Ok, we now know that frequency modulation generates side bands, and that the modulators frequency determines where they lie. Three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Frequency modulation is widely used for radio transmission due to the fact that the signaltonoise ratio snr is large in this method of modulation and hence radio frequency interference is minimized. Unit 9 week 8 delta modulation, differential pulse code. Perphase and space vector approaches to overmodulation, average voltages in a synchronously revolving dq reference frame, low frequency harmonic distortion. Introduction to pulse amplitude modulation, spectrum of pam signal and reconstruction, quantization. Operation of varying amplitude, frequency or phase of carrier signal accordingly with the instantaneous amplitude of the message signal is called modulation modulation adding information to a carrier signal. Sometimes the modulation index is denoted by the letters mf. Pulsed lasers are routinely operated in what is known as a quasicw mode in which the laser is pulsed at some typically high frequency. Chapter 6modulation techniques shandong university.
Load capacitor for crystal rf blocking coil rf rejection capacitor overview of fm modulation techniques modulator type short description advantages disadvantage block diagram key feature switched capacitor a chipinternal transistor is. Frequency modulation objectives upon completion of this chapter, the student should be able to. The subject of frequency modulation involves some con tradictions of existing practices and in general introduces new thoughts in connection with the operation of radio communication systems, transmitters and receivers alike. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value. Frequency modulation fm is the standard technique for highfidelity communications as is evident in the received signals of the fm band 88108 mhz vs. Spectra have a typical trapezoidal shape in linear frequency and amplitude in decibels. Download fulltext pdf download fulltext pdf gearbox vibration signal amplitude and frequency modulation article pdf available in shock and vibration 194. Hapter modulation and demodulation mit opencourseware. Therefore we only consider the case where the message signal mtis a sinusoidal signal. Sound transmission in air has limited range for the amount of power your lungs can generate.
Angle modulation continuing from chapter 3, we now focus on the tterm angle in the general modulated carrier waveform x c. Both amplitude and phase of ft carry information of ft. Uses the 5bit baudot encoding invented in 1870 this is the origin of the word baud. There actually are practical differences between the two. If there are more doubts, please feel free to request t. Each radio station is assigned 200 khz, to transmit a stereo audio.
Lecture 36 noise in phase and frequency modulation systems. The big advantage of frequency modulation is its noise reduction ability, because most of noise is appeared as additional amplitude and in fm the amplitude of signal is hold fixed. Modification in phase according to low frequency will give phase modulation. Modulation is a nonlinear effect in which several signals interact with one another to produce new signals with frequencies not present in the original signals. Digital modulation 1 lecture notes ingmar land and bernard h. Phase modulation pm is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave. Delta modulation, differential pulse code modulation.
In this lesson, these modulation techniques are introduced. Frequency modulation equations formulas bessel rf cafe. Unit 8 week 7 signal reconstruction from sampled signal. Has a shift to figures character that changes what the codes mean so numbers and punctuation can be sent, and of course a shift. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Fleury navigation and communications navcom department of electronic systems aalborg university, dk version. Unit 7 week6 narrowband fm generation, spectrum of fm. Unit 4 week3 power efficiency, dsbsc modulation and. 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.
In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal. Set g so that the sinewave peaks just fall to zero. To extend the range your voice can reach, we need to. Frequency modulation is the process in which the frequency of the carrier signal is varied by the modulating signal while the amplitude remains constant. Frequency modulation, fm, variation of the frequency of a carrier wave in accordance with the characteristics of a signal. 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. Frequency modulation techniques infineon technologies. Frequency modulation create signals whose frequency is timevarying a chirp signal is a sweptfrequency signal whose frequency changes linearly from some low value to a high one. Discuss the differences between am and angle modulation. Modulation presented by nidhi baranwal mca 6th sem 2. Unit 5 week4 quadrature carrier multiplexing qcm and. Introduction manner in which it differs from amplitude modulation, and details associated with f m receiver servicing problems.
Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses. Frequency modulation is a form of modulation, which represents information as variations in the instantaneous frequency of a carrier wave. Lec 45 principles of communication systemsi delta modulation, onebit quantizer iit kanpur duration. Since frequency modulation is a nonlinear process, an exact description of the spectrum of an frequencymodulated signal for an arbitrary message signal is more complicated than linear process. What is the difference between phase modulation and. Amamplitude modulation fmfrequency modulation pmphase modulation in phase modulation, modulation index is directly proportional to modulating voltage only while in frequency modulation, modulation index is also inversely proportional to modulat. Communication engineering nptel online videos, courses. An introduction to frequency modulation sound on sound.
Calculate modulation index, signal bandwidth, sideband frequencies and. There is a special case concerning modulation index, and this is when the frequency of the modulating audio is at its highest. Surendra prasad, department of electrical engineering,iit delhi. Noise effects arising from demodulation is one difference. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Gearbox vibration signal amplitude and frequency modulation.
Frequency modulation definition and meaning collins. We therefore assume mta mcos2 f mtfor pm and mta msim2 f mtfor fm. Angle modulation nptel pdf understanding frequency modulation fm, frequency shift keying fsk, sundes any modulation method that changes the angle instead of the amplitude is. Explain the advantages and disadvantages of the different analog modulation techniques.
This is the simplest form of modulation where the amplitude of the carrier wave is modulated by the analog signal known as the modulating signal. Weexpresstheresultinganglewe express the resulting anglemodulatedwaveasmodulated wave as 4. Nptel video lectures, iit video lectures online, nptel youtube lectures. 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.
Dey, department of electrical engineering,iit bombay. Modulation for analog nyu tandon school of engineering. Using amplitude modulation to shift the baseband signal fm radio 88mhz108 mhz. Frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt. In both cases the waves frequency and phase vary from moment to moment. Rtty radioteletype is a very old fsk mode that printed digital messages out onto paper. There are many forms of modulation, including frequency and amplitude. Phase modulation of the carrier with a message signal is equivalent to frequency modulation of the carrier with the derivative of the message signal. Lecture series on communication engineering by prof. Frequency modulation, phase modulation, and fm spectra. The spectral efficiency of single sideband ssb modulation is.
Fm signals are used in technology such as radars, telemeters, eeg, radio broadcasting, satellite communication and magnetic tape recording systems. Fm modulated signal st is a nonlinear function of the modulating signal mt, thus it is known as nonlinear modulation process. For the love of physics walter lewin may 16, 2011 duration. The transmission bandwidth required by dsb sc is b t2b. Frequency modulation uses the instantaneous frequency of a modulating signal voice, music, data, etc. The higher frequency signal indicates a mark and the lower indicates a space. Frequency versus amplitude modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. Digital communication nptel online videos, courses iit. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is sinusoidal. 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.
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