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Questions and Answers
What is the primary difference between frequency modulation (FM) and phase modulation (PM)?
What is the purpose of the low-pass filter in the coherent demodulation of a DSB-SC wave?
Which of the following statements about the transmission efficiency of DSB-SC compared to traditional AM is correct?
What is the purpose of multiplying the DSB-SC signal with a replica of the carrier signal during coherent demodulation?
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What is the primary advantage of using coherent demodulation to recover the message signal from a DSB-SC wave?
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What is the main advantage of using Double Sideband Suppressed Carrier (DSB-SC) modulation?
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What is the mathematical expression for a DSB-SC wave?
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How is the bandwidth of a DSB-SC wave related to the bandwidth of the baseband signal?
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What process is typically used to generate DSB-SC waves?
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In the simplified equation for a DSB-SC wave, $s(t) = A_m c(t)$, what does $A_m$ represent?
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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.
