report. The demodulation is performed by an envelope detector. The percentage modulation can be calculated using the formula. Lab report amplitude modulation free download as word doc. Modulation allows us to transmit multiple signals in the same medium i.
Amplitude modulated signal can be represented by the following equation. Amplitude modulation is used since the first days of the 20th century mainly for transmitting voice and signals through the conventional broadcast band like the long, medium and. Matlab code print the code for the following question with the report and also submit the. Frequency division multiplexing, fdma amplitude modulation and demodulation.
Experiment 1 design of conventional amplitude modulator. Show the resultsplots, you can use excel or a snap shot or draw it by hand. In your lab write up compare this with what is expected for a modulation depth of m 1. The spectrum of the dsbsc signal is the convolution of the input signal spectrum mf and the spectrum of the cos2 pft carrier. The amplitude of the fm signal is constant at all times and is independent of the modulation signal. In amplitude modulation, the amplitude of the carrier wave is made to vary in accordance with the message signal. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Increase the modulated signal until an am waveform appears.
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