1. Bandpass Modulation and Demodulation
1. Why Modulate?
2. Signals and Noise
3. Digital Bandpass Modulation Techniques,
4. Detection of Signals in Gaussian Noise
5. Coherent Detection
6. Noncoherent Detection
7. Error Perforance for Binary Systems
8. M-ary Signaling and Performance
9. Symbol Error Performance for M-ary Systems(M>2)
10.Conclusion
[1]
Ch3. Modulation and Demodulation

2. 3.1 Modulation  Digital symbol ==> Waveform
 Frequency translating (Carrier Modulation)
[2]
Ch3. Modulation and Demodulation

3. 3.2 Signals and Noise  Noise : Intersymbol Interference , Distortion
 r(t) => Receive signal s(t) => Sum of the transmitted signal
n(t) => Thermal noise
 The probability density function(pdf), p(n),of the zero-mean noise voltage is exressed as
p(n) = [ 1/ (2)1/2 ] exp [-1/2 (n/ )2]
2 => noise variance
The normalized or standardized Gaussian density function of a zero-mean process is obtained by assuming that =1.
The normalized pdf is shown sketched in Figure 1.7
[3]
Ch3. Modulation and Demodulation

4. [4]
Ch3. Modulation and Demodulation

5.  A Geometric View of Signals and Noise
[5]
Ch3. Modulation and Demodulation

6. [6]
Ch3. Modulation and Demodulation

7. [7]
Ch3. Modulation and Demodulation

8.  Waveform Energy
[8]
Ch3. Modulation and Demodulation

9.  Generalized Fourier Transforms Solution
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Ch3. Modulation and Demodulation

10.  Representing White Noise with Orthogonal Waveforms
[10]
Ch3. Modulation and Demodulation

11.  Variance of White Noise
White Noise : 광의의 정상적 확률과정 N(t)의 전력스펙트럼 밀도가
전주파수에 걸쳐 일정한 경우
[11]
Ch3. Modulation and Demodulation

12. 3.3 Digital Bandpass Modulation Techniques
 Carrier wave
s(t) = A(t) cos (t) (3.23)
(t) = w0t + (t) (3.24)
s(t) = A(t) cos [ w0t + (t) ] (3.25)
정보내용이 A(t)에 실리면 진폭변조 (t) =  0 = 정수
정보내용이 (t) = w0t + (t) 에 포함되면 각변조 s(t) = 정수
정보내용이 (t) 에 포함되면 위상변조
정보내용이 d(t)/dt = '(t) 에 포함되면 주파수변조
(t) = 2πfct + (t)
'(t) = 2πfct + '(t)
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13. [13]
Ch3. Modulation and Demodulation

14. [14]
Ch3. Modulation and Demodulation

15.  Phase Shift Keying
 Frequency Shift Keying
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Ch3. Modulation and Demodulation

16. S(t) = A cos wt (3.30)  Amplitude Shift Keying
 Amplitude Phase Keying
S(t) = A cos wt (3.30)
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Ch3. Modulation and Demodulation

17. 3.4 Detection of Signal in Gaussian noise
 Decision Regions
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Ch3. Modulation and Demodulation

18. Choose the si(t) whose index (3.35) corresponds to the max zi(t)
 Correlation Receiver
0 <= t <= T
i = 1, , M
r(t) = si(t) + n(t) (3.33)
Choose the si(t) whose index (3.35)
corresponds to the max zi(t)
z(T) = z1(T) - z2(T) (3.36)
z(T) =ai(T) + n0(T) i = 1, 2
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19. [19]
Ch3. Modulation and Demodulation

20. Decision line  Binary Decision Threshold [20]
Ch3. Modulation and Demodulation

21. [21]
Ch3. Modulation and Demodulation

22. 3.5 Coherent Detection  Coherent Detection of PSK [22]
Ch3. Modulation and Demodulation

23. [23]
Ch3. Modulation and Demodulation

24.  Sampled Matched Filter
r(k) = s(k) + n(k) k = 0, 1, . . .
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Ch3. Modulation and Demodulation

25.  Coherent Detection of Multiple Phase Shift keying
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Ch3. Modulation and Demodulation

26. [26]
Ch3. Modulation and Demodulation

27. [27]
Ch3. Modulation and Demodulation

28.  Coherent Detection on FSK
[28]
Ch3. Modulation and Demodulation

29. [29]
Ch3. Modulation and Demodulation