Chapter 3a Amplitude Modulation

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Chapter 3a: AMPLITUDE MODULATION

What is Modulation? A process of converting the baseband signal to a form suitable for transmission.

3 Types of Modulation:

Amplitude Modulation

Frequency Modulation

Phase Modulation

Reasons for modulation

Chapter 3a: Amplitude Modulation

Overmodulation When m > 1 (Em > Ec), overmodulation occurs:

Causing envelope distortion to occur (phase reversal or clipping)

Thus, information signal cannot be recovered accurately

and creating new frequencies, causing the signal to have a larger bandwidth.

May cause interference to other adjacent channels

About AM DSBFC Signal Power:

Pc is not affected by modulation process

m increase, Ptotal also increase

when m = 1, the power of USB and LSB is half that of carrier (33% of the total power)

Thus, it is inefficient, because USB and LSB carries same info while carrier carries no info.

For efficiency, use m as high as possible but not over 1.