Xr2212 is a highly stable, monolithic pll phase locked loop ic specifically designed for communication and control system applications. The goal of this experiment is to become familiar with fm modulation and demodulation. Fm modulation and demodulation electrical and computer. Frequency modulation 1 objective to understand the principles of frequency modulation and demodulation. Fm modulated signal st is a nonlinear function of the modulating signal mt, thus it is known as nonlinear modulation process. The typical frequency of the transmitted and received. Frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt.
Mar 31, 2015 high capacity microwave links with 256qam 1024qam 2048qam and 4096qam modulation for gigabit wireless metropolitan area networks and 4glte backhaul. The quadrature detector required the use of very few components, but does require a coil. The main advantage of fm over am is its noise immunity, as limiter stage in fm receiver clips off noise signals. A simple pll fm demodulator circuit using ic xr2212 is shown here. Mar 16, 2019 multiple choice questions and answers on modulation and demodulation in addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well. In addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well. 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. Another property used to compare waves is the frequency of a wave, which is defined as the number of waves created per second. The signal output from a demodulator may represent sound an. Aug 26, 2016 this is because fm waves have a small range in terms of the geographical regions they can cover, whereas am waves have a much larger range and can therefore be received even in hinterlands.
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. Now the mdsr core software can be adapted to all java capable. Modulation, analog modulation, digital modulation, am,fm. Dec 29, 2017 when you modulate a radio carrier wave, you change it you impress a signal on it. Thus, if mt is the message signal and ctacosw c t then fm signal will be. Calculate modulation index, signal bandwidth, sideband frequencies and. Implementation of fm demodulator algorithms on a high performance digital signal processor tms320c6711 dsp franz schnyder christoph haller 11. Radio waves have the longest wavelength compared to other types of waves see figure.
Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. You will model the pll, and recover the message from the fm signal. Fm modulator that was described in a previous lecture. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Waves transfer energy without moving matter, similar to ocean waves or sun light. Thus, as a signal passes from air of one density to that of a different density, the direction of travel is altered. Multiple choice questions and answers on modulation and. The second section will be the design of the fm radio front end. The amplitude of the carrier component of an fm wave is dependent on the modulation index. Refraction refraction of radio waves is similar to that of light waves. Make sure that the triangle and square waves are both antipodal waveforms balanced above and below 0 volts.
Fm stereo is widely used in vehicular transceiver9, mobile communication system10 and so on, and fm stereo receiving is often used in broadband wireless receiver, so the paper research fm stereo receiver based on software defined radio. Frequency modulation objectives upon completion of this chapter, the student should be able to. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Modulation is a data transmission technique that transmits a message signal inside another higher frequency carrier by altering the carrier to look more like the message.
In general in air, electromagnetic waves such as radio signals travel longer than mechanical waves such as sound. Angle modulation, ii lecture topics fm bandwidth and carsons rule. Fm demodulation is also called fm detection and sometimes the phrase fm discrimination is used, although this term tends to be used with older circuits and technology. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. For frequency modulation, going past the designed deviation value will produce a signal whose bandwidth exceeds that for which the receiver was designed. Remember to set up the vco module in 100 khz vco mode. The fm wave is effectively composed of a carrier and a single pair of sidefrequencies at. To improve the quality of reception to increase the range of communication need of demodulation the wireless signal consists of radio frequency high frequency carrier wave modulated by audio frequency low frequency. The average power of an fm wave may also be determined from.
Frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. Chapter 8 frequency modulation fm contents umd ece. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. Describe fm demodulation circuit operation for the phaseshift and gatedbeam. The lm 566 delivers either an fm square wave or an fm triangular wave. Fm wave does not look at all like the modulating waveform. Sep 20, 2012 frequency modulation frequency modulation is the process by which frequency of the carrier signal ct changes with respect to the modulating signal mt. John chowning tells me that he stumbled on fm when he sped up vibrato to the point that it was creating audible sidebands perceived as a timbral change rather than faster warbling.
It received a totally new dsp engine to upgrade to the jsyn 100% java sound synthesizer. As the waves propagate away from the source, the frequency also represents the number of waves that will pass a point per second. The modulation depth am or frequency deviation fm is controlled by the signal level on the rearpanel modulation in connector. Continuouswave cw modulation consists of onoff keying of a carrier wave. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Lexapro stopped my panic attacks and anxiety attacks within a couple of days. 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. Fm demodulation is a key process in the reception of a frequency modulated signal. Amplitude modulation am and frequency modulation fm. A demodulator is an electronic circuit or computer program in a softwaredefined radio that is used to recover the information content from the modulated carrier wave. The fm quadrature demodulator and its relation the coincidence detector or demodulator provide another form of fm detector circuit that is used in many areas, being easily incorporated into integrated circuits.
