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