Modulation

1. Modulation
Subject: Measurement sciences and techniques
Submitted by: Chandan, EE Department, NITTTR, Chandigarh

2. Modulation-Modulation means to ’change’ or ’to modify’
the carrier signal in accordance with the
information signal
-It is basically multiplication of signal
carrying information by a carrier wave of
constant frequency and amplitude

3. In Modulation, the
message signal is used to
control the parameters of
the carrier signal so as to
impose the information
onto the carrier

4. Modulation
Circuit
Message
signal Fs(t)
Carrier
signal Fc(t)
Modulated
signal
Fc(t) Fs(t)

5. Informationcanbeaddedtothesignalby:-
1.Changing its Amplitude
2.Changing its Frequency
3.Changing its Phase
4.Changing its Polarization
5.Changing its Spin

6. Informationcanbeaddedtothesignalby:-
1.Changing its Amplitude
2.Changing its Frequency
3.Changing its Phase
4.Changing its Polarization
5.Changing its Spin

7. Informationcanbeaddedtothesignalby:-
1.Changing its Amplitude
2.Changing its Frequency
3.Changing its Phase
4.Changing its Polarization
5.Changing its Spin

8. Whereismodulation
used?

9. Whereis
modulationused?Mostly applied to electromagnetic
signals in applications like
1.Radio
2.Laser/optics
3.Computer Networks

10. Types of
Modulation
Continuous
Wave
Modulation
Amplitude
Modulation
Angular
Modulation
Frequency
Modulation
Phase
Modulation
Pulse digital
Modulation
Digital
Modula
tion
Pulse
code
Modulati
on
Analo
g
Modu
lation
Pulse
Amplitu
de
Modula
tion
Pulse
Duration
Modulatio
n
Pulse
Position
Modulat
ion

11. Amplitudemodulation
The signal or information modulates the
amplitude of the carrier
This modification of the amplitude of the carrier
is in proportion to the amplitude of the
modulating signal

12. Amplitude
Modulation
Circuit
Message
signal Fs(t)
Carrier
signal Fc(t)
Modulated
signal
Fc(t) Fs(t)

16. BoththeCarrierand
MessageSignalsshould
haveDifferent
Frequencies.

17. BoththeCarrierand
MessageSignals
shouldhaveDifferent
Frequencies

18. Mathematically
Es=As sin ws t
Ec=Ac sin wc t
Where ws ≠ wc

19. Mathematically
Es=As sin ws t
Ec=Ac sin wc t
Where ws ≠ wc
But what is the
relation between
ws and wc

20. Mathematically
Es=As sin ws t
Ec=Ac sin wc t
Where ws ≠ wc
ws < wc

21. Mathematically
Es=As sin ws t
Ec=Ac sin wc t
Where ws ≠ wc
And what about
As and Ac

22. Mathematically
Es=As sin ws t
Ec=Ac sin wc t
Where ws ≠ wc
As < Ac

23. Output = (As sin ws t)( Ac sin wc t)
= AsAc [cos(wc-ws)t – cos (wc+ws)t]
2

24. Output = (As sin ws t)( Ac sin wc t)
= AsAc [cos(wc-ws)t – cos (wc+ws)t]
2
Side Band Frequencies

26. AnotherWaveform
Example……

29. Use
of
Amplitude
Modulation…

31. Air
Band
Radio

32. Air band
- group of frequencies for radio
communication in civil aviation
-Also used for
Radio navigational aids
and air traffic control

33. Amplitude
Modulation
Circuits

34. Electromechanical Chopper
Output

35. Electromechanical Chopper

36. Semiconductor Modulator
Output

37. Semiconductor Modulator

38. WhyTransformerisused
inmodulatorcircuits?

39. Frequency
Modulation

40. Frequencymodulation
The signal or information modulates the
frequency of the carrier
The frequency of the carrier wave is changed in
accordance with the intensity of the information
signal

41. How does
Frequency modulation
affects the amplitude
and phase
of the carrier wave ?

45. Use
of
Frequency
Modulation…

46. 1.MagneticTape
2.Radio

47. Difference Between AM and FM
AM FM
Frequency
Range
540-1650
KHz
88-108MHz
Power
Consumption Lower Higher
Signal
quality
Inferior Superior

48. Thankyou!