Amplitude limiters, are used to keep the output constant despite changes in the input signal to remove distortion. An introduction to analog and digital communications, 2nd. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. For a phase modulator, the instantaneous value of the phase angle is equal to phase of an unmodulated carrier plus a time varying component proportional to modulation signal mt. Modulation plays vital role in the field of communication. Angle modulation, ii lecture topics fm bandwidth and carsons rule. Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal. Angle modulation has several advantages over am, such as noise reduction, improved system fidelity and more efficient use of power. Angle modulation frequency modulation consider again the general carrier vc t vc cos. Both frequency modulation and phase modulation fall under the general category of angle modulation.
A broadcast am transmitter radiates 50 kw of carrier power what. Angle modulation 2 1 free download as powerpoint presentation. The class comprises frequency modulation fm and phase modulation pm, and is respectively based on altering the frequency or the phase of. In either case, the frequency of the modulated signal changes as a function of. Slide 3 discretetime fm modulator slide 4 single tone fm modulation slide 5 single tone fm cont. This is additionally separated into frequency and phase modulation.
Communication theory angle modulation important short questions and answers. The class comprises frequency modulation fm and phase modulation pm, and is based on altering the frequency or the phase, respectively, of a carrier signal to encode the message signal. If the modulating signal frequency is changed to khz, with 2 v amplitude, determine the bandwidth of this signal. In this video, i have explained amplitude modulation examples by following outlines. Jun 30, 2018 in this video, i have explained angle modulation by following outlines.
Frequency modulation is the process of varying the frequency of the carrier signal linearly with the message signal. Basic concepts of modulation three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. But in frequency modulation the instantaneous angular frequency i varies linearly with the modulating signal mt, tt t k m d t k m d c f c f then fm and pm are very much related to each other. Begin by writing an angle modulated signal in complex form xc. Angle modulation in principles of communication tutorial. Angle modulation is further divided into frequency modulation and phase modulation. Modulation techniques for mobile radio school of information science and engineering, sdu. The modulation processisprobablyeasier tounderstand whenviewed fromthe perspective of amplitude modulation. Angle cw modulation with noise in the analysis of pm and fm systems, demodulation will be represented by yt. Phase modulation in this type of angle modulation, the phase angle t is varied linearly with a modulating signal ft about an unmodulated phase angle ct. Besides using the amplitude of a carrier to carrier information, one can also use the angle of a carrier to carrier information. A step angle change is a step phase change of the carrier.
Properties of angle modulation university of toronto. In this video, i have explained angle modulation by following outlines. The predetection part of an angle modulation receiver is the same as for amplitude modulation. Angle modulation is capable of handling a greater dynamic range in the modulating signal without distortion as would occur in am. Angle modulation suppose that f m d1khz and f d d2. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. May 28, 2017 pulse modulation techniques pam, pwm, ppm, pcmpulse amplitude,pulse width,pulse position, code duration. That is to say, the instantaneous value of a phase angle i is equal to the phase of an unmodulated carrier ct plus a time varying component proportional to ft. Unlike am there is no single theory that can handle the general pm and fm cases. Suppose that the input narrowband fm signal has a frequency deviation of 2. The amplitude of the carrier is maintained constant. Frequency and phase modulation are together named as angle modulation.
Analog communication angle modulation tutorialspoint. Bandwidthexpansion of angle modulation effective bandwidth. Anglemodulation,ii lecturetopics fmbandwidthandcarson. Question about fm and pm and angle modulation electrical. Phase modulation is similar to frequency modulation and is an important technique in digital communication systems. But phase modulation seems to be in a different categorypm radio is by no means a common term. Angle modulation allows for more efficient use of transmitter power. Each unique message signal has a different assigned carrier frequency e. Angle modulation is the procedure in which the frequency or the phase of the carrier differs according to the message signal. An important feature of angle modulation is that it can provide better. For example, with one bit, only 2 1 2 conditions are possible. However, angle modulation also has several disadvantages when compared to am, including requiring a wider bandwidth and utilizing more complex circuits.
When the modulation index is less than 1, the angle modulated systems are called low index. Angle modulation is very efficient in rejecting interference i. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. Angle modulation introduction there are three parameters of a carrier that may carry information. The pm and fm of the example are shown here for a c. In our previous articles, we have discussed the various types of amplitude modulation systems in which the carrier amplitude is changed in accordance with the variation in the message signal magnitude. Angle modulation is a class of carrier modulation that is used in telecommunications transmission systems. Amplitude modulation an overview sciencedirect topics. There are two common forms of angle modulation, namely, phase modulation and frequency modulation. The angle modulation is classified as frequency modulation and phase modulation. Think of this angle as the angle of a phasor rotating at a constant angular velocity. Lecture 12 angle modulation elg3175 introduction to communication systems.
For the example above, the carrier signal is p es cos2. Phase and frequency modulation think about what it means to modulate the phase of a cosine. With two bits, 2 2 4 conditions are possible, with three bits, 2 3 8 conditions are possible, and so on. There are two ways of varying the angle of the carrier. Amplitude frequency phase frequency and phase modulation are closely related and grouped together as phase modulation frequency modulation power in an fm signal does not vary with modulation fm signals do not have an envelope that reproduces the modulation the figure below shows a. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Angle modulation 1 frequency modulation modulation. Angle modulation 2 1 frequency modulation modulation. Angle modulation is nonlinear and complex to analyze.
