This text then examines all the general problems of frequency modulation, including principle, band covered, distortion, and improvement of the signaltonoise ratio. Am radio is on a lower frequency, so it travels further. Explain the advantages and disadvantages of the different analog modulation techniques. The frequency components present in the am wave are represented by vertical lines approximately located along the frequency axis. The subject is new and all of its ramifications and prob lems are not known as yet, hence this volume of compara tively few pages is not intended as a complete exposition of the subject. Frequency modulation is used in different applications like radar, radio and telemetry, seismic prospecting and monitoring newborns for seizures via eeg, etc. In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Frequency modulation simple english wikipedia, the free. What is the difference between phase modulation and. Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal. 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. In this chapter, let us solve a few problems based on the concept of frequency modulation. All about modulation basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk.
It has been proposed that the detection of frequency modulation fm of sinusoidal carriers can be mediated by two mechanisms. In frequency modulation fm, unlike am, the amplitude of the carrier is kept constant, but its frequency is altered in accordance with variations in the audio signal being sent. Modulation is the process of superimposing a low frequency signal on a high frequency carrier signal. To generate a frequency modulated signal, the frequency of the radio carrier is changed in line with the amplitude of the incoming audio signal. Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase. The term and technology us 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. This form of modulation was developed by the american electrical engineer edwin h. Read about the many types of radio frequency modulation radio frequency modulation in our free electronics textbook. Principles of communication modulation tutorialspoint. 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.
Angle modulation all 0 free download as powerpoint presentation. Its nothing to do with the fm modulation, its to do with the higher frequency used for fm radio broadcasts, compared with am radio broadcasts. It is also the basis of the first commercially successful method for digital sound synthesis. Pdf detection of frequency modulation by hearingimpaired. In this book, only phase modulation will be considered, and we will call it fm, following common practice. Or the process of modulation can be defined as varying the rf carrier wave in accordance with the intelligence or information in a low frequency signal.
Potential confusion aside, any modulation of phase implies a modulation of frequency, and vice versa, since the instantaneous frequency is always defined as the timederivative of the instantaneous phase. The other type of modulation in continuouswave modulation is the angle modulation. Frequency modulation is widely used on frequencies above 30 mhz, and it is particularly well known for its use for vhf fm broadcasting. Frequency modulation and its application slideshare.
Modulation index of an fm wave the modulation index is the ratio of the amount of frequency deviation to the audio modulating frequency. Fir these stations the maximum frequency deviation is 75 khz, and the maximum audio frequency fort he modulation is 15 khz. Amplitude modulation frequency spectrum frequency spectrum of am wave. Three kinds of modulations modulation is the process of facilitating the transfer of information over a medium.
Modulation is the process of changing the parameters of the carrier signal, in accordance with the instantaneous values of the modulating signal. Hence info is carried in the phase or frequency of the carrier. Frequency versus amplitude modulation l frequency modulation fm l most popular analog modulation technique l amplitude of the carrier signal is kept constant constant envelope signal, the frequency of carrier is changed according to the amplitude of the modulating message signal. In fm, the rf is deviated from its original frequency. Transmission rate is good for frequency modulation when compared to other modulation that is frequency modulation can transmit around 1200 to 2400 bits per second.
In this type of modulation, the frequency of the carrier signal varies in accordance with the message signal, and other parameters like amplitude and phase remain constant. One approach to reduce this interference, known as. Radio frequency modulation made easy popular electronics. What is the difference between phase modulation and frequency. As shown in the figure, modulation is performed at the transmit side and demodulation is performed at. Frequency versus amplitude modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal. The baseband signals are incompatible for direct transmission. Modulationtypesamplitude,frequency,phase modulation. Frequency modulation has a special effect called capture effect in which high frequency signal will capture the channel and discard the low frequency or weak signals from interference. An important feature of angle modulation is that it can provide better. Frequency modulation is the process in which the frequency of the carrier signal is varied by the modulating signal while the amplitude remains constant. The signals that represent useful information are difficult to transmitpropagate. Amplitude modulation am frequency modulation fm phase modulation pm click on the links given above to know more. While changing the amplitude of a radio signal is the most obvious method to modulate it, it is by no means the only way.
I mean, i am not playing wav file, and i cannot just speed up its playback. Frequency modulation is a form of modulation, which represents information as variations in the instantaneous frequency of a carrier wave. Fm modulated signal st is a nonlinear function of the modulating signal mt, thus it is known as nonlinear modulation process. The many types of radio frequency modulation radio. In telecommunications and signal processing, frequency modulation transmits information over a carrier wave by varying the frequency. In fm, the frequency changes but the amplitude remains unchanged. Calculate the frequency deviation, modulation index, and bandwidth. But phase modulation seems to be in a different categorypm radio is by no means a common term. Invented by john chowning, it was the method used in the the highly successful yamaha dx7 synthesizer, and later the yamaha opl chip series, which. Recall that we can write an equation for a sine wave as follows. Other chapters deal with propagation distortion that is apparent in a variablevelocity guided transmission channel.
