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__ Amplitude Modulation, , , , 1. Amplitude Modulation [AM] :, Amplitude of the carrier is varied in proportion with the instantaneous amplitude of the baseband signal keeping its frequency ang, , Phase constant., 2. Frequency Modulation [FM] :, Frequency of the carrier is varied in proportion with the instantaneous amplitude of the baseband signal keeping its amplitude ang, phase constant., 3. Phase Modulation [PM] :, — Phase of the carrier is modified in proportion with the instantaneous amplitude of the baseband signal keeping the other two, , Parameters constant., — The continuous wave modulation is the type of analog modulation. So AM, FM and PM are the examples of analog modulation,, , 2.2.3. Pulse Modulation : Sak, , MSBTE Questions, , Q.1_Define puise modulation and state its types., , , , — In pulse modulation, the carrier is in the form of train of periodic rectangular pulses., , — Pulse modulation can be either analog or digital., , — In the analog pulse modulation, the amplitude, width or Position of the rectangular carrier pulses is changed in accordance with the, modulating signal. /, , — This will result in PAM (Pulse Amplitude Modulation), PWM (Pulse Width Modulation) or PPM (Pulse Position Modulation), respectively., , — PAM, PWM and PPM are the examples of analog pulse modulation., , — The pulse modulation can be digital as well. The well known examples of digital pulse modulation are Pulse Code “Modulation, (PCM), Delta Modulation (DM), Adaptive Delta Modulation (ADM) etc., , 2.2.4 Frequency Translation in the Modulation Process :, , — The baseband signal or modulating signal is a low frequency signal. For example the audio signal is present in the frequency range, from 20 Hz to 20 kHz., , — But due to modulation, the same signal now gets translated to a higher frequency range., , - For example the Vividh Bharati FM Pune station is tuned at 101 MHz, or AM Pune station is at 792 kHz., , 2.2.5 Multiplexing :, , — Multiplexing is the process of combining several message signals together and send them over the same communication channel., - Three commonly used methods of multiplexing are :, , 1. Frequency Division Multiplexing (FDM)., , 2. Time Division Multiplexing (TDM)., , 3. Code Division Multiplexing (CDM)., , TT III