Modulation atcm in abdominal mdct examination while maintaining optimum image quality for diagnosis. Modulation presented by nidhi baranwal mca 6th sem 2. Weexpresstheresultinganglewe express the resulting anglemodulatedwaveasmodulated wave as 4. Nptel syllabus circuits for analog system design video course course outline introduction to linear ic applications. This video discusses basics of frequency modulation which includes definition of frequency modulation and also frequency modulated waveform. Therefore we only consider the case where the message signal mtis a sinusoidal signal. Therefore, frequency deviation, the formula for bandwidth of wide band fm wave is. As mentioned earlier, the amplitude is kept constant.
A continuous wave modulation method, which varies frequency in proportion to the amplitude of the modulating signal. Invented by major edwin howard armstrong, also known for two other key innovations, superheterodyning and regeneration, frequency modulation is the basis for most common wireless communications technologies, from radio and television to wireless lan. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is sinusoidal. Lecture 28 modulation techniques for mobile communications. Phase modulation of the carrier with a message signal is equivalent to frequency modulation of the carrier with the derivative of the message signal. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses, youtube iit videos nptel courses. There is a special case concerning modulation index, and this is when the frequency of the modulating audio is at its highest.
Wireless communication nptel online videos, courses. Communication engineering nptel online videos, courses. In frequency modulation, the instantaneous frequency of the radiofrequency wave is varied in accordance with the modulating signal, as shown in view a of figure 25. Sometimes the modulation index is denoted by the letters mf. 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. The number of times per second that the instantaneous frequency is varied from the average carrier. Digital communication nptel online videos, courses iit. Lecture series on communication engineering by prof.
Why does channel length modulation occur in mosfets. Video modulation is a strategy of transmitting video signal in the field of radio modulation and television technology. These techniques are also called as digital modulation techniques digital modulation provides more information capacity, high data security, quicker system availability with great quality communication. If there are more doubts, please feel free to request t. Use modulation to shift the signal essentially in front of the filter. This results in oscillations similar to those illustrated in view b. Spectra have a typical trapezoidal shape in linear frequency and amplitude in decibels.
Frequency modulation is the process in which the frequency of the carrier signal is varied by the modulating signal while the amplitude remains constant. 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. 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. Digital modulation provides more information capacity, high data security, quicker system availability with great quality communication. Ranjan bose, department of electrical engineering, iit delhi. 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. Fm modulated signal st is a nonlinear function of the modulating signal mt, thus it is known as nonlinear modulation process. This strategy enables the video signal to be transmitted more efficiently through long distances.
So weve worked our way through modulation with a complex exponential carrier. The varying in mas values according to acs for different body counter of the patients was observed. One being modulation with a cosine, and the other, modulation with a sine. Hence, digital modulation techniques have a greater demand, for their capacity to convey larger amounts of data than analog ones. Narayanan,department of electrical engineering,iisc bangalore.
There are many forms of modulation, including frequency and amplitude. Angular tube current modulation is an aec feature that adjusts the tube current as the xray tube rotates around the patient to compensate for attenuation changes with view angle angular tube current modulation is used to adjust the tube current to attempt to. Pulse width modulation for power electronic converters by dr. Digital modulation 1 lecture notes ingmar land and bernard h. Introduction manner in which it differs from amplitude modulation, and details associated with f m receiver servicing problems. In general, video modulation means that a higher frequency carrier wave is modified according to the original video signal. Ok, we now know that frequency modulation generates side bands, and that the modulators frequency determines where they lie. Pulsed lasers are routinely operated in what is known as a quasicw mode in which the laser is pulsed at some typically high frequency. Lec 45 principles of communication systemsi delta modulation, onebit quantizer iit kanpur duration. Modulation effects are the bane of the audio engineer, for they produce intermodulation distortion, which is annoying to the music listener.
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. 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. Frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt. 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. Digitaltoanalog signals is the next conversion we will discuss in this chapter. And what we saw, among other things with a complex exponential carrier, is that what it corresponds to is two branches. Phase modulation pm is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave. F or p ositiv e halfcycles of c t d1 and d3 conduct, d2 and d4 op en. Frequency modulation, phase modulation, and fm spectra. Modification in phase according to low frequency will give phase modulation. Frequency modulation definition and meaning collins. We therefore assume mta mcos2 f mtfor pm and mta msim2 f mtfor fm. Fleury navigation and communications navcom department of electronic systems aalborg university, dk version.
In words, the angle is used to carry information in 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. Gearbox vibration signal amplitude and frequency modulation. Download fulltext pdf download fulltext pdf gearbox vibration signal amplitude and frequency modulation article pdf available in shock and vibration 194.
Fm signals are used in technology such as radars, telemeters, eeg, radio broadcasting, satellite communication and magnetic tape recording systems. Unique features 23 stress in simple english words i. Hence, digital modulation techniques have a greater demand, for their capacity to convey larger amounts of. Nptel syllabus pulse width modulation for power electronic converters video course course outline converter topologies for acdc and dcac power conversion, overview of applications of voltage source converters.
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