Introduction to Communication Systems 4,eee330

1. EEE 330
Introduction to
Communication Systems
Lecture # 4
Angle Modulation and Demodulation

2. Overview
The Objectives of Today’s Lecture is to
introduce angle (or exponential) modulation
Analog Angle modulation is a non-linear
modulation technique that maps the message
signal to the angle of a transmitted carrier
There are two basic forms:
Phase Modulation (PM)
Frequency Modulation (FM)
Read Carlson et al, Chapter 5, Lathi 4.1 –
4.8

3. Analog Angle Modulation

4. PM and FM
There are two basic forms of angle
modulation
Frequency Modulation (FM)
Phase Modulation (PM)
FM – the frequency of the carrier is
varied linearly with the message signal
PM – the phase of the carrier is varied
linearly with the message signal

5. Frequency Modulation

6. FM

7. Phase Modulation

8. Non-linear Nature of Angle
Modulation

9. Non-linear modulation – cont.

10. Transmitted Signals for Angle
Modulation

11. Instantaneous Frequency

12. Description of Frequency
Modulation

13. FM vs. AM

14. Comparison of PM and FM:
Example #1

15. Comparison of PM and FM:
Example #2
FM signal shows continuous
frequency increase
PM signal has single frequency shift

16. Comparison of PM and FM:
Example #3 Frequency change for FM
Phase change for PM

17. Comparison of PM and FM:
Example #4

18. Equivalency of Frequency
Modulation and Phase Modulation

19. Comparison of FM and PM
They are very similar in signal
structure
Both allow designer to trade bandwidth
for power efficiency
FM has advantages in:
Ease of implementation
Performance in noise
Larger range of BW/performance trade-off
FM is used almost exclusively

20. FM – Tone Modulation

21. Sinusoidal Message Signal (Tone
Modulation)

22. Narrowband FM (NBFM)

23. NBFM

24. Resulting Distortion

25. NBFM Approximation

26. NBFM Approximation

27. Wideband FM – Tone modulation

28. WBFM - Tone modulation

29. Spectrum of Tone Modulation

30. Narrowband vs. Wideband FM

31. Spectrum

32. Spectrum

33. NBFM vs. WBFM

34. Example

35. Example- Cont.

36. Example- Cont.

37. Example- Cont.

38. Bandwidth

39. Example- Cont.

40. Bandwidth

41. Carson’s Rule – General Signals

42. Generation and Demodulation of
FM Signals

43. Generation of NBFM

44. Generation of WBFM

45. Generation of WBFM – Direct
Method

46. Generation of WBFM – Indirect
Method

47. Generation of WBFM – Indirect
Method

48. Demodulators for FM Signals

49. Practical Demodulators

50. Frequency Discriminator

51. Frequency Discriminator

52. Taking Derivative

53. Balanced Frequency Discriminator

54. Balanced Frequency Discriminator

55. Phased-Locked Loop (PLL)

56. PLL

57. PLL

58. Zero-crossing Detector