The classic definition of fm is that the instantaneous output frequency of a transmitter is varied in accordance with the modulating signal. Introduction manner in which it differs from amplitude modulation, and details associated with f m receiver servicing problems. Frequency modulation definition of frequency modulation. Discuss the differences between am and angle modulation. However if st is sinusoidal, then the instantaneous frequency deviation of the anglemodulated signal is. Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase, of a carrier is varied in accordance with instantaneous value of some other voltage. 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. Modulation, in electronics, technique for impressing information voice, music, picture, or data on a radiofrequency carrier wave by varying one or more characteristics of the wave in accordance with the intelligence signal.
Oct 09, 2014 frequency modulation and its application 1. Calculate modulation index, signal bandwidth, sideband frequencies and. There are various forms of modulation, each designed to alter a. Chapter 6modulation techniques shandong university. Next month, well take a closer look at some practical aspects of frequency modulation, and introduce the idea of operators a common. Modulation techniques pwm and pulse code modulation. To extend the range your voice can reach, we need to. Frequency modulation fm is well known as the broadcast signal format for fm radio. Frequency modulation is used in a variety of applications. Sinusoidal frequency modulation fm mathematics of the dft. Since the three variables are the amplitude, frequency, and phase angle, the modulation can be done by varying any one of them. What is fm, frequency modulation electronics notes. The term and technology us used in both telecommunications and signal processing.
The phasitron system of frequency modulation, which has recently come into practical use, is based on a new tube structure. It is also possible to change the frequency of a signal to give frequency modulation or fm. 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 definition is modulation of the frequency of the carrier wave in accordance with speech or a signal. The amount of frequency deviation in fm depends on the amplitude of the af signal. The process of modulation can be defined as varying the rf carrier wave in accordance with the intelligence or information in a low frequency signal. 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. The spectrum of an fm signal is quite complicated and is dependent on mf. Read about the many types of radio frequency modulation radio frequency modulation. Modulation, in electronics, technique for impressing information voice, music, picture, or data on a radio frequency carrier wave by varying one or more characteristics of the wave in accordance with the intelligence signal. Narrowband frequency modulation narrowband fm means that the fm modulated wave has narrow bandwidth.
The height of each vertical line is drawn in proportion to its. Frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The carrier amplitude is constant and the phase variation of the signal contains the information. Amamplitude modulation fm frequency 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. There are two common forms of angle modulation, namely, phase modulation and frequency modulation. Sound transmission in air has limited range for the amount of power your lungs can generate. Frequency and phase modulation sharlene katz james flynn overview history why fm. A sinusoidal modulating waveform of amplitude 5 v and a frequency of 2 khz is applied to fm generator, which has a frequency sensitivity of 40 hzvolt. The amount of decrease or increase around fc is called the frequency deviation.
All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Modulation is a technique that changes the characteristics of the carrier frequency in accordance to the input signal 1, 2. This is further divided into frequency and phase modulation. This kind of modulation is used in broadcasting and other radio work in the context of broadcasting, frequency modulation is. Aug 28, 2015 transmission rate is good for frequency modulation when compared to other modulation that is frequency modulation can transmit around 1200 to 2400 bits per second. This kind of modulation is used in broadcasting and other radio work.
For such a signal, to travel longer distances, its strength has to be increased by modulating with a high frequency. When the audio signal is modulated onto the radio frequency carrier, the new radio frequency signal moves up and down in frequency. This technique is different from amplitude modulation which varies the amplitude, but keeps the frequency constant. Frequency modulation is the process of varying the frequency of the carrier signal linearly with the message signal. Phase modulation is similar to frequency modulation and is an important technique in digital communication systems. Chapter 2 concerns all the general problems of frequency modulation, while chapter 3 deals with the propagation distortion, which is apparent in a variablevelocity guided transmission channel, and, which appears on an echoing path either in free space, or over a badly matched feeder. Angle modulation all 0 frequency modulation modulation. It is possible that certain human languages are especially effective in conveying certain types of information. Example commercial fm signals use a peak frequency deviation of. Frequency modulation objectives upon completion of this chapter, the student should be able to.
1571 1221 971 316 742 630 745 1298 1177 1007 530 1094 1562 141 877 1526 219 519 1305 221 432 868 1115 951 1564 1397 212 1069 1239 937 151 1403 668 582 904