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![Amplitude Modulation
The standard equation for amplitude modulated
signal is expressed as,
S(t)= Ac Cos2πfct[1+ma(Cos2πfmt)]
Where, ma = Am/Ac = Modulation Index
Time Domain representation of AM:
S(t)=AcCos2πfct+μAc/2Cos[2πfc+2πfm]t+μAc/2Cos[2πfc-2πfm]t
I term: Carrier signal with amplitude Ac and frequency fc.
II. term: Amplitude= μAc/2, frequency= fc+fm , Upper sideband
frequency
III.term: Amplitude= μAc/2, frequency= fc-fm , Lower sideband
frequency](https://image.slidesharecdn.com/ppt-2-230829145051-66fa889f/75/Types-of-modulation-pptx-7-2048.jpg)
![Amplitude Modulation
Frequency Domain representation of AM:
The time domain representation of AM wave is
given by,
S(t)= Ac Cos2πfct[1+ma(Cos2πfmt)]
Taking Fourier transform on both sides,
S(f) = Ac/2[δ(f-fc)+ δ(f+fc)] + Acma/2[M(f-fc)+ M(f+fc)]](https://image.slidesharecdn.com/ppt-2-230829145051-66fa889f/75/Types-of-modulation-pptx-8-2048.jpg)
![Modulation Index
Modulation index or depth of modulation is given
by,
ma = [Amax-Amin/ Amax+Amin]= Am/Ac
Percentage of modulation index is,
%ma = [Amax-Amin/ Amax+Amin]X100= [Am/Ac ]X100
Types of AM with respect to modulation index:
• Under Modulation (ma <1)
• Critical Modulation (ma =1)
• Over Modulation (ma >1)](https://image.slidesharecdn.com/ppt-2-230829145051-66fa889f/75/Types-of-modulation-pptx-9-2048.jpg)
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Types of modulation .pptx
- 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.
- 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 Needof 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 amplitudeof the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal.
- 6. Amplitude Modulation The carriersignal is given by, C(t) = Ac Coswct 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 Coswmt Where, Am = Amplitude of the baseband signal.
- 7. Amplitude Modulation The standardequation for amplitude modulated signal is expressed as, S(t)= Ac Cos2πfct[1+ma(Cos2πfmt)] Where, ma = Am/Ac = Modulation Index Time Domain representation of AM: S(t)=AcCos2πfct+μAc/2Cos[2πfc+2πfm]t+μAc/2Cos[2πfc-2πfm]t I term: Carrier signal with amplitude Ac and frequency fc. II. term: Amplitude= μAc/2, frequency= fc+fm , Upper sideband frequency III.term: Amplitude= μAc/2, frequency= fc-fm , Lower sideband frequency
- 8. Amplitude Modulation Frequency Domainrepresentation of AM: The time domain representation of AM wave is given by, S(t)= Ac Cos2πfct[1+ma(Cos2πfmt)] Taking Fourier transform on both sides, S(f) = Ac/2[δ(f-fc)+ δ(f+fc)] + Acma/2[M(f-fc)+ M(f+fc)]
- 9. Modulation Index Modulation indexor depth of modulation is given by, ma = [Amax-Amin/ Amax+Amin]= Am/Ac Percentage of modulation index is, %ma = [Amax-Amin/ Amax+Amin]X100= [Am/Ac ]X100 Types of AM with respect to modulation index: • Under Modulation (ma <1) • Critical Modulation (ma =1) • Over Modulation (ma >1)
- 10.