Pdf a recently rediscovered sound synthesis method, which is based on feedback amplitude modulation fbam, is investigated. The message signal is, for example, a function of the sound to be reproduced by a. In amplitude modulation theory, the amplitude of a carrier signal is varied by the modulating voltage, whose frequency is invariably lower than that of the carrier. The amplitude modulation and demodulation technique involved in this project comprises of three stages. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. 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. Modulation is a process by which characteristics of a highfrequency carrier signal are. Use the spectrum analyzer to compare this modulator to the one in part 2. The idea is simple, though the notion that it can be used to modulate signals.
Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Introduction the process of changing some characteristic e. Pdf feedback amplitude modulation synthesis researchgate. 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. Introduction for am signals, the information is carried by the amplitude or envelope of the signal. We also see how to use a balanced mixer to modulate a signal.
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. 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. Vary the modulating frequency and amplitude and observe. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. Amplitude modulation am is an analog modulation scheme where the amplitude a of a fixedfrequency carrier signal is continuously modified to represent data in a message.
A represents the carrier amplitude, which is a constant that demonstrates the modulation index. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The demodulation is performed by an envelope detector. Jul 30, 2019 amplitude modulation is used in computer modems, vhf aircraft radio, and in portable twoway radio. Indian institute of technology kanpur ee 381 electrical. Each radio station is assigned 200 khz, to transmit a stereo audio. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In this project, a double sideband large carrier waveform is produced using a simple switching modulator circuit. Amplitude modulation an overview sciencedirect topics. In practice, the carrier may be highfrequency hf while the modulation is audio.
These form some of the main uses of amplitude modulation. This is accomplished by heterodyning the intelligence frequency with the carrier frequency. Amplitude modulated signal can be represented by the following equation. In an amplitude modulation am communications system, speech and music are converted into an electrical signal using a device such as a microphone. Pradeep kshetrapal, tutorials point india private limited. This principle is at the heart of amplitude modulation. In this type of modulation, the frequency of the carrier signal varies in accordance with the message signal, and other parameters like amplitude and phase remain constant. Then we will compare those results with findings on the coding of amplitude and frequency modulation in the auditory system. It is assumed that and that amplitude modulation is formed by the product. This report documents the development of one component of an uninterruptible power supply, the dctoac inverter.
Figure 1 shows four different waveforms corresponding to the above equation with varying values of. Since these side bands are always present in amplitude modulation, the am wave consists of a center frequency, an upper sideband frequency, and a lower sideband frequenmcy. Figure 1 below shows a simple message signal and an unmodulated carrier. In general, amplitude modulation definition is given as a type of modulation where the amplitude of the carrier wave is varied in some proportion with respect to the modulating data or the signal. The carrier usually has a frequency that is much higher than the messages frequency. 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. Am is widely used for the transmission of data in everything from short range wireless links such as wifi to cellular telecommunications and much more. View amplitude modulation research papers on academia. This technical report was prepared on behalf of the am improvement committee of the national association of. Remember, for analysis purposes keep the modulation index and frequency the same as part 2, step 3. The measurement and definition of amplitude modulations. Explain briefly in your report how amplitude modulation is accomplished by this circuit.
Matlab code print the code for the following question with the report and also submit the. Build simple envelope detector for am demodulation. This electrical signal is called the message or baseband signal. Am demodulation amplitude modulation refers to any method of modulating an electromagnetic carrier frequency by varying its amplitude in accordance with the message intelligence that is to be transmitted. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. 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. Pulse width modulation and in position ppm, pulse position. Amplitude modulation definition, types, solved examples. 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 early radio ee 442 spring semester. 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. This report specifically concentrates on the work considering appropriate metrics with which to measure amplitude modulation. What is amplitude modulation, am electronics notes. Es442 lab 4 amplitude modulation and demodulation i.
Amplitude modulation part 1 in class you have studied the theory of amplitude modulation. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. This experiment examines the characteristics of the amplitude modulation am process. Aug 18, 20 it is assumed that and that amplitude modulation is formed by the product. Through the use of analog signal processing techniques, a prototype which efficiently and accurately emulates the. Amplitude modulation theory frequency spectrum power. Amplitude modulation lab report and grading format 1 report format 1. This lab gives you the opportunity to actually work on amplitude modulation and reinforce the theory taught in class. Hence balanced amplitude modulation can be described as. Figure 1 shows four different waveforms corresponding to the above equation with varying values of m. This is accomplished by heterodyning the intelligence frequency with. Overmodulated am signals and its requirement for coherent detection are also considered. Note that this is on the very low end of the recommended voltage range. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam.
The process and the signal was called amplitude modulation, or am. Introduction what is communication transmitter channel receiver a communication system process of conveying message or information transmitter modifies the message signal into a form which is suitable for transmission over channel which is achieved by modulation information source. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Using amplitude modulation to shift the baseband signal fm radio 88mhz108 mhz. There are many ways to detect the envelope of am signals. First we will report psychoacoustical data on the detection of sinusoidal amplitude and frequency modulation in a songbird, the european starling. The message signal is then used to electrically vary the amplitude. The left and right channels each limited to 15khz are multiplexed into a single baseband signal using amplitude modulation using frequency modulation to shift the baseband. There are no amplitude scales shown, but you should be able to deduce the depth. Observe the modulator output signal at am op spring by making necessary changes in a. Objectives a to study and evaluate on the modulated am wave. An am wave may thus be dscribed, in the most general form, as a function of time as follows.
The message signal is then used to electrically vary the amplitude of a pure sinewave called the carrier. In this video, i have explained amplitude modulation by following outlines. Yet, am continues to be used today in many communication applications. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Jun 17, 2018 in this video, i have explained amplitude modulation by following outlines. The standard form of an amplitude modulated am wave is defined by. Include in your report all the plots obtained during the lab. Although modulation index is related to percentage of modulation as discussed below, section 73. Amplitude modulation is used in computer modems, vhf aircraft radio, and in portable twoway radio. The radio wave was called a carrier, since it was seen to carry the speech information with it. Build simple am modulator by using crystal oscillator. 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.
As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. The carrier frequency, fc, should be larger than the highest spectral component. The amplitude of each of these is constant in value but the resultant wave. Then we will compare those results with findings on the coding of amplitude and frequency modulation in the auditory system of the european starling and other bird species. The main difference in generating balanced amplitude modulation to standard amplitude modulation is the missing offset of the 1 offset in the modulating signal. There are a variety of modulation schemes available for both analog and digital modulation. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation. Effectively it is formed by having two carriers 90 out of phase. Show the resultsplots, you can use excel or a snap shot or draw it by hand. On spectral analysis with missing observations and. Pulse amplitude modulation pam theory of and its applications. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone line or radio.
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