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AM Modulators, SSB

AM Modulators, SSB. Analog and Digital Communications Autumn 2005-2006. AM – Power Calculations. Lets calculate power in carrier and sidebands:. (in one sideband). AM – Power Calculations. At least 50% power is wasted in carrier. USB. LSB. LSB. USB. DSB-SC or Simple DSB.

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AM Modulators, SSB

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  1. AM Modulators, SSB Analog and Digital Communications Autumn 2005-2006 CS477: Analog and Digital Communications

  2. AM – Power Calculations Lets calculate power in carrier and sidebands: (in one sideband) CS477: Analog and Digital Communications

  3. AM – Power Calculations At least 50% power is wasted in carrier CS477: Analog and Digital Communications

  4. USB LSB LSB USB DSB-SC or Simple DSB CS477: Analog and Digital Communications

  5. ( is power in one sideband) DSB – Power Calculations How does AM compare with DSB? (Criteria for good modulation!) CS477: Analog and Digital Communications

  6. Power Calculations For DSB-SC or DSB: For DSB+C or AM: (100% modulation) CS477: Analog and Digital Communications

  7. Information signal is Tone Modulation For DSB-SC or DSB: For DSB+C or AM: CS477: Analog and Digital Communications

  8. Tone Modulation For DSB-SC or DSB: For DSB+C or AM: CS477: Analog and Digital Communications

  9. 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 CS477: Analog and Digital Communications

  10. USB LSB LSB USB Islands are not symmetric around SSB-AM First consider DSB-SC Pass it through an “SSB filter” CS477: Analog and Digital Communications

  11. (Transmission BW is twice the signal BW) SSB and DSB Comparison For DSB: For SSB: CS477: Analog and Digital Communications

  12. Information signal is Tone Modulation: SSB & DSB For DSB-SC or DSB: For USSB: For LSSB: CS477: Analog and Digital Communications

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