Notes
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
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.
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- Undergraduate UEET2513 Analogue Communications Note on Chapter 3a Amplitude Modulation, created by Lloyd Teoh on 28/07/2015.
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- Lloyd Teoh · Jul 2015
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- Feb 19, 2016
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