Principles of Communication Systems
Lecture 06
Angle Modulation
FM and PM
Content
1.
2.
3.
4.
5.
Time-varying frequency
Introduction to angle modulation
Relationship between FM and PM
FM bandwidth
FM modulation and demodulation
Angle Modulation
2
1. Instantaneous Frequency
Angle Modulation
3
Instantaneous Frequency

Angle Modulation
4
2. Phase Modulation (PM) & Frequency Modulation
(FM)
Angle Modulation
5
3. Relationship Between FM and PM
Angle Modulation
6
FM Example
Angle Modulation
7
PM Example
Angle Modulation
8
Frequency Shift Keying (FSK)
Angle Modulation
9
Phase Shift Keying (PSK)
Angle Modulation
10
PSK: Direct Modulation
Angle Modulation
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4. Bandwidth of Angle Modulation
 FM Frequency
fi  fc 
kf
2
f 
 Frequency peak deviation in FM
 PM frequency
fi  fc 
kp
2
 Frequency peak deviation in PM
 Deviation ratio
Angle Modulation
f

B
m(t )
m (t )
f 
m p  [| m(t ) |]max
k f mp
2
m' p  [| m (t ) |]max
k p m' p
2
12
Narrowband FM
Angle Modulation
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Narrowband FM
Angle Modulation
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Bandwidth of Angle-Modulated Waves
Angle Modulation
15
Tone Frequency Modulation
Angle Modulation
16
Fourier Transform of Tone FM
Angle Modulation
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Wideband FM (WBFM) Bandwidth
Angle Modulation
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Wideband FM (WBFM) Bandwidth
Angle Modulation
19
Wideband FM (WBFM) Bandwidth
Angle Modulation
20
Frequency Modulation of Tone
Angle Modulation
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Bessel Function
Angle Modulation
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Example
Angle Modulation
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Broadcast FM
Angle Modulation
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5. NBFM Modulation
Angle Modulation
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NBFM Block Diagram
Angle Modulation
26
NBFM: Bandpass Limiter
Angle Modulation
27
NBFM: Bandpass Limiter
Angle Modulation
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WBFM Modulation: Direct Generation Using VCO
Angle Modulation
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VCO Using Varactor
Angle Modulation
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Armstrong’s Indirect Method
Angle Modulation
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FM Demodulation
Angle Modulation
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Derivative Theorem for Fourier Transform
Angle Modulation
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Slope-Detecting Filter
Angle Modulation
34
FM Demodulator and Differentiator
Angle Modulation
35
Envelope Detection using Ideal Differentiator
Angle Modulation
36
FM Detection Circuits
Angle Modulation
37
Advantages of FM
Angle Modulation
38
Advantages of FM
Angle Modulation
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Noise and FM
Angle Modulation
40
FM Preemphasis and Deemphasis
Angle Modulation
41
FM Preemphasis and Deemphasis
Angle Modulation
42
References
 John Pauly, Analog and Digital Communication Systems, lecture
notes.
 Lathi & Ding, Modern Digital and Analog Communications
Systems, 4th ed
Angle Modulation
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