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er Principles of Elect ___ Amplitude Modulation, , Definition :, , tronics Cc Comm. _ (E&To/S /Sem n 3/MSBTE) 2-2 _, , , , _ In the modulation process some parameter of the carrier wave (such as amplitude, frequency or phase) is varied in proportion with, the modulating signal., , _ The result of this process is called as the modulated signal. This modulated signal is then transmitted by the transmitter over a, communication channel or medium., , _ The receiver will "Demodulate" the received modulated signal and get the original information signal back. Thus demodulation is, exactly opposite to modulation., , - In the process of modulation, the carrier wave actually acts as a carrier which carries the information signal (modulating signal), from the transmitter to receiver., , — — This is similar to a situation in which a person travels in his car or on his bike from one place to the other. The person can be viewed, as the modulating signal and the car or bike as the carrier as shown in Fig. 2.2.2., , Information, signal, , Carrier, , (-9) Fig. 2.2.2 : Concept of modulation, , 2.2. i Types of Modulation ee : Sau, :, , , , Q.1 Define pulse modulation arid state its t - Wecan classify the modulation techniques into two categories :, , 1. Continuous wave modulation. 2. Pulse modulation., - The classification of modulation techniques is shown in Fig. 2.2.3., , Modulation, Continuous wave Pulse modulation, modulation(Analogy, Analog pulse Digital pulse, Amplitude Frequency Phase modulation modulation, , modulation modulation modulation, (A.M.) (F.M.) (P.M.), , PCM DM ADM, PAM PWM ~ PPM, , (-1304)Fig. 2.2.3 : Classification of modulation process, 2.2.2 Continuous Wave Modulation :, , - Incontinuous wave (CW) modulation, the carrier is usually sinusoidal (sinewave or cosinewave). Its frequency is much higher than, the frequency of the modulating signal., , Depending on which parameter of the carrier is changed the continuous wave modulation are classified into three Categories :, 1. A.M. (Amplitude Modulation), , 2. _F.M. (Frequency Modulation), , 3. P.M. (Phase Modulation)