This set of Analog Communications Multiple Choice Questions & Answers (MCQs ) focuses on “Generation of DSBSC Waves”. 1. LCD uses. Page 1. Lecture Generation of DSBSC waves: balanced modulator, ring modulator. Page 2. Page 3. Double-sideband suppressed-carrier transmission (DSB-SC) is transmission in which In the DSB-SC modulation, unlike in AM, the wave carrier is not transmitted; .. A DSBSC generation and demodulation instrument is described as side.
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Double-sideband suppressed-carrier transmission DSB-SC is transmission in which frequencies produced by amplitude modulation AM are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level, ideally being completely suppressed.
DSB-SC transmission is a special case of double-sideband reduced dsbsd transmission.
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It is used for radio data systems. DSB-SC is generated by a mixer.
This consists of a message signal multiplied by a carrier signal. The mathematical representation of this process is shown below, where the product-to-sum trigonometric identity is used.
Double-sideband suppressed-carrier transmission – Wikipedia
Demodulation is done by multiplying the DSB-SC signal with the carrier signal just like the modulation process. This resultant signal is then passed through a low pass filter to produce genedation scaled version of original message signal.
Full depth modulation requires carrier re-insertion. The equation above shows that by multiplying the modulated signal by the carrier signal, the result is a scaled version of the original message signal plus a second term.
Once waces signal passes through a low pass filter, the higher frequency component is removed, leaving just the original message. This is best shown graphically.
Below is a message signal that one may wish to modulate onto a carrier, consisting of a couple of sinusoidal components with frequencies respectively Hz and Hz.
What is a DSBSC wave? Explain its generation using balanced modulator.
The name “suppressed carrier” comes about because the carrier signal component is suppressed—it does not appear in the output signal. This is apparent when the spectrum of the output signal is viewed. In the picture shown below we see four peaks, the two peaks below Hz are the lower sideband LSB and the two peaks above Hz are the upper sideband USBbut there is no peak at the Hz mark, which is the dzbsc of the suppressed carrier.