This rule is a useful guide when we have to choose a system to carry an fm signal. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. In the continuouswave modulation, a high frequency sine wave is used as a carrier wave. 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.
Principles of communication modulation tutorialspoint. In angle modulation, the amplitude of the modulated signal remains fixed while the information is carried by the angle of the carrier. Amplitude modulation and demodulation nonstop systems. 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. 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. The reverse of modulation is called demodulation or detection.
Amplitude modulation is said to be linear modulation, because as a system it behaves like a linear system. Amplitude modulation an overview sciencedirect topics. The predetection part of an angle modulation receiver is the same as for amplitude modulation. 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. Pdf modulation is an integral part of every modern communication systems. 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. Amplitude modulation am, angle modulation, radio and television. This principle is at the heart of amplitude modulation. Amplitude modulation consists encoding information onto a carrier signal by varying the amplitude of the carrier. Download ac unit 3 unit iv angle modulation concepts. The other type of modulation in continuouswave modulation is angle modulation. This includes both ordinary analog amplitude modulation and the widely used digital schemes known collectively as quadrature amplitude modulation qam. An am wave may thus be dscribed, in the most general form, as a function of time.
Bruce carlson, communication systems, an introduction to signals and noise in. Each channel sharing scheme a set of basis vectors. 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. 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. Quadrature demodulation can extract angle information that is relevant to both frequency modulation and phase modulation. The information is considered as the modulating signal and it is superimposed on the carrier wave by applying both of them to the. Demodulation of an fm signal requires a system that produces an output proportional. Demodulation is a process which extracts the message signal from the modulated signal. Amplitude modulation electronic engineering mcq questions. In addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well. Multiple choice questions and answers on amplitude modulation. This is further divided into amplitude and angle modulation. 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.
Comparing and contrasting amplitude, frequency, and phase. 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 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. Jan 09, 2020 multiple choice questions and answers on amplitude modulation.
Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal. Demodulation uses either standard am or dsbsc demodulation, depending on whether a carrier tone is transmitted. Amplitude shift keying, quadrature amplitude modulation, inphase component. Because, atmospheric propagation is good for amplitude modulated signals. Mar 16, 2019 multiple choice questions and answers on modulation and demodulation. 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. Amplitude modulation 2 marks questions and answers 1. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier.
In linear modulation the amplitude of the carrier signal is a. Angle modulation is a class of carrier modulation that is used in telecommunications transmission systems. In this video, i have explained amplitude modulation by following outlines. It is a nonlinear process that generates additional frequencies, as we. Once a signal has been modulated, information is retrieved through a demodulation process. This ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. Phase noise and am noise measurements in the frequency.
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. A diode is the most widely used device for demodulation. Uniti amplitude modulation 2 marks questions and answers. The angle modulation is classified as frequency modulation and phase modulation. Communication involves the transmission, reception and processing of information by electrical means. The relative amplitudes of the spectral lines depend on the value of jn. Quadrature frequency and phase demodulation radio frequency. The frequency modulation is also classified as narrow band width frequency modulation and wide band width frequency modulation. The process that transforms a message signal into an angle modulated signal is a nonlinear one. Amplitude modulation definition, types, solved examples.
Frequency modulation and phase modulation are also obtained in a similar way. For angle modulation, the modulated carrier is represented by. The separation ofthe am and fm components are illustrated as a modulation phenomenon in fig. Amplitude modulation of a sine or cosine carrier results in a variation of the carrier am plitude that is proportional to the. Multiple choice questions and answers on modulation and demodulation. The other type of modulation in continuouswave modulation is the angle modulation. This is further divided into frequency and phase modulation. This approach is called angle modulation, and includes frequency modulation fm and phase modulation pm. Frequency modulation and phase modulation are closely related. 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. 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.
Multiple choice questions and answers on modulation and. The amplitude of the carrier is maintained constant. The standard equation of the angle modulated wave is in amplitude modulation, the. Demodulation of ssb waves, vestigial side band modulation. This makes analysis of these signals more difficult. Amplitude modulation is a system of modulation in which the amplitude of the. 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. Analog communication angle modulation tutorialspoint. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm. Transmitter and receiver are simple in amplitude modulation. 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. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that. 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.
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 am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. We see that the amplitude spectrum is symmetrical about f c. 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. We use modulation technique to alter signals in time and frequency to accomplish desired objectives.
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. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Modulationtypesamplitude,frequency,phase modulation. Vsb modulation with envelope detection is used to modulate image in analog tv signals. It is a nonlinear process that generates additional frequencies, as we will see. Jun 17, 2018 in this video, i have explained amplitude modulation by following outlines. 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. The amplitude modulation receiver will be wider when compared to the fm receiver. Pdf analog communication system pdf notes ac notes sw. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast. The reason is that an lti system preserves the sinusoids.
Frequency and phase, or angle, modulation systems on the other hand are nonlinear. 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. Amplitude fluctuations can be measured with a simple detector such as. 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. Modulation plays vital role in the field of communication. Accordingly it is worth looking at some of the disadvantages of amplitude modulation. A modem is an equipment that performs both modulation and demodulation. Amplitude modulation am is an analog and linear modulation process as opposed to frequency modulation fm and phase modulation pm. Angle modulation is the process in which the frequency or the phase of the carrier signal varies according to the message signal. Amplitude modulation and demodulation 2017 frank dorenberg n4spp v1. Vsb signals are generated using standard am or dsbsc modulation, then passing modulated signal through a sideband shaping. Angle cw modulation with noise in the analysis of pm and fm systems, demodulation will be represented by yt.