Pdf on amplitude and frequency demodulation using energy. Pll and frequency demodulation 3 when signals have different values, we should change frequency of the vco. If the signal is frequency modulated, as shown i n figure 2, the spectral line will correspondingl y shift in the frequency domain. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. 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. The averate power of such as signal developed across a 1ohm resistor is also constant. Fm modulated signal st is a nonlinear function of the modulating signal mt, thus it is known as nonlinear modulation process. Switch off the rotation and fm sections by clicking on their onoff controls.
Fm wave does not look at all like the modulating waveform. As mentioned earlier, the amplitude is kept constant. Exercise 51 generating ssb signals by the filter method 91. Capacitor microphone fm generator simplest fm generator transmitter refer to fig 51 next slide lc tank and oscillator generate sinewave output that goes to antenna capacitance on lc tank is a capacitor microphone aka condenser mike frequency of impinging sound waves intelligence determines the rate of output frequency change amplitude of impinging sound waves. In this method of modulation the amplitude of the carrier wave is maintained constant. For example, the signal in a cell phone is a voice signal with a bandwidth of about 4 khz. Abundant modulation function, various modulated waveform. Frequency modulation fm as s hown in figure 1, an unmodulated rf signal in the time domain has only a single spectral line at the carrier frequency f c in the frequency domain. The carrier has three parameters that could be modulated.
Frequency modulation 1 objective to understand the principles of frequency modulation and demodulation. Set the proper amplitude and frequency of the modulating signal to get a reasonable fm waveform. Fm radio the bandwidth of an audio signal speech and music in is almost 15 khz. The vco performs freq modulation on its own control signal vt, so the phase is. Frequency modulation in pm the instantaneous frequency. Its main advantage is that it is more resistant to additive noise than am. 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. Angle modulation consider a modulating signal mt and a carrier vct acos. In general it involves translating a baseband signal source. Notice that the function generator powers up in the sine wave function. Calculate modulation index, signal bandwidth, sideband frequencies and. Among the types of modulation techniques, the main classification is continuous wave modulation and pulse modulation. Discuss the differences between am and angle modulation. 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.
Explain the advantages and disadvantages of the different analog modulation techniques. Orthogonal frequency division modulation 2 ofdm 6 a adjacent subchannels interfere b guard bands protect leakage from adjacent frequencies figure 9. The second section will be the design of the fm radio front end. The average power of an fm wave may also be determined from. Switch off the experimental kit during making connections. Abstract analog modulations are more and more replaced by digital ones. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. However, this is not important, since the squaretriangular wave can be converted into a good sinewave with the use of a simple rc filter. Instantaneous frequency the instantaneousfrequencyof cos. The fmmodulated signal has its instantaneous frequency that varies linearly with the amplitude of the message signal. It requires that the amplitude of the dc a part of at is equal to the amplitude of the ac part a. This results in oscillations similar to those illustrated in view b.
Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. Modified frequency modulation mfm is a runlength limited rll coding scheme used to encode the actual databits on most floppy disks. Three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Always be sure the work cable makes a good electrical connection with the metal being welded. Application note an insight intermodulation distortion measurement methods using the ifr 2026ab multisource generator.
The lm 566 delivers either an fm square wave or an fm triangular wave. The userfriendly panel layout and instructions, versatile terminals, direct. 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. The wave period is inversely proportional to the frequency the longer the period, the lower the frequency.
These ideas are then extended to a more general class of signals that are sine waves with a timevarying amplitude and frequency and thus contain both an am and an fm component. A simple pll fm demodulator circuit using ic xr2212 is shown here. The latter two methods are closely related since both modulate. Narrowband frequency modulation narrowband fm means that the fm modulated wave has narrow bandwidth. Waves and abbey road studios have faithfully recreated the unique magic of the rs56, using advanced circuit modeling techniques based on the original schematics. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Distinguish between different types of fm signal 4. The continuous analog signal st is a baseband signal with the information content. Cme312 lab manual frequency modulation experiment 8. Users guide dg1022 dualchannel arbitrarywaveform generator. By the end of this experiment, the student should be able to.