All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. The fm output for a square wave looks like frequency shift keying fsk. Frequency modulation fm is the standard technique for highfidelity communications as is evident in the received signals of the fm band 88108 mhz vs. The averate power of such as signal developed across a 1ohm resistor is also constant. In this method of modulation the amplitude of the carrier wave is maintained constant. There are different types of modulation and so are demodulators. If this input signal is added to the pure carrier wave, it will thereby change the frequency of the carrier wave. Early developers thought that bandwidth could be reduced to 0. The main reason for the improved fidelity is that fm detectors, when properly designed, are not sensitive to random amplitude variations which are the.
December 26, 2018 waveofmodulation leave a comment. This is the reason most news stations use am over fm, because they want the information to reach as many people as possible, even if the sound quality isn. Angle modulation is nonlinear and complex to analyze. The aim of this topic is to explore the reasons for using modulation. The generated narrowband fm signal can be converted to a wideband fm signal by simply passing it through a nonlinear device with. The receiver will experience distortion because part of the signal has been filtered out, and the excessive bandwidth of the transmitted signal may interfere with stations on adjacent frequencies. The narrowband fm modulator generates a narrowband fm signal using simple components such as an integrator an opamp, oscillators, multipliers, and adders. The bandwidth of an fm signal is proportional to the modulation index. In that way, users can use changes of frequency to carry speech information. Abstract analog modulations are more and more replaced by digital ones. Fm or frequency modulation is the process of varying the in instantaneous frequency of carrier signal accordingly with instantaneous amplitude of message signal. Two signals are involved in the modulation process.
A history, and communication, amplitude modification am and frequency modulation fm edited by jamie scienceaid editor, taylor scienceaid. Intrawave frequency modulation and nonlinear distortion degree in the hht principle, the. There are many types of modulation so there are many types of demodulators. However, this is not important, since the squaretriangular wave can be converted into a good sinewave with the use of a simple rc filter. Multiple choice questions and answers on modulation and demodulation.
The phase of the carrier wave is also kept constant. Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission than frequency shift keying, a form of frequency modulation. Explain the advantages and disadvantages of the different analog modulation techniques. The term and technology is used in both telecommunications and signal processing 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. When you modulate a radio carrier wave, you change it you impress a signal on it. Recall that we can write an equation for a sine wave as follows. For example, the signal in a cell phone is a voice signal with a bandwidth of about 4 khz. The design approach is to design the fm demodulator as if it were an analog phase lock loop. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors.
The fmmodulated signal has its instantaneous frequency that varies linearly with the amplitude of the message signal. The bad news is that, in practice we often have to know in advance which type of modulation is being used if we want to recover the modulated information correctly. Once the signal has been received, filtered and amplified, it is necessary to recover the. These two strategies can be combined to create a third scheme. A history, and communication, amplitude modification am and frequency modulation fm edited by jamie scienceaid editor, taylor scienceaid editor, maniwanttodie24, jen moreau and 2 others. Since a frequencymodulated wave has constant amplitude, it is possible to have two frequencymodulated waves that are nearly equal in amplitude all of the time. Implementation of fm demodulator algorithms on a high. Frequency modulation, phase modulation, and fm spectra. Pdf on amplitude and frequency demodulation using energy. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i.
Other articles where modulation of waves is discussed. The external modulation input has 3 db bandwidth of 100 khz. The input impedance for the modulation signal is 1 m. Demodulation is extracting the original informationbearing signal from a carrier wave. The term and technology is used in both telecommunications and signal processing. The classic definition of fm is that the instantaneous output frequency of a transmitter is varied in accordance with the modulating signal. This can be voice or other sounds, pictures, think tv, or other information. Modulation, analog modulation, digital modulation, am,fm,pm. Discuss the differences between am and angle modulation. The instantaneous frequency of an fm wave with carrier frequency. Quadrature amplitude modulation qam is a form of modulation that uses two carriersoffset in phase by 90 degreesand. The phase angle associated with the fm signal is given by.
Its amplitude a, which leads us to the class of systems designated as amplitude. Modulation and demodulation techniques request pdf. Modulation is defined as a process by virtue of which, some characteristic of a high frequency sinusoidal wave is varied in accordance with the instantaneous amplitude of the baseband signal. In frequency modulation we modulate the frequency modulation here is just a latinate word for change. Oct 08, 2017 waves transfer energy without moving matter, similar to ocean waves or sun light. For fm, the % of modulation is the ratio of the actual frequency deviation and the maximum permissible frequency deviation multiplied by 100.
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