Slide 1 : Modulate means to change certain parameters of the carrier signal
Need for modulation
For Long distance wireless communication
Practical Height of an antenna
For Transmission of multiple channels
For Privacy Ronald Stanley Hoskeri
HF Carrier Signal : vc =Vc Sinct This is a carrier wave in other words it carries the information
to be transmitted it has a frequency which is much higher than
the modulating frequency HF Carrier Signal Vc Ronald Stanley Hoskeri
AF Modulating Signal : This is a modulating wave in other words the information
that needs to be transmitted.Generally it has a frequency which is
much less than the Carrier frequency. The subscript m indicates it is
Modulating voltage. vm =VmSinmt AF Modulating Signal Vm Ronald Stanley Hoskeri
What is Amplitude Modulation : What is Amplitude Modulation Well it is one of the techniques used for long distance communication.
Definition: Changing the amplitude of the carrier signal in accordance with that of modulating signal keeping frequency and initial phase constant. Ronald Stanley Hoskeri
Slide 5 : Well we need to note at this point that it is the carrier wave that needs to
be moderated ie changed and not the modulating signal.
As we all know that the high frequency carrier is represented by the
Equation vc =VcSin(ct + ) where initial phase is the origin = 0
Vc= Amplitude of the carrier
ct= Angular frequency
= Initial phase
There are three important parameters here that is
Vm : if the amplitude is varied keeping and ct constant then it is called
Amplitude modulation
ct : the frequency is varied keeping and Vc constant then it is called
Frequecy modulation
: If the initial phase is varied keeping frequency ct and
amplitude Vc constant then it is called as phase modulation Ronald Stanley Hoskeri
Double Side Band : Vc Vm Double Side Band This blue envelop that you see is the modulating signal t V -V Ronald Stanley Hoskeri
Actual Amplitude Modulated Wave : Vc Actual Amplitude Modulated Wave Ronald Stanley Hoskeri
Upper side band : Upper side band A=Vc + vm A= is the instantaneous change in the amplitude of the carrier
Vc= Amplitude of the un modulated carrier
vm= is the instantaneous modulating voltage Ronald Stanley Hoskeri
Lower Side Band : Lower Side Band A= - (Vc + vm) Ronald Stanley Hoskeri