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Analog Communication: Amplitude Modulation Systems
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Analog Communication: Amplitude Modulation Systems

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Questions and Answers

What is the ratio of total side band power to the total power in the modulated wave called?

  • Power spectral density
  • Modulation index
  • Sideband power ratio
  • Efficiency of AM system (correct)
  • What type of device is a square law modulator?

  • Active device
  • Passive device
  • Non-linear device (correct)
  • Linear device
  • What is the frequency of the dc component in the output of a square law modulator?

  • fc
  • 2fc
  • W
  • 0 (correct)
  • What is the purpose of a band pass filter in a switching modulator?

    <p>To separate the AM signal centered at fc</p> Signup and view all the answers

    What is the output of a switching modulator when c(t) is positive?

    <p>v2 = v1</p> Signup and view all the answers

    What is the process of recovering the original information signal from the modulated wave called?

    <p>Demodulation</p> Signup and view all the answers

    What is the expression for the total input to a square law device in an AM wave?

    <p>Ac cos(2Ï€fct) + m(t)</p> Signup and view all the answers

    What is the frequency range of the information signal in an AM wave?

    <p>0 to W</p> Signup and view all the answers

    What is the frequency range for AM in radio broadcasting?

    <p>535 kHz – 1600 kHz</p> Signup and view all the answers

    What is the bandwidth of an AM wave?

    <p>10 kHz</p> Signup and view all the answers

    What is the equation for an amplitude modulated signal?

    <p>s(t) = Ac [1 + kam(t)] cos(ωct)</p> Signup and view all the answers

    What is the significance of 'ka' in amplitude modulation?

    <p>amplitude sensitivity</p> Signup and view all the answers

    What is the condition for the carrier frequency in amplitude modulation?

    <p>fc &gt;&gt; W</p> Signup and view all the answers

    What is the name of the modulation scheme where the amplitude of the carrier is varied linearly by the modulating signal?

    <p>Conventional Amplitude Modulation</p> Signup and view all the answers

    What is the modulation index in amplitude modulation?

    <p>kam(t)</p> Signup and view all the answers

    What is the Fourier Transform of the amplitude modulated signal?

    <p>S(ω) = π Ac/2 (δ(ω − ωc) + δ(ω + ωc)) + kaAc/ 2 (M(ω − ωc) + M(ω + ωc))</p> Signup and view all the answers

    Study Notes

    Amplitude Modulation (AM)

    • Amplitude Modulation is the process of changing the amplitude of a high-frequency carrier signal in accordance with the amplitude of the modulating signal (information).
    • The carrier amplitude is varied linearly by the modulating signal, which usually consists of a range of audio frequencies.
    • The frequency of the carrier is not affected.

    Applications of AM

    • Radio broadcasting
    • TV pictures (video)
    • Facsimile transmission

    Frequency Range and Bandwidth of AM

    • Frequency range: 535 kHz – 1600 kHz
    • Bandwidth: 10 kHz

    Forms of Amplitude Modulation

    • Conventional Amplitude Modulation (Full AM or Double Sideband Large carrier modulation (DSBLC) / Double Sideband Full Carrier (DSBFC))
    • Double Sideband Suppressed carrier (DSBSC) modulation
    • Single Sideband (SSB) modulation
    • Vestigial Sideband (VSB) modulation

    Time and Frequency Domain Description

    • Amplitude modulated signal: s(t) = Ac [1 + kam(t)] cos(ωct)
    • Fourier Transform: S(ω) = Ï€ Ac/2 (δ(ω − ωc) + δ(ω + ωc)) + kaAc/ 2 (M(ω − ωc) + M(ω + ωc))

    Single Tone Modulation

    • Modulating wave: m(t) = Acm cos(ωmt)
    • Amplitude modulated signal: s(t) = Ac [1 + kam cos(ωmt)] cos(ωct)

    Power Relations in AM Waves

    • Ratio of total sideband power to total power in the modulated wave is called the efficiency of the AM system

    Generation of AM Waves

    • Two basic amplitude modulation principles:
      • Square law modulation
      • Switching modulator

    Square Law Modulator

    • Output of a non-linear device is not directly proportional to the input throughout the operation
    • Input-Output relation: y(t) = a1x(t) + a2x^2(t)
    • Square law device output: V0 = Vdc + Vm cos(ωmt)

    Switching Modulator

    • Total input for the diode: v1 = Ac cos(ωct) + m(t)
    • When c(t) is positive, v2=v1, and when c(t) is negative, v2=0
    • Switching response of the diode: v2 = v1 * s(t)

    Detection of AM Waves

    • Demodulation is the process of recovering the original message signal from the amplitude-modulated wave.

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    Quiz Team

    Description

    Learn about amplitude modulation systems, including the generation and detection of AM waves. Understand the process of amplitude modulation and its applications.

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