Signals that occupy the same range of frequencies can be separated modulation helps in noise immunity, attentuation depends on the physical medium figure 1 shows the different kinds of analog modulation schemes that are available. Communication theory frequency modulation exam study. These videos explain you what is modulation, different kinds of modulations like amplitude modulationam and frequency modulationfm,qpsk,qam,phase modulat. Communication systems a lecture notes by mahesh lohith k. Now let us look at one of the techniques to achieve. Questions from video lectures of nptel sl no questions video number time in minutes 1 give some examples for the communication systems which use space as the channel. Recall, the bandwidth of a complex signal like fm is the difference between its highest and lowest frequency components, and is expressed in hertz hz.
Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. The process by virtue of which some characteristic, normally amplitutude, frequency, phase of a voltage signal is varied in accordance to the instantaneous value of some other voltage signal called carrier need of modulation. Pulse modulation timedivision multiplex tdm continued advantages of tdm the circuitry required is digital, thus affording high reliability and efficient operation. Surendra prasad, department of electrical engineering,iit delhi. Fm does not touch the amplitude of the carrier and. In frequency modulation fm, unlike am, the amplitude of the carrier is kept constant, but its frequency is altered in accordance with variations in the audio signal being sent.
All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. This video will help you to understand the expression of phase modulation, use of phase modulation, working of phase modulation. Principles of communication modulation tutorialspoint. The amount of decrease or increase around fc is called the frequency deviation. The analysis of these power circuits are presented in detail along with the waveforms and control techniques. Next month, well take a closer look at some practical aspects of frequency modulation, and introduce the idea of operators a common.
Frequency modulation is a powerful method of synthesis that is as relevant to analogue synthesizers as it is to digital ones, and which is capable of generating sounds unobtainable by any other method. In this second experiment, we will examine the most common modulation scheme in daily life, namely, the. Chapter 2 concerns all the general problems of frequency modulation, while chapter 3 deals with the propagation distortion, which is apparent in a variablevelocity guided transmission channel, and, which appears on an echoing path either in free space, or over a badly matched feeder. Spectrum of fm signals, carsons rule for fm bandwidth. Download ac unit 4 ac notes analog communication pdf free download unit v angle modulation methods.
This site is like a library, use search box in the widget to get ebook that you want. For successful transmission and reception of information. Complex waveforms iii frequency modulation basicsynth. As we have seen in this document, frequency modulation can be simplified to angle modulation with a simple integrator. Modulation translates the signal from one region of frequency domain to. Principles of communication modulation a signal can be anything like a sound wave which comes out when you shout. Frequency modulation fm is the method of conveying informations over a carrier wave by varying its frequency. Angle modulation provides the improved noise performance. Example commercial fm signals use a peak frequency deviation of. Phase modulation, and frequency modulation are both the modulation techniques analyzed in angle modulation. This shout can be heard only up to a certain distance. Besides, it is simpler than the modulators and demodulators required in frequencydivision multiplexing fdm.
Modulation modulation is a process that causes a shift in the range of frequencies in a signal. We will get the percentage of modulation, just by multiplying the modulation index value with 100. This form of modulation was developed by the american electrical engineer edwin h. This is different from the amplitude modulation am in which the amplitude of the carrier wave is varied while its frequency remains constant. Frequency modulation an overview sciencedirect topics. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. The spectrum of an fm signal is quite complicated and is dependent on mf. But pm and fm are not exactly equivalent, especially inanalog applications. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Frequency modulation software free download frequency modulation top 4 download offers free software downloads for windows, mac, ios and android computers and mobile devices.
Gate preparation, nptel video lecture dvd, electronicsandcommunicationengineering, communicationtheory, frequencymodulation, amplitude modulation, am wave, am. Amplitude modulation double side band nptel mafiadoc. Amplitude modulation and frequency modulation youtube. Pdf communication systems a lecture notes by mahesh. Frequency modulation is a form of modulation, which represents information as variations in the instantaneous frequency of a carrier wave. When theinstantaneous phase of a carrier is varied, the instantaneous frequency changes as well. Phase modulation is similar in practice to frequency modulation. Modulator frequency is specified as a multiple of the carrier in the range 010 and may be harmonic integer values or inharmonic real values. Lecture series on communication engineering by prof. Multiple choice questions and answers on frequency modulation. Frequency modulation fm is an important modulation scheme both because of its widespread commercial use, and because of its simplicity. Meaning, pronunciation, translations and examples log in.
Modulation index of an fm wave the modulation index is the ratio of the amount of frequency deviation to the audio modulating frequency. There is another way of modulating a, sinusoidal carrier wave, namely, angle modulation in which the angle of the carrier wave is varied according to the baseband signal. Before we start discussing fm modulation we take a look at some important terms. 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. In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal. Frequency and phase modulation sharlene katz james flynn overview history why fm. Introduction to pulse amplitude modulation, spectrum of pam signal and.
The goal of this experiment is to become familiar with fm modulation and demodulation. In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique. Click download or read online button to get frequency modulation book now. The envelope generators are adsr types with attack and decay rates in the range 01 second. Frequency modulation is the process in which the frequency of the carrier signal is varied by the modulating signal while the amplitude remains constant. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Gate preparation, nptel video lecture dvd, electronicsandcommunicationengineering, communicationtheory, frequency modulation, amplitude modulation, am wave, am. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Frequency modulation fm angle modulation fm and pm spectral characteristics of fm signals fm modulator and demodulator lin dai city university of hong kong ee3008 principles of communications lecture 4. When the instantaneous frequency is varied, theinstantaneous phase changes. If you fourier analyse the frequencyamplitude modulated signal, you will notice that the power spectrum initially is a single peak that becomes wider and develops side bands with increasing. Am has only two sidebands usb and lsb and the bandwidth was found. Frequency modulation definition and meaning collins.
Fm concepts explained what is frequency modulation. Pdf analog communication system pdf notes ac notes sw. Okay so in the last class probably we have already started discussing about fm bandwidth so let us just explore a. In telecommunications and signal processing, frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave in analog frequency modulation, such as fm radio broadcasting of an audio signal representing voice or music, the instantaneous frequency deviation, the difference between the frequency of the carrier and its center.
Principles of communication part i professor aditya k. Frequency modulation fm in frequency modulation, the frequency rather than the amplitude of the carrier wave is made to vary in proportion to the varying amplitude of the modulating signal, as shown in fig. Modulation index, frequency deviation and phase deviation in fm and pm duration. The modulation index or modulation depth is often denoted in percentage called as percentage of modulation. Frequency modulation software free download frequency. Phase modulation is a modulation pattern for conditioning communication signals for transmission. An introduction to frequency modulation sound on sound.
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