This means that their ratio is unity at the output of the adder, which forces m to a magnitude of exactly unity. This is the time it takes for the wave to undergo one complete oscillation or one complete motion. The amplitude of the carrier component of an fm wave is dependent on the modulation index. A continuous wave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Now we can hear the effect of amplitude modulation alone.
Idr offers two dither types and three noiseshaping curves to optimize processing of a wide variety of applications and source material. Implementation of fm demodulator algorithms on a high performance digital signal processor tms320c6711 dsp franz schnyder christoph haller 11. Frequency modulation 7 frequency modulation frequency of carrier signal follows changes in voltage level amplitude of modulating signal st a cos2 f t 2 k xtdt a c cosi t t 0 c. Frequency modulation objectives upon completion of this chapter, the student should be able to. The frequency modulated signal can be written as st a ccos 2. Examine the factors affecting the shape of the spectrum and the bandwidth of fm signals. Finally, fmstereo multiplex operation will be introduced as an example of an early form of combinational modulation used to send more. The number of times per second that the instantaneous frequency is varied from the average carrier. A noncoherent detector has only one input, namely, the modulated signal port. Upon completion of the experiment, the student will. The main reason for the improved fidelity is that fm detectors, when properly designed, are not sensitive to random amplitude variations which are the. Modulation is the process of encoding information from a message source in a manner suitable for transmission. Fm modulation and demodulation electrical and computer. Its amplitude a, which leads us to the class of systems designated as amplitude.
Having a choice of components for a particular processor gives you the flexibility to choose the configuration best suited to your material. The fm wave is effectively composed of a carrier and a single pair of sidefrequencies at. By substituting 6 into 2, the key fm expression in 5 is shown to be satis ed. In semiautomatic or automatic wire welding, the electrode, electrode reel, welding head, nozzle or semiautomatic welding gun are also electrically hot. The number of wave crests is reduced for a time at greatest modulation but frequency downshifting is not. The range of wave steepness and modulation lengths that give breaking waves are determined. Implementation of fm demodulator algorithms on a high. Although still widely used, frequency modulation fm synthesizers are most. Properties of angleproperties of anglemodulated wavesmodulated waves property 1. Sound transmission in air has limited range for the amount of power your lungs can generate. Capacitor microphone fm generator simplest fm generator transmitter refer to fig 51 next slide lc tank and oscillator generate sinewave output that goes to antenna capacitance on lc tank is a capacitor microphone aka condenser mike frequency of impinging sound waves intelligence determines the rate of output frequency.
Abbey road rs56 passive eq plugin features three bands with four selectable center. Xr2212 is a highly stable, monolithic pll phase locked loop ic specifically designed for communication and control system applications. Introduction intermodulation distortion imd is a common problem in a variety of areas of electronics. Multiplexingmedium access control 2 digital modulation 3 why modulate. Modulation is the process in which some property of the high frequency wave, also called as carrier wave c, is altered in such way by low frequency information signal, called as. The design approach is to design the fm demodulator as if it were an analog phase lock loop. Frequency modulation fm is the standard technique for highfidelity communications as is evident in the received signals of the fm band 88108 mhz vs. Coded modulation pcm is a form of modulation where there is no carrier, so that makes it a pure digital system. Modulation is the process by which we map information on to a carrier. Chapter 8 frequency modulationfm fm was invented and commercialized after am.
To send these electromagnetic waves across long distances in free space, the frequency of the transmitted signal must be quite high compared to the frequency of the information signal. Lab manual frequency modulation experiment 8 experiment 2 objectives. 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. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt. The goal of this experiment is to become familiar with fm modulation and demodulation. The waves idr process, based on michael gerzons noiseshaping, redithering technique, prevents this loss of critical lowlevel detail. The phase of the carrier wave is also kept constant. To extend the range your voice can reach, we need to transmit it through a medium other than air, such as a phone line or radio. Subcarriers in ofdm it is easy to see that these subcarriers are orthogonal, i. The actual frequency spectrum of a fm signal is challenging to find. The input impedance for the modulation signal is 1 m. There are different types of modulation and so are demodulators.
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