Explain the scheme of generating and demodulating of vsb signal
Answers
Describe Vestigial Sideband Transmission (VSB) . Applications of Vestigial Siddeband TransmissionAMPLITUDE MODULATION BY SASMITA DECEMBER 30, 2015
Vestigial Sideband Transmission
The exact frequency response requirements on the side band filter in SSB-SC system can be relaxed by allowing a part of the unwanted side band called vestige to appear in the output of the modulator.
Due to this, the design of the side band filter is simplified to a great extent .
But the bandwidth of the system is increased slightly .
To generate a VSB signal, we have to first generate a DSB-SC signal and then pass it through a side band filter as shown in fig. 1 . This filter will pass the wanted side band as it is along with a part of unwanted side band .
block diagram of VSB transmitter
Fig.1 : VSB Transmitter
Frequency Domain Description
Frequency Spectrum
The spectrum of VSB is as shown in fig. 2 .
spectrum of message signal
(a) Spectrum of message signal
Spectrum of VSB signal
(b) Spectrum of VSB Signal
Fig. 2
The spectrum of message signal x(t) has also been shown .
In the frequency spectrum, it is assumed that the upper side band is transmitted as it is and the lower side band is modified into vestigial side band .
Transmission Bandwidth
From fig. 2 (b), it is evident that the transmission bandwidth of the VSB modulated wave is given by :
bandwidth of VSB
Where fm = Message bandwidth
fv = Width of the vestigial side band