AM Modulators, SSB

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AM Modulators, SSB

• Analog and Digital Communications
• Autumn 2005-2006

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AM Power Calculations
Lets calculate power in carrier and sidebands
(in one sideband)
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AM Power Calculations
At least 50 power is wasted in carrier
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DSB-SC or Simple DSB
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DSB Power Calculations
How does AM compare with DSB?
(Criteria for good modulation!)
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Power Calculations
For DSB-SC or DSB
For DSBC or AM
(100 modulation)
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Tone Modulation
For DSB-SC or DSB
For DSBC or AM
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Tone Modulation
For DSB-SC or DSB
For DSBC or AM
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Modulators

• Product modulators
• Require analog multipliers
• Variable trans-conductance multipliers
• Hall effect devices
• Hard to build
• Generally limited by low power and low
  frequencies
• Modulators based on filtering undesired
  frequencies
• Square-law and balanced modulators
• Ring modulator
• Switching modulator
• Avoid heavy filtering by not generating higher
  frequencies

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SSB-AM
First consider DSB-SC
Pass it through an SSB filter
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SSB and DSB Comparison
For DSB
For SSB
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Tone Modulation SSB DSB
For DSB-SC or DSB
For USSB
For LSSB