Types of modulation .pptx

This helps you types of analog modulation

1. ANALOG COMMUNICATION SYSTEMS By Ms. Swati Shrrpal Halunde Assistant Professor DEPT. of E.C.E S.I.T.C.O.E. Yadrav-Ichalkaranji Types of Modulation

2. Types of Modulation

3. Types of Modulation Amplitude Modulation : Amplitude of the carrier is varied in accordance with the instantaneous values of modulating signal. Frequency Modulation : Frequency of the carrier is varied in accordance with the instantaneous values of modulating signal. Phase Modulation : Phase of the carrier is varied in accordance with the instantaneous values of modulating signal.

4. Benefits or Need of Modulation To reduce the length or height of antenna For multiplexing For narrow banding or to use antenna with single or same length To reduce noise effect To avoid equipment limitation or to reduce the size of the equipment.

5. Amplitude Modulation The amplitude of the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal.

6. Amplitude Modulation The carrier signal is given by, C(t) = Ac Cosw c t Where, Ac= Maximum amplitude of the carrier signal. W= 2πfc= Frequency of the carrier signal. Modulating or baseband signal is given by, X(t) = Am Cosw m t Where, Am = Amplitude of the baseband signal.

7. Amplitude Modulation Th e s t a nd a r d e q u a t ion f o r a mpl i t ud e m odu l a t e d signal is expressed as, S(t)= Ac Cos2πf c t[1+m a (Cos2πf m t)] Where, m a = A m /A c = Modulation Index Time Domain representation of AM : S(t)=AcCos2πf c t+μAc/2Cos[2πf c +2πf m ]t+μAc/2Cos[2πf c -2πf m ]t I term: Carrier signal with amplitude Ac and frequency fc. term: Amplitude= μAc/2, frequency= f c +f m , Upper sideband frequency term: Amplitude= μAc/2, frequency= f c -f m , Lower sideband frequency

8. Amplitude Modulation Frequency Domain representation of AM : T h e ti me d o ma i n r e p r es e n t a ti o n o f AM w a v e is given by, S(t)= Ac Cos2πf c t[1+m a (Cos2πf m t)] Taking Fourier transform on both sides, S(f) = A c /2[δ(f-f c )+ δ(f+f c )] + A c m a /2[M(f-f c )+ M(f+f c )]

9. Modulation Index Modulation index or depth of modulation is given by, m a = [Amax-Amin/ Amax+Amin]= A m /A c Percentage of modulation index is, %m a = [Amax-Amin/ Amax+Amin]X100= [A m /A c ]X100 Types of AM with respect to modulation index : Under Modulation (m a <1) Critical Modulation (m a =1) Over Modulation (m a >1)

10. Types of AM