It is a nonlinear process that generates additional frequencies, as we will see. In addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well. Angle modulation frequency and phase modulation encode information in the temporal characteristics of the transmitted signal, and consequently they are robust against amplitude noise and. Demodulation of ssb waves, vestigial side band modulation. Amplitude shift keying, quadrature amplitude modulation, inphase component. The process that transforms a message signal into an angle modulated signal is a nonlinear one. This ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. Vsb modulation with envelope detection is used to modulate image in analog tv signals. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted. Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. For angle modulation, the modulated carrier is represented by.
Modulation plays vital role in the field of communication. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. We see that the amplitude spectrum is symmetrical about f c. The amplitude modulation receiver will be wider when compared to the fm receiver. In this video, i have explained amplitude modulation by following outlines. Modulation is a process by which some characteristics of high frequency carrier signal is varied in accordance with the instantaneous value of the modulating signal. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Farshad lahouti january 20, 2003 winter 2003 uw, ece 318 lecture notes 2 information source signal modulator propagation channel signal demodulator information destination analog communication system analog signals may be transmitted directly via carrier modulat ion over. The information is considered as the modulating signal and it is superimposed on the carrier wave by applying both of them to the. The standard equation of the angle modulated wave is in amplitude modulation, the. Uniti amplitude modulation 2 marks questions and answers. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Once a signal has been modulated, information is retrieved through a demodulation process.
The amplitude of the carrier is maintained constant. Download ac unit 3 unit iv angle modulation concepts. Angle cw modulation with noise in the analysis of pm and fm systems, demodulation will be represented by yt. Amplitude modulation of a sine or cosine carrier results in a variation of the carrier am plitude that is proportional to the. Amplitude modulation is a very basic form of modulation, and although its simplicity is one of its major advantages, other more sophisticated systems provide a number of advantages. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Amplitude modulation and demodulation 2017 frank dorenberg n4spp v1. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast.
Radio systems can use a digital signal processor in conjunction with an analogtodigital converter to apply mathematical analysis to iq waveforms. Demodulation, single sideband suppressed carrier ssbsc, double sideband. Phase noise and am noise measurements in the frequency. 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. The method of varying amplitude of a highfrequency carrier wave in accordance with the information to be transmitted, keeping the frequency and phase of the carrier wave unchanged is called amplitude modulation. Frequency modulation and phase modulation are also obtained in a similar way. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam to design the simulink model of the dsbam to analyze each signal in time and frequency domains using time scope and spectrum analyzer. Frequency and phase, or angle, modulation systems on the other hand are nonlinear. In general, amplitude modulation definition is given as a type of modulation where the amplitude of the carrier wave is varied in some proportion with respect to the modulating data or the signal. Vsb signals are generated using standard am or dsbsc modulation, then passing modulated signal through a sideband shaping. Modulationtypesamplitude,frequency,phase modulation. Modulation is a technique to transmit information via radio carrier waveform. Transmitter and receiver are simple in amplitude modulation. Comparing and contrasting amplitude, frequency, and phase.
The separation ofthe am and fm components are illustrated as a modulation phenomenon in fig. A diode is the most widely used device for demodulation. Because, atmospheric propagation is good for amplitude modulated signals. The angle modulation is classified as frequency modulation and phase modulation. The predetection part of an angle modulation receiver is the same as for amplitude modulation. Frequency description, generation of vsb modulated wave, time domain description, envelope detection of a vsb wave pulse carrier, comparison of am techniques, applications of different am systems. This is further divided into frequency and phase modulation. Amplitude modulation am is an analog and linear modulation process as opposed to frequency modulation fm and phase modulation pm. For example, if amplitude of the carrier is chosen to vary in accordance with the instantaneous amplitude of the baseband signal, keeping frequency and phase constant, the resulting modulation called amplitude modulation. Amplitude modulation 2 marks questions and answers 1. It is a nonlinear process that generates additional frequencies, as we. Multiple choice questions and answers on amplitude modulation. Multiple choice questions and answers on modulation and. 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.
Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. The reason is that an lti system preserves the sinusoids. Amplitude modulation am, angle modulation, radio and television. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Amplitude modulation and demodulation nonstop systems. This principle is at the heart of amplitude modulation. This rule is a useful guide when we have to choose a system to carry an fm signal. Pdf analog communication system pdf notes ac notes sw. An am wave may thus be dscribed, in the most general form, as a function of time.
Amplitude fluctuations can be measured with a simple detector such as. Jan 09, 2020 multiple choice questions and answers on amplitude modulation. The reverse of modulation is called demodulation or detection. Quadrature demodulation can extract angle information that is relevant to both frequency modulation and phase modulation. This makes analysis of these signals more difficult. Amplitude modulation electronic engineering mcq questions. Principles of communication modulation tutorialspoint. Modulation allows for the designated frequency bands with the carrier frequency at the center of the band to be utilized for communication and allows for signal multiplexing. The relative amplitudes of the spectral lines depend on the value of jn.
Demodulation of an fm signal requires a system that produces an output proportional. The other type of modulation in continuouswave modulation is angle modulation. In frequency modulation, the frequency of carrier signal is altered in accordance with the the message or transmitting signal. Sep 30, 2017 this ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. In the continuouswave modulation, a high frequency sine wave is used as a carrier wave. Demodulation is a process which extracts the message signal from the modulated signal. Quadrature frequency and phase demodulation radio frequency. Angle modulation is the process in which the frequency or the phase of the carrier signal varies according to the message signal. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that. 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. In this article, you will find the study notes on types of modulation and demodulation which will cover the topics such as introduction to communication systems, amplitude and demodulation, classification of am, angle modulation and demodulation, generation of fm and pulse modulation.
If the amplitude of the high frequency carrier wave is varied in accordance with the instantaneous amplitude of the modulating signal, then such a technique is called as amplitude modulation. Accordingly it is worth looking at some of the disadvantages of amplitude modulation. Angle modulation is a class of carrier modulation that is used in telecommunications transmission systems. Mar 16, 2019 multiple choice questions and answers on modulation and demodulation. Communication involves the transmission, reception and processing of information by electrical means. Amplitude modulation consists encoding information onto a carrier signal by varying the amplitude of the carrier. Bruce carlson, communication systems, an introduction to signals and noise in. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. Amplitude modulation is said to be linear modulation, because as a system it behaves like a linear system. Amplitude modulation is a system of modulation in which the amplitude of the.
The other type of modulation in continuouswave modulation is the angle modulation. Frequency modulation and phase modulation are closely related. In angle modulation, the amplitude of the modulated signal remains fixed while the information is carried by the angle of the carrier. 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. Amplitude modulation an overview sciencedirect topics. The frequency modulation is also classified as narrow band width frequency modulation and wide band width frequency modulation. This is further divided into amplitude and angle modulation. Pdf modulation is an integral part of every modern communication systems. Jun 17, 2018 in this video, i have explained amplitude modulation by following outlines. 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. Amplitude modulation definition, types, solved examples. In linear modulation the amplitude of the carrier signal is a. Analog communication angle modulation tutorialspoint.
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