Angle Modulation DSB-SC Overview
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Questions and Answers

What is the primary difference between frequency modulation (FM) and phase modulation (PM)?

  • FM and PM are both forms of angle modulation, but they have no other relationship to each other.
  • In FM, the carrier's instantaneous phase is directly proportional to the input signal's amplitude, while in PM, the carrier's instantaneous frequency is directly proportional to the input signal's amplitude.
  • FM and PM are the same thing, just different names for the same modulation technique.
  • In FM, the carrier's instantaneous frequency is directly proportional to the input signal's amplitude, while in PM, the carrier's instantaneous phase is directly proportional to the input signal's amplitude. (correct)

    • What is the purpose of the low-pass filter in the coherent demodulation of a DSB-SC wave?

  • To remove the DSB-SC signal and obtain the original carrier signal.
  • To remove the original carrier signal and obtain a scaled version of the message signal. (correct)
  • To convert the DSB-SC signal back into a single-sideband (SSB) signal.
  • To amplify the message signal and remove any noise or interference.

    • Which of the following statements about the transmission efficiency of DSB-SC compared to traditional AM is correct?

  • DSB-SC has higher transmission efficiency because it does not require a separate carrier signal. (correct)
  • Transmission efficiency is not affected by the modulation technique, so DSB-SC and traditional AM have the same efficiency.
  • DSB-SC and traditional AM have the same transmission efficiency.
  • DSB-SC has lower transmission efficiency because it requires a separate carrier signal.

    • What is the purpose of multiplying the DSB-SC signal with a replica of the carrier signal during coherent demodulation?

    <p>To remove the original carrier signal and obtain a scaled version of the message signal.</p> Signup and view all the answers

    What is the primary advantage of using coherent demodulation to recover the message signal from a DSB-SC wave?

    <p>Coherent demodulation provides a more accurate and faithful reproduction of the original message signal.</p> Signup and view all the answers

    What is the main advantage of using Double Sideband Suppressed Carrier (DSB-SC) modulation?

    <p>Increased transmission efficiency by eliminating the carrier signal</p> Signup and view all the answers

    What is the mathematical expression for a DSB-SC wave?

    <p>$s(t) = m(t) \cdot c(t)$</p> Signup and view all the answers

    How is the bandwidth of a DSB-SC wave related to the bandwidth of the baseband signal?

    <p>The bandwidth of a DSB-SC wave is twice the bandwidth of the baseband signal</p> Signup and view all the answers

    What process is typically used to generate DSB-SC waves?

    <p>Angle modulation</p> Signup and view all the answers

    In the simplified equation for a DSB-SC wave, $s(t) = A_m c(t)$, what does $A_m$ represent?

    <p>The amplitude of the modulating signal</p> Signup and view all the answers

    Study Notes

    Angle Modulation DSB-SC

    Double sideband suppressed carrier (DSB-SC) is a method of transmitting digital or analog signals over a carrier wave without the need for a separate carrier signal. This approach eliminates wasted power in the carrier, thereby increasing the overall efficiency of the transmission. In DSB-SC, the carrier is suppressed, and the energy originally associated with the carrier is redistributed among the two sidebands, resulting in a more compact frequency spectrum.

    Equation of DSB-SC Wave

    Mathematically, the equation of a DSB-SC wave can be represented as the product of the modulating and carrier signals:

    [s(t) = m(t)c(t)]

    where (m(t)) represents the modulating signal and (c(t)) represents the carrier signal. When the carrier is suppressed, the equation simplifies to:

    [s(t) = A_mc(t)]

    where (A_m) and (c(t)) are constants related to the modulating signal amplitude and the carrier frequency, respectively.

    Bandwidth of DSB-SC Wave

    The bandwidth of a DSB-SC wave is determined by the largest frequency difference between any two nonzero frequency components in the waveform. Since DSB-SC waves consist of two sidebands symmetrically placed around the carrier frequency, their bandwidth is twice the bandwidth of the baseband signal.

    Generation

    DSB-SC waves are typically generated using a process known as angle modulation. One common form of angle modulation is frequency modulation (FM), where the carrier's instantaneous frequency is directly proportional to the input signal's amplitude. Another form is phase modulation (PM), in which the carrier's instantaneous phase is directly proportional to the input signal's amplitude.

    Demodulation

    Coherent demodulation is used to recover the original message signal from a DSB-SC wave. This involves multiplying the DSB-SC signal with a replica of the carrier signal, usually at the same phase as in the original transmission. The resultant signal is then passed through a low-pass filter to obtain a scaled version of the original message signal.

    Efficiency

    Compared to traditional AM, DSB-SC provides significant advantages in terms of transmission efficiency. Without the need for a separate carrier, all available power is utilized in conveying the desired information.

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    Description

    Learn about double sideband suppressed carrier (DSB-SC) modulation, its equation, bandwidth determination, generation using angle modulation, coherent demodulation, and transmission efficiency. Understand how DSB-SC optimizes power usage compared to traditional AM techniques.

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