DSB is not widely used because the signal is difficult to demodulate recover at

Dsb is not widely used because the signal is

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DSB is not widely used because the signal is difficult to demodulate (recover) at the receiver.
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cos 2π(f c +f m )t ] DSB-SC consist of the product of the modulating signal and carrier signal. E DSB-SC = E c E m = E c sin (2πf c t) E m sin (2πf m t) using trigonometry identity, E DSB-SC = E c E m [ cos 2π(f c -f m )t - The signal consist of two waveform with sideband frequencies (no carrier). If no modulating signal (E m =0) there will be no modulated signal produced. 1 2 1 2
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Figure 13: A frequency-domain display of DSB signal.
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One sideband is all that is necessary to convey information in a signal. A single-sideband suppressed carrier (SSSC) signal is generated by suppressing the carrier and one sideband.
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SSB signals offer four major benefits: 1. Spectrum space is conserved and allows more signals to be transmitted in the same frequency range. 2. All power is channeled into a single sideband. This produces a stronger signal that will carry farther and will be more reliably received at greater distances. 3. Occupied bandwidth space is narrower and noise in the signal is reduced. 4. There is less selective fading over long distances.
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Signal Side Band Power Considerations In SSB, the transmitter output is expressed in terms of peak envelope power (PEP), the maximum power produced on voice amplitude peaks. PEP is given by PEP = V rms2 /R Example : A voice signal produces 360 V peak-to- peak signal across 50 Ω load. PEP = = 324 W [(360/2)0.707] 2 50
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Disadvantages of DSB and SSB Single and double-sideband are not widely used because the signals are difficult to recover (i.e. demodulate) at the receiver. A low power, pilot carrier is sometimes transmitted along with sidebands in order to more easily recover the signal at the receiver.
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Applications of DSB and SSB Two-way communication in military and radio amateurs (ham radio). Transmit two-channel stereo signal. Transmit color information for TV picture. A vestigial sideband signal (VSB) is produced by partially suppressing the lower sideband. This kind of signal is used in TV transmission.
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