Its primary purpose is to map the information sequence into. Illustration of frequency deviation diksha prakash. In practice, this modulation will not be perfect, and there will be some amplitude modulation remaining. In this modulation, the amplitude of the carrier signal varies in accordance with the message signal, and other factors like phase and frequency remain constant. The interest in angle modulation is due to the decreasing effect of noise or interferences on it, when compared with am, although at the cost of a much wider bandwidth and greater complexity in implementation. This approach is called angle modulation, and includes frequency modulation fm and phase modulation pm. Angle modulation the modulation which is based on changing the frequency or phase of the carrier signal with respect to message signal is called angle modulation. Frequencyshiftkeyingfsk the binary message can be detected using two. Similarly, the narrowband approximation for phase modulation is.
Ee4512 analog and digital communications chapter 6 the instantaneous phase the the. The minimum sampling rate nyquist rate 10k samplessec. The bandwidth requirement of low index systems is approximately twice of the modulating. However, their modulation and demodulation are rather simple to implement.
Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. There are lots of other circuits that have been invented for fm modulation. Outline l frequency versus amplitude modulation l amplitude modulation am l angle modulation ldigital modulation l line coding l pulse shaping techniques l geometric representation of modulation signal. Professor deepa kundur university of torontoproperties of angle modulation 25 4. In phase modulation pm the instantaneous angular frequency. This approach is called angle modulation, and includes frequency modulation. Immunity of angle modulation to nonlinearities very useful feature of angle modulation is its constant amplitude, which makes it less susceptible to nonlinearities amplifier with second order nonlinear distortion clearly, the first term is the desired signal amplification term, the remaining terms are the unwanted nonlinear distortion. The angle contains harmonic distortion in the form of third and higher order harmonics of the modulation frequency it f m. The nonlinear behavior of angle modulation systems makes their analysis more difficult than that for am. Frequency modulation is the procedure of changing the frequency of the. Angle modulation from the book electronic communication systems by roy blake. After the step change the carrier frequency remains as it.
Phase modulation is the process of varying the phase of the carrier signal linearly with the message signal. Frequency modulation is a special case of angle modulation where the instantaneous frequency of a carrier is varied by an amount proportional to the modulating signal amplitude. Frequency modulation examples, fm examples in analog. Ee4512 analog and digital communications chapter 6. Frequency modulation negative deviation positive deviation figure. Apr 10, 2016 frequency modulation it is a type of angle modulation in which the instantaneous frequency varied linearly in accordance to baseband or modulating signal. The other type of modulation in continuouswave modulation is angle modulation.
Angle modulation article about angle modulation by the free. Angle modulation is the process in which the frequency or the phase of the carrier signal varies according to the message signal. This makes analysis of these signals more difficult. The envelope contains a residual amplitude modulation that varies with time the angle contains harmonic distortion in the form of third. The modulation which is based on changing the frequency or phase of the carrier signal with respect to message signal is called angle modulation. In angle modulation, the amplitude of the modulated signal remains fixed while the information is carried by the angle of the carrier. This type of modulation technique is used in electronic communication.
Introduction to analog and digital communications second edition simon haykin mcmaster university, hamilton, ontario, canada. After the step change the carrier frequency remains as it was before the change. Mar 27, 2020 this is the multiple choice questions in chapter 4. The continuous analog signal st is a baseband signal with the information content. In fm the angle is directly proportional to the integral of mt, i. Chapter 6modulation techniques shandong university. Pdf analog communication system pdf notes ac notes sw. Communication involves the transmission, reception and processing of information by electrical means. As in other modulation systems, the value of the modulation index indicates by how much the modulated variable varies around its unmodulated level. A continuous, progressive, linear angle change to the carriers phase equates to a fixed frequency displacement of the carrier. Angle modulation is resistant to propagationinduced selective fading because amplitude variations are unimportant. Slide 6 narrow band fm slide 7 bandwidth of an fm signal slide 8 demod. The process that transforms a message signal into an angle modulated signal is a nonlinear one. The standard equation of the angle modulated wave is in amplitude modulation, the.
A 1 mhz carrier of 10 v amplitude, when frequency modulated by a 400 hz 1 volt modulating signal, undergoes 1 khz deviation. Frequency modulation it is a type of angle modulation in which the instantaneous frequency varied linearly in accordance to baseband or modulating signal. The other type of modulation in continuouswave modulation is the angle modulation. From my standpoint, angle modulation can be fm or pm. This is the multiple choice questions in chapter 4. Angle modulation is the modulation in which phase or frequency of the carrier signal is varied with respect to message or transmitting signal.
Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. Introduction to angle modulation in angle modulation, the amplitude of the modulated signal remains fixed while the information is carried by the angle of the carrier. Example commercial fm signals use a peak frequency deviation of. Angle modulation langle of the carrier is varied according to the amplitude of the modulating baseband signal.