lecture5

lecture5 - Lecture Outline Amplitude Modulation, More Power...

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Lecture Outline Amplitude Modulation, More Power Analysis, SSB-AM Reading: Text 3.2.2 , 3.2.3. Ignore details Material covered: 1. More on Conventional AM. Conventional AM use bandwidth of 2W with a carrier: ) 2 cos( )] ( 1 [ ) ( c c c t f t m A t u θ π + + = Modulation index is a which is the ratio of the smallest value of m ( t ). Spectrum of Conventional AM: For DSB-SC (suppressed carrier), the modulated signal power is m c u P A P 2 2 = For Conventional AM, the modulated power is m c c u P a A A P 2 2 2 2 2 + = Modulation efficiency is: m m P a P a 2 2 1 + = η . Since a < 1, we always have 5 . 0 Signal to noise ratio is W N P N S u 0 = In practice we use power law modulation for generating Conventional AM. Nonlinear device characteristics: ) ( ) ( ) ( 2 2 1 t v a t v a t v in in out + = t f A t m t v c c in 2 cos ) ( ) ( + = 2 2 1 ) 2 cos ) ( ( ) 2 cos ) ( ( ) ( t f A t m a t f A t m a t v c c c c out + + + = Band-pass filter:
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2. SSB-AM
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This note was uploaded on 11/01/2009 for the course EEE 455 taught by Professor Hui during the Spring '09 term at ASU.

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lecture5 - Lecture Outline Amplitude Modulation, More Power...

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