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Angle Modulation Summer

This document discusses angle modulation techniques, including frequency modulation (FM) and phase modulation (PM). It explains that FM varies the frequency of a carrier signal based on an information signal, while PM varies the phase shift. The relationship between phase and frequency is described, and mathematical analysis of PM and FM is presented using concepts like modulation index, frequency deviation, and Bessel functions. Sidebands and bandwidth are also covered.

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DJ Amora
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69 views15 pages

Angle Modulation Summer

This document discusses angle modulation techniques, including frequency modulation (FM) and phase modulation (PM). It explains that FM varies the frequency of a carrier signal based on an information signal, while PM varies the phase shift. The relationship between phase and frequency is described, and mathematical analysis of PM and FM is presented using concepts like modulation index, frequency deviation, and Bessel functions. Sidebands and bandwidth are also covered.

Uploaded by

DJ Amora
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPTX, PDF, TXT or read online on Scribd
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Angle Modulation

Principles of Communications
ECE 011

Learning Outcome
After studying this section, you should be able to:
❑ Analyze angle modulation: FM and PM

djaamora@gmail.com
Review:
• Impressing an information signal on a carrier is called modulation
• A carrier wave can be modulated by varying its amplitude, frequency, or phase shift.

Carrier signal  

amplitude phase
Amplitude of the frequency
modulated signal

   
Frequency Modulation Phase Modulation
Impressing an information signal on a Impressing an information signal on a carrier
carrier by changing its FREQUENCY by changing its PHASE SHIFT produces
produces FM. PM.
Phase and Frequency Relationship

   

Whenever the frequency of a carrier is


 
  varied, the phase is also varied, and vice
versa.

 
 

5ms 8ms 20ms 30ms


Carrier signal

Information signal

Maximum Positive Deviation

+ Peak Voltage of the


Information Signal

Zero Deviation Zero Crossing Point of the


Information Signal

Maximum Negative Deviation F


- Peak Voltage of the M
Information Signal

FM Waveform
Carrier signal

Information signal
Carrier signal

Information signal
Maximum Positive Deviation

Zero Crossing Positive Going


point Of the information signal

Zero Deviation + and – voltage peaks of the


Information signal

Maximum Negative Deviation P


M
Zero Crossing Negative Going
point Of the information signal

PM Waveform
Carrier signal
 

Information signal  

F
M  

P
M
Mathematical Analysis: PHASE MODULATION
Information signal  

Carrier signal  

modulation
index of Kp is a constant and called deviation
PM sensitivities of the phase. Unit in
rad/V or deg/V.

 
Mathematical Analysis: FREQUENCY MODULATION
 
Information signal  
Carrier signal    

modulation
index of
FM

Frequency
deviation

 
Instantaneous Phase and Frequency
Information signal  

Carrier signal  

 
BESSEL Function

In FM, the number of sidebands are infinite.


BESSEL Function helps you identify the number of
significant sideband pairs and their amplitude in a
given modulation index.
Bessel Bandwidth = 2 n fm
n= # of sideband pairs
fm= modulating signal frequency

Bandwidth

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