1. Department of Electrical and Computer Engineering
ECE 4371, Fall, Introduction to Telecommunication Engineering/Telecommunication Laboratory
                                                           
Zhu Han
Department of Electrical and Computer Engineering
Class 3
Sep. 11st, 2017

2. Overview
Homework
4.2.1, 4.2.3, 4.2.5, 4.2.7, 4.2.9
4.3.3, 4.3.8
4.4.2, 4.4.4
4.5.2
4.8.1
Due 9/25/17
FDM system, section 4.7
Analog TV, section 4.9
Phase-locked loop, Section 4.8
FM basics

3. Block diagram of FDM system.

4. FMA of SSB for Telephone Systems

5. Illustrating the modulation steps in an FDM system

6. AM Broadcasting Limitation History Frequency Long wave: 153-270kHz
Medium wave: 520-1,710kHz, AM radio
Short wave: 2,300-26,100kHz, long distance, SSB, VOA
Limitation
Susceptibility to atmospheric interference
Lower-fidelity sound, news and talk radio
Better at night, ionosphere.

7. Superheterodyne vs. homodyne
Move all frequencies of different channels to one medium freq.
In AM receivers, that frequency is 455 kHz,
for FM receivers, it is usually 10.7 MHz.
Filter Design Concern
Accommodate more radio stations
Edwin Howard Armstrong

8. Eliminate flicker effects
Television
Digital Display (CRT)
Analog Display (TV)
Eliminate flicker effects

9. Deflection Signal and Synchronization
Deflection signal and synchronization signal
525525 30=8.27M

10. Solar Power and Human Eye

11. RGB, LIQ mL=0.3mr+0.59mg+0.11mb mI=0.6mr+0.28mg-0.32mb
mQ=0.21mr-0.52mg+0.31mb

12. Bandwidth
VSB and QAM

13. Comb Filtering

14. NTSC, PAL, and SECAM National Television System Committee
Low complexity, higher vertical color resolution
525 line/60Hz(30frames per second)
Phase Alternative Line: PAL
The phase of the color components is reversed from line to line
Robust to Multipath, phase distortion
625line/50Hz(25 frames per second), slightly larger bandwidth
SECAM
Requires the receiver to memorize the content of each line
Mono when used for different standards

15. TV standards in the world

16. Carrier Recover Error DSB: e(t)=2m(t)cos(wct)cos((wc+ w)t+)
e(t)=m(t) cos((w)t+)
Phase error: if fixed, attenuation. If not, shortwave radio
Frequency error: catastrophic beating effect
SSB, only frequency changes, f<30Hz.
Donald Duck Effect
Crystal oscillator, atoms oscillator, GPS, …
Pilot: a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes.

17. Phase-Locked Loop
Can be a whole course. The most important part of receiver.
Definition: a closed-loop feedback control system that generates and outputs a signal in relation to the frequency and phase of an input ("reference") signal
A phase-locked loop circuit responds both to the frequency and phase of the input signals, automatically raising or lowering the frequency of a controlled oscillator until it is matched to the reference in both frequency and phase.

18. Voltage Controlled Oscillator (VCO)
W(t)=wc+ce0(t), where wc is the free-running frequency
Example

19. Ideal Model Model Sp Si So LPF Sv VCO Capture Range and Lock Range
Si=Acos(wct+1(t)), Sv=Avcos(wct+c(t))
Sp=0.5AAv[sin(2wct+1+c)+sin(1-c)]
So=0.5AAvsin(1-c)=AAv(1-c)
Capture Range and Lock Range Si Sp So
LPF Sv
VCO

20. Phase and Frequency Acquisition

21. Carrier Acquisition in DSB-SC
Signal Squaring method
Costas Loop
SSB-SC not working

22. PLL Applications Clock recovery: no pilot Deskewing: circuit design
Clock generation: Direct Digital Synthesis
Spread spectrum:
Jitter Noise Reduction
Clock distribution

23. FM Basics VHF (30M-300M) high-fidelity broadcast
Wideband FM, (FM TV), narrow band FM (two-way radio)
1933 FM and angle modulation proposed by Armstrong, but success by 1949.
Digital: Frequency Shift Key (FSK), Phase Shift Key (BPSK, QPSK, 8PSK,…)
AM/FM: Transverse wave/Longitudinal wave

24. Angle Modulation vs. AM Summarize: properties of amplitude modulation
Amplitude modulation is linear
just move to new frequency band, spectrum shape does not change. No new frequencies generated.
Spectrum: S(f) is a translated version of M(f)
Bandwidth ≤ 2W
Properties of angle modulation
They are nonlinear
spectrum shape does change, new frequencies generated.
S(f) is not just a translated version of M(f)
Bandwidth is usually much larger than 2W

25. Angle Modulation Pro/Con Application
Why need angle modulation?
Better noise reduction
Improved system fidelity
Disadvantages
Low bandwidth efficiency
Complex implementations
Applications
FM radio broadcast
TV sound signal
Two-way mobile radio
Cellular radio
Microwave and satellite communications

26. Instantaneous Frequency
Angle modulation has two forms
- Frequency modulation (FM): message is represented as the variation of the instantaneous frequency of a carrier
- Phase modulation (PM): message is represented as the variation of the instantaneous phase of a carrier

27. Phase Modulation
PM (phase modulation) signal

28. Frequency Modulation FM (frequency modulation) signal
(Assume zero initial phase)

29. FM Characteristics Characteristics of FM signals
Zero-crossings are not regular
Envelope is constant
FM and PM signals are similar

30. Relations between FM and PM

31. FM/PM Example (Time/Frequency)

32. Frequency Modulation FM (frequency modulation) signal
(Assume zero initial phase)

33. Example
Consider m(t)- a square wave- as shown. The FM wave for this m(t) is shown below.
m(t)
T T

34. Frequency Deviation Frequency deviation Δf
difference between the maximum instantaneous and carrier frequency
Definition:
Relationship with instantaneous frequency
Question: Is bandwidth of s(t) just 2Δf?
No, instantaneous frequency is not
equivalent to spectrum frequency
(with non-zero power)!
S(t) has ∞ spectrum frequency
(with non-zero power).

35. Modulation Index
Indicate by how much the modulated variable (instantaneous frequency) varies around its unmodulated level (message frequency)
Bandwidth A

36. Narrow Band Angle Modulation
Definition
Equation
Comparison with AM
Only phase difference of Pi/2
Frequency: similar
Time: AM: frequency constant
FM: amplitude constant
Conclusion: NBFM signal is similar to AM signal
NBFM has also bandwidth 2W. (twice message signal bandwidth)

37. Example

38. Block diagram of a method for generating a narrowband FM signal.

39. A phasor comparison of narrowband FM and AM waves for sinusoidal modulation. (a) Narrowband FM wave. (b) AM wave.

40. Wide Band FM
Wideband FM signal
Fourier series representation

41. Example

42. Bessel Function of First Kind

43. Spectrum of WBFM (Chapter 5.2)
Spectrum when m(t) is single-tone
Example 2.2

44. Bandwidth of FM Facts Bandwidth of FM signal is approximately by
FM has side frequencies extending to infinite frequency  theoretically infinite bandwidth
But side frequencies become negligibly small beyond a point  practically finite bandwidth
FM signal bandwidth equals the required transmission (channel) bandwidth
Bandwidth of FM signal is approximately by
Carson’s Rule (which gives lower-bound)

45. Carson’s Rule Nearly all power lies within a bandwidth of
For single-tone message signal with frequency fm
For general message signal m(t) with bandwidth (or highest frequency) W