sir i am not able to understand topic4 of communication systems.please help me with some formulae...

the topic is :AMPLITUDE MODULATION.I AM UNABLE TO UNDERSTAND EVEN A BIT OF IT.PLEASE HELP.

Block diagram of Amplitude modulation: As you know, modulation is the process of varying one or more properties of a high frequency carrier signal, with respect to the message signal. Different types of modulation are: amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM).
Amplitude modulation: 
Amplitude modulation is the process of varying the amplitude of the carrier signal in accordance with the amplitude of the message signal. One important parameter associated with AM is the modulation index μ. Modulation index is the ratio of amplitude of message signal to that of the carrier signal.
 
That is,
 
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Practically, modulation index is kept less than or equal to 1, to avoid distortion of signals.
Amplitude modulated signals can be produced by adding the carrier signal with the message signal and passing the resultant signal through a square law device (eg: FET). Then the signal from the square law device is passed through band pass filter to allow only the signals centered at carrier frequencies to pass. The output of the band pass filter is power amplified and transmitted by the antenna.


 

Amplitude modulation:

• Initially, the modulating signal m(t) is added to the carrier signal c(t) to produce the signal x(t).
• The signal x(t) is allowed to pass through square law device to produce the output y(t).
• The output y(t) is given to band pass filter rejects dc and gives out the Amplitude modulated wave.