This is all about MODULATION, AMPLITUDE MODULATION, AND AM DEMODULATION, Techniques
By_ IMTIAZ ALI AHMED
B.Tech Student
Siliguri Institute of Technology(ECE)
1. SEMINAR PRESENTATION
ON
AMPLITUDE MODULATION AND DEMODULATION TECHNIQUE
Presentation By
IMTIAZ ALI AHMED
ROLL NO:-11900315020
DEPARTMENT OF ELECTRONICS & COMMUNICATION
ENGINEERING
SILIGURI INSTITUTE OF TECHNOLOGY
2. Content
What Is Modulation?
Why Do We Need Modulation?
Type of Modulation
AMPLITUDE MODULATION
Mathematical Equations of AM
Modulation Index
Type of Amplitude Modulation
Balance Modulator
Amplitude Demodulation
Type of Amplitude Demodulation
Envelope Detector
Synchronous Detector
Application of AM
References
3. What Is Modulation?
Modulation is define as the process by which some characteristics , usually
amplitude, frequency or phase, of a carrier is varied in accordance with
instantaneous value of some other voltage , called the modulating voltage.
It is the process of transmission of information signal (low frequency
signal) using a high frequency Carrier signal
4. Why Do We Need Modulation?
If we transmit the information signal directly. Signals from different
transmitters will get mixed up.
Baseband signals or low frequency signals could not transmitted without
modulation.
Antenna height :=l/4
c=nl
l=c/n
signal transmission with minimum noise.
6. AMPLITUDE MODULATION
The amplitude of the carrier is changing in accordance with the
instantaneous value of modulating signal
Information is contain in the envelope
7. Mathematical Equations of AM
Carrier Signal C(t)=
Modulating Message Signal m(t)=
The AM Signal sAM (t) =
Ac sin(2 fct) or Ac sin(ct)
Am sin(2 fmt) or Am sin(mt)
(Ac + Am sin(mt) ) sin(ct)
8. Modulation Index
The amount of modulation in AM signal is given by its modulation index:
= Am /Ac
When Am =Ac , =1 or 100% modulation.
Over-modulation, i.e. Am>Ac , should be avoided
because it will create distortions
= 1
> 1
< 1
9. Type of Amplitude Modulation
Double Sideband with full carrier (DSB-FC):The transmission of such a
signal which contains a carrier along with two sidebands, can be termed
as Double Sideband Full Carrier system, or simply DSB-FC. most widely
used AM.
10. Double Sideband Suppressed Carrier (DSB-SC):If this carrier is
suppressed and the saved power is distributed to the two sidebands, then
such a process is called as Double Sideband Suppressed Carrier system or
simply DSBSC.
11. Single Sideband with suppressed carrier(SSB-SC): The process of
suppressing one of the sidebands, along with the carrier and transmitting a
single sideband is called as Single Sideband Suppressed Carrier system,
or simply SSB-SC or SSB.
Vestigial Sideband(VSB): Modification of SSB
12. Balance Modulator
The balanced modulators are used to suppress the unwanted carrier in an AM
wave.
The carrier and modulating signals are applied to the inputs of the balanced
modulator and we get the DSB signal with suppressed carrier at the output
of the balanced modulator.
Thus the output consists of the upper and lower side bands only.
18. Application of AM
Entertainment - AM Radio (music, talk radio)
Business - CB Radio to relay shipment progress, conference calls
with other branches via telephone or speakerphone
Government - Police officers keeping contact with the station, or
relaying the information and location of a suspect
Personal - Cell phones or walkie-talkies for chatting with friends
Military - Using undetectable radio signals to communicate with
other soldiers, or voice commands to control weapons
19. References
Communication system by-Sanjay Sharma
https://en.wikipedia.org/wiki/Amplitude_modulation
en.wikipedia.org/wiki/Demodulation
Communication system Fourth Edition by Simon Haykin, from
chapter 2
Google//AM pdf
byjus.com/physics/modulation-need-modulation/