The basic types of modulation are angular mo dulation including the special cases of phase and frequency modulation and amplitude modulation. This definition for is used to simplify the spectra of the modulated carrier by using bessel functions of the first kind besselj in mathematica with defined as above, the modulated carrier can now be defined as, where is the modulation index, is the carrier. Since frequency modulation is a nonlinear process, an exact description of the spectrum of an frequency modulated signal for an arbitrary message signal is more complicated than linear process. Lab manual frequency modulation experiment 8 experiment 2 phase look loop. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. First of all low pass filteris the, which is used to remove the noise in the audio signal. Lab 6frequency modulation formal report required groups of two this lab will have you create and analyze some simple frequency modulated fm waveforms. Amplitude modulation is defined as a process in which the amplitude of the carrier wave. The main advantage is the pcm modulation only needs 8 khz sampling frequency to maintain the original quality of audio. Analog transmission modulation frequency modulation. An introduction to frequency modulation sound on sound.
This is a laboratory manual for analog communication experiments. Pcm modulation is commonly used in audio and telephone transmission. 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 its most general sense, modulation means using one signal to vary a. If poss explain me the working of each syntax in the program. In part three of this lab the fm signal is frequency tripled which also triples the phase deviation or depth of modulation of the fm signal. Your notebook will be checked each week for adequate progress during the course. Frequency modulation, phase modulation, and fm spectra. Emphasis is placed on explaining the tradeoffs that are made to optimize efficiencies in. Amplitude modulation is defined as a process in which the amplitude of the carrier wave ct varied linearly. The lab a measuring of the modulation depth via oscilloscope first part of the lab was to measure the depth of standard amplitude modulation using the spectrum analyser at different amplitudes of the modulating signal. What is fm, frequency modulation electronics notes. Analog modulation an introduction to rf signal, noise and. Modified frequency modulation mfm is a runlength limited rll coding scheme used to encode the actual databits on most floppy disks.
Iict, buet amplitude shift keying ask only amplitude is varied to represent binary 1 or 0. Frequency modulation, fm, variation of the frequency of a carrier wave in accordance with the characteristics of a signal. The objective of this lab is to get familiarized with pulse code modulation. In your lab write up compare this with what is expected for a modulation depth of m 1. It was first introduced in hard disk drives in 1970 with the ibm 3330 and then in floppy disk drives beginning with the ibm 53fd in 1976 mfm is a modification to the original digital frequency modulation also known as fm encoding, delay coding and miller. Is the signal modulated when it transmits through a baseband communication system. In amplitude modulation, the amplitude of the carrier wave is made to vary in accordance with the message signal. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. O, bangalore562110 advanced communication manual 10ecl67 department of electronics and communication engineering prepared by.
Quadrature shift modulation all a,f,p changes combined. The modulating signal sampled, as in other forms of pulse modulation. Each symbol represents n bits, and has m signal states, where m 2n. Suppose there is a nonmodulated carrier at the input. It is also possible to change the frequency of a signal to give frequency modulation or fm.
The amplitude modulation receiver will be wider when compared to the fm receiver. This results in oscillations similar to those illustrated in view b. Frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt. Modulation modulation is the process whereby some characteristic of one wave is v aried in accordance with some characteristic of another wave. Explain the advantages and disadvantages of the different analog modulation techniques. Frequency modulation is widely used on frequencies above 30 mhz, and it is particularly well known for its use for vhf fm broadcasting. This lab is intended to be a beginning tutorial on analog modulation. As explained last month, audio frequency modulation of the amplitude of a signal can be a powerful synthesis tool.
To perform the frequency modulation and demodulation using fm kit. The depth of modulation can be varied using the variable knob provided at a. The fmmodulated signal has its instantaneous frequency that varies linearly with the amplitude of the message signal. It was first introduced in hard disk drives in 1970 with the ibm 3330 and then in floppy disk drives beginning with the ibm 53fd in 1976. Pulse code modulation pcm is a method of converting an analog signal into a digital signal ad. Frequency modulation is a process of changing the frequency of a carrier wave in accordance with the slowly varying base band signal. The sinewave modulated am signal has only three spectral components, at the frequencies,, and. 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 percentage modulation can be calculated using the formula. While changing the amplitude of a radio signal is the most obvious method to modulate it, it is by no means the only way. Switch on the trainer kit and check the op of the carrier generator on oscilloscope. Next month, well take a closer look at some practical aspects of frequency modulation, and introduce the idea of operators a common.
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 and demodulation file exchange. 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. Phase modulation pm amount of phase change on angle of carrier is proportional to intelligence amplitude frequency modulation fm frequency change on angle. Frequency modulation fm is the standard technique for highfidelity communications as is evident in the received signals of the fm band 88108 mhz vs. Frequency modulation objectives upon completion of this chapter, the student should be able to. The move to digital modulation provides more information capacity, compatibility with digital data services, higher data security, better quality communications, and quicker system availability. Electrochemical frequency modulation efm technique. Prof mist mist, hyderabad ece department page 8 physitechs modulation and demodulation trainer has a carrier generator, which generates carrier wave of 100khz when the trainer is switched on. So scroll above and download analog communications lab manual and if you face any problem, dont hesitate to write about it to us.
