Amplitude modulation am is similar to dsb but has the advantage of permitting a simpler demodulator, the envelope detector. 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. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. It is still in use today in a variety of systems, including, of course, am broadcast radio. Science only amplitude phase and frequency of the wave can be changed so we have three basic type of modulation 1. Quadrature amplitude modulation is widely used for carrying many digital signals, everything from wifi to mobile phone communications and very much more. The autocorrelation of a stationary random process, which was discussed. The resulting amplitude modulation am waveform is then demodulated. 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. Here amplitude of rf carrier is varied in accordance with amplitude of modulating signal input.
Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. Pcm is in binary form,so there will be only two possible states high and low 0 and 1. Jun 03, 2016 this paper focuses on the binary phase shift keying digital modulation technique for noiseless and noisy transmission with the following objectives. Amplitude, frequency and phase modulation can be applied directly by software to the generated signals, which gives great flexibility where complicated and precise waveforms are required. The transmission of a wave signal by modulating the amplitude of the signal is amplitude modulation. Since the frequency change of a sinusoid in time results in alternation of phase in time, fm may also be referred to as phase modulation, or pm, as well. This form of modulation is essentially derived from two carriers that are 90 out of phase and adding information, either analogue or digital. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. Binary phase shift keying digital modulation technique for. The effect of amplitude modulation index and frequency modulation index on total harmonic distortion in 1phase inverter to cite this article. Here frequency of rf carrier is varied in accordance with frequency of modulating signal input.
Amplitude modulation am is a modulation technique where the. We also see how to use a balanced mixer to modulate a signal. Frequency division multiplexing, fdma amplitude modulation and demodulation. To study amplitude demodulation by linear diode detector 3. This gives us something to modulate and carry the information pattern from. Complex exponential and sinusoidal amplitude modulation. Both modulated carriers are summed to result in a signal with amplitude and phase modulation.
Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. Quadrature amplitude modulation qam is a modulation scheme that moderates two sinusoidal carriers 90 outofphase with each other. 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. In chapter 6, we will discuss am and other modulation systems and will illustrate them with matlab. We can also get back our analog signal by demodulation.
Pulse amplitude modulation pam theory of and its applications. More complete discussions of am and analog implementa tions can be. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Amplitude modulation an overview sciencedirect topics. Ssb generator and the am dsb receiver, as well as terminology used in amplitude modulation. Overmodulated am signals and its requirement for coherent detection are also considered. In high level amplitude modulation system, modulation is done at high power of carrier and modulating signals so power amplifiers are used to boost the carrier and modulating signals before modulation.
Frenzeljr, in handbook of serial communications interfaces, 2016. To study sampling and reconstruction of pulse amplitude modulation system 6. This principle is at the heart of amplitude modulation. We are only going to discuss the ring modulator because it is the.
The second is to investigate classical analog amplitude modulation and the envelope detector. Wideband interference in the vicinity of 38753900 kcs. This makes the problem of am more difficult to identify and it can often be missed by those investigating noise complaints if residents descriptions of the noise do not match those that the investigator considers relate to am. What this means that we only modulate that is increasing or decreasing the amplitude of the wave to be transmitted as a signal so as to not affect its content but. In this discussion, we focus on amplitude modulation only. However, this conclusion leaves the possiblity that dis tortions which are insigni.
Indian institute of technology kanpur ee 381 electrical. Amplitude modulation can be produced in various ways. Pulse amplitude modulation an overview sciencedirect topics. Amplitude modulation circuit implementation for use in. Modulation allows us to transmit multiple signals in the same medium i. Amplitude modulation early radio ee 442 spring semester. The standard form of an amplitude modulated am wave is defined by. 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. Here well use the example of a square law fet as illustrated in figure 9. A type of dsb, called binary phaseshift keying, is used for digital telemetry. The amplitude of the fm signal is constant at all times and is independent of the modulation signal. In particular, we discuss amplitude and frequency modulation. This electrical signal is called the message or baseband signal.
Yet, am continues to be used today in many communication applications. The demodulation is performed by an envelope detector. The components of each carrier are called inphase and quadrature. The frequency of the modulation signal determines the rate of the frequency change from the center frequency. To study frequency modulation and determine its modulation factor 4. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Although modulation index is related to percentage of modulation as discussed below, section 73. Amplitude modulation is a modulation system in which the carrier wave has its. The message signal is then used to electrically vary the amplitude. Figure 1 shows four different waveforms corresponding to the above equation with varying values of m. Amplitude modulation discussion document 3 wind farm noise and am can be described in a variety of ways. Collector modulation method is the example of high level amplitude modulation. Note that this is on the very low end of the recommended voltage range. Pulse code modulation is a method that is used to convert an analog signal into a digital signal, so that modified analog signal can be transmitted through the digital communication network.
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. In amplitude modulation, it is the voltage level of the signal to be transmitted. Double sideband dsb is one of the easiest modulation techniques to understand, so it is a good starting point for the study of modulation. What is amplitude modulation, am electronics notes. The amplitude of the modulation signal determines the amount of the frequency change from the center frequency.
Experiment 5 amplitude modulation preliminary discussion in an amplitude modulation am communications system, speech and music are converted into an electrical signal using a device such as a microphone. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. A brief discussion about pulse code modulation and demodulation. Am and fm both are used as analog modulation techniques. As we will see, modulation techniques not only allow us to. Amplitude modulation part 1 in class you have studied the theory of amplitude modulation. If this minimum value is zero, the modulation depth is 100%. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam.
Amplitude modulated signal can be represented by the following equation. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Modulation is a technique by which we can transfer our information at a distance. Course projects are one of the seven high impact practices discussed by koh in 1. An am wave may thus be dscribed, in the most general form, as a function of time. Before we study in detail about pam lets know the concepts of modulation. Introduction the process of changing some characteristic e.