Angle Modulation in Telecommunication

1. Introduction in Telecommunication(121009) Chris Roeloffzen Chair: Telecommunication engineering (EWI) Floor 8 HOGEKAMP EL/TN building (north) Telephone 489 2804 E-mail: c.g.h.roeloffzen@el.utwente.nl

2. Today: Lecture 6 Chapter 7: Angle Modulation Transmission

3. Contents of the course Lecture 1 - 3: Introduction Chapter 1: Introduction to Electronic Communications Chapter 2: Signal Analysis and Mixing Lecture 4 - 7: CW modulation Chapter 4: Amplitude modulation, Transmission Chapter 5: Amplitude modulation, Reception Chapter 6: Single-side banded Communication Systems Chapter 7: Angle Modulation Transmission Chapter 8: Angle Modulation Receivers Lecture 8 - 11: Media Chapter 12: Metallic Transmission Lines Chapter 14: Electromagnetic Wave Propagation Chapter 15: Antennas Chapter 13: Optical Fibers Lecture 12 - 14: Digital Communication Chapter 9: Digital Modulation Chapter 10: Digital Transmission Lecture 15 & 16: ????????????????? For specific information see: www.el.utwente.nl/te/education/education.htm

4. Chapter 7: Angle Modulation Transmission • What is Angle modulation • What is the difference between frequency and phase modulation • What is direct and indirect modulation • Deviation sensitivity, phase deviation, modulation index • Bandwidth of angle-modulated wave • Bandwidth requirements • Phasor representation of angle-modulated wave • Frequency up-conversion • FM transmitters • Angle modulation versus AM

5. Angle modulation inst(t) = instantaneous phase (radians) Question: What is the instantaneous frequency?

6. Angle modulation vanglemod (t) = angle modulated wave (Volt) Vc = peak carrier amplitude (Volt) inst = instantaneous angular frequency (rad/sec) inst = instantaneous phase (radians)

7. Phase modulation The instantaneous phase of a harmonic carrier signal is varied in such a way that the instantaneous phase deviation i.e. the difference between the instantaneous phase and that of the carrier signal is linearly related to the size of the modulating signal at a given instant of time.

8. Phase modulation The instantaneous phase of a harmonic carrier signal is varied in such a way that the instantaneous phase deviation i.e. the difference between the instantaneous phase and that of the carrier signal is linearly related to the size of the modulating signal at a given instant of time. Kpis the phase deviation sensitivity (rad/Volt)

9. Frequency modulation The frequency of a harmonic carrier signal is varied in such a way that the instantaneous frequency deviation i.e. the difference between the instantaneous frequency and the carrier frequency is linearly related to the size of the modulating signal at a given instant of time.

10. Frequency modulation The frequency of a harmonic carrier signal is varied in such a way that the instantaneous frequency deviation i.e. the difference between the instantaneous frequency and the carrier frequency is linearly related to the size of the modulating signal at a given instant of time. Kfis the frequency deviation sensitivity

11. PM: Kp is the deviation sensitivity FM: Kf is the deviation sensitivity TASK: Make block diagrams of PM and FM modulators

12. PM: Kp is the deviation sensitivity Modulating signal source Phase modulator PM wave Direct Modulating signal source Differentiator Frequency modulator PM wave Indirect

13. FM: Kf is the deviation sensitivity Modulating signal source Frequency modulator Direct FM wave Modulating signal source Integrator Phase modulator FM wave Indirect

14. Frequency modulation of single frequency signal PM: FM:

15. PM and FM of sine-wave signal Carrier Modulating signal ? ?

16. PM and FM of sine-wave signal Carrier Modulating signal FM PM

17. Phase Deviation and Modulation Index mis the peak phase deviation or modulation index PM: (radians) FM: (unitless)

18. Frequency Deviation FM: FM PM (peak) frequency deviation dependent of the frequency PM: (peak) frequency deviation independent of the frequency

19. PM and FM of sine-wave signal

20. Bessel function of the first kind mis the modulation index FM PM is the Bessel function of the first kind

21. Relation AM and angle mod

22. Bessel function of the first kind

23. Bandwidth requirements of Angle-mod waves 1 Low-index modulation (narrowband FM) m< 1 ( fm >>> f ) (Hz) 2 High-index modulation (wideband FM) m> 10 (f >>> fm) 3 Actual bandwidth (look at Bessel table page 266) where n is the number of significant sidebands 4 Carson’s rule (approx 98 % of power)

24. Example FM modulator f = 10 kHz fm = 10 kHz Vc = 10 V fc = 500 kHz Draw the spectrum? What is the bandwidth using Bessel table? What is the bandwidth using Carson’s rule?

25. Example f = 10 kHz fm = 10 kHz Vc = 10 V fc = 500 kHz m=1 Fig 7-7

26. Phasor representation of Angle-mod wave m< 1 (narrowband FM) Fig 7-9

27. Phasor representation of Angle-mod wave m>> 1 (Wideband FM) Fig 7-10

28. Average Power of Angle-mod wave Instantaneous power in unmodulated carrier is (W) Pc = carrier power (Watts) Vc = peak unmodulated carrier voltage (volts) R = load resistance (ohms) Instantaneous power in angle-mod carrier is So the average power of the angle-mod carrier is equal to the unmodulated carrier

29. Frequency and Phase modulators Direct FM Modulator Fig 7-16

30. Linear integrated-circuit direct FM modulator High-frequency deviations and high modulation indices. Fig 7-20

31. Frequency up-conversion heterodyne method With FM and PM modulators, the carrier at the output is generally somewhat lower than the desired frequency of transmission Fig 7-24 a

32. Frequency up-conversion multiplication Fig 7-24

33. Indirect FM Transmitter Fig 7-27

34. Indirect FM Transmitter m < 1 Fig 7-28 Problem !!!!!!

35. Indirect FM Transmitter m < 1 Fig 7-28 max = m = 1.67 miliradiance  f=14 Hz Aim f = 75 kHz and ft = 90 MHz

36. Armstrong Indirect FM Transmitter Where are the frequency conversions ? Fig 7-27 Aim f = 75 kHz and ft = 90 MHz

37. Angle mod versus AM • Advantages of Angle modulation • Noise immunity • Noise performance and signal-to-noise improvement • Capture effect • Power utilization and efficiency • Disadvantages of Angle modulation • Bandwidth • Circuit complexity and costs

38. End