Note that the fmmodulation is implemented by controlling the instantaneous frequency of a voltagecontrolled oscillatorvco. Digital modulation in communications systems an introduction. The purpose of this lab is to explore digital communications with a software radio to understand how each component works together. Depth of amplitude modulation m when you have completed the previous work you will be displaying a picture like that of e in table 1. This is an important concept in communication systems and, as we will see in lecture 15, also provides the basis for converting between continuoustime and discretetime signals. Amplitude modulation is one of the earliest radio modulation techniques. Calculate the maxima and minima points of modulated wave on the cro and calculate thedepth of modulation using. You will be working in groups of 2 at the lab stations, but each student will maintain a standard laboratory notebook into which all calculations. Modulation summary l phase shift keying is often used, as it provides a highly bandwidth efficient modulation scheme. Frequency modulation software free download frequency. Therefore we only consider the case where the message signal mtis a sinusoidal signal. Where emax and emin are the maximum and minimum amplitudes of the modulated wave. The possibilities expand still further when we consider what happens when you use one audio frequency signal to modulate the frequency of another. Because, atmospheric propagation is good for amplitude modulated signals.
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. To study sample and hold circuit made using op amp. Hence, the pm modulated signal is equal to mp tacos. Set g so that the sinewave peaks just fall to zero.
Prelab theory a frequency modulation fm waveform can be represented mathematically by. Nov 11, 2016 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. Cme312 lab manual frequency modulation experiment 8. Pdf electrochemical frequency modulation efm technique. Power content of frequency modulation and phase modulation. T12 measure the peaktopeak amplitude of the am signal, with m 1, and confirm that this magnitude is as predicted, knowing the signal levels into the multiplier, and its k factor. The number of times per second that the instantaneous frequency is varied from the average carrier. Connect the cro probe to the output of modulation kit and see the wave forms for the modulated signal.
In frequency modulation, the amplitude of the carrier wave is kept constant but its frequency is varied in accordance with the amplitude of the audio frequency signal. Frequency modulation software free download frequency modulation top 4 download offers free software downloads for windows, mac, ios and android computers and mobile devices. 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. We therefore assume mta mcos2 f mtfor pm and mta msim2 f mtfor fm. The fm wave has spectral components at all the frequencies, where n can be any integer from to. Discuss the differences between am and angle modulation. The block diagram of a phase locked loop pll is shown in figure 1.
The lab will cover, analog to digital conversion, modulation, pulse shaping, and noise analysis 1. This is described as a 100% amplitude modulated signal. The value of freqdev must satisfy freqdev lab stations, but each student will maintain a standard laboratory notebook into which all calculations, measurements, prelabs, answers to questions, etc. Peak amplitude during each bit duration is constant. Weexpresstheresultinganglewe express the resulting anglemodulatedwaveasmodulated wave as 4. 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. Calculate modulation index, signal bandwidth, sideband frequencies and. Familiarize yourself with the special modules by reading their descriptions in the posted module handbooks. Bandwidths limit is also big advantage for amplitude modulation, which doesnt have in frequency modulation. In pulse code modulation pcm only certain discrete values are allowed for the modulating signals. Advanced communication lab 2010 department of electronics and communication,msec page 1 m s engineering college iso 90012002, affiliated to vtu, belgaum international airport road,navarathaagrahara, sadahlli p. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is sinusoidal. The receivers used to listen to amdsbc are perhaps the simplest receivers of any radio modulation technique. The following table shows the measured values for different modulation depths.
If the vco was tuned precisely to the frequency of the incoming carrier. Pdf determining instantaneous corrosion rate and corrosion. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value. As mentioned earlier, the amplitude is kept constant. Analog modulation an introduction to rf signal, noise and distortion measurements in the frequency domain by. For fm and pm, the modulating signals are defined by and, respectively, where is the signal frequency in hz, and is its amplitude. Note that the fm modulation is implemented by controlling the instantaneous frequency of a voltagecontrolled oscillatorvco. Vary the modulating frequency and amplitude and observe the effects on the modulated waveform. Apparatus required op amp 1ic 741,capacitor 116pfresistor210 k function generator1for inputcro1for outputemosfet 1n channelconnecting wires theory signal can be defined as a single value. Developers of communications systems face these constraints. Frequency modulation fm the process of combining the message signal with the carrier signal that causes the message signal to vary the frequency of the carrier signal.
The amplitude of the input signal controls the oscillation frequency of the vco output signal. Angle modulation modulation where the angle of a sinewave carrier is varied as a function of the intelligence amplitude. Amplitude shift keying frequency shift keying phase shift keying. For now, on this particular page, we have provided ac lab manual in pdf for jntuh jntuk or jntua students of b. The title of the experiment should be written in the page in capital letters. The maximum deviation of fc which represents the max. If the received carrier phase is assumed to be constant, each of the seven reference values will have to be shifted only once at the beginning of the simulation.
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