What Is Single SideBand (SSB) Systems And Why To Use SSB :
The purpose of this article is to explain that What Is Single SideBand i.e. SSB or what is the purpose to use SSB rather than DSBFC (Double SideBand Full Carrier).
What Is Single SideBand Systems:
Conventional AM Double sideband systems have two inherent disadvantages. First ,with conventional AM carrier power constitutes two third or more of total transmitted power which is major drawback because information is carried in two identical side bands and not in carrier second , is that with double side bands both sidebands carry same information .Therefore, transmitting both sidebands is redundant.
What Is Single SideBand Suppressed Carrier (SSBSC) Systems:-
It is a form of amplitude modulation in which the carrier is totally suppressed and one of the sideband removed. so it requires half bandwidth than the conventional DSBFC (Double Sideband Full Carrier) and less transmitted power.
Generation Of Single Sideband Suppressed Carrier (SSBSC):
Modulating signal = sin(wmt) fed directly to balanced modulator 1 and shifted 900 = cos(wmt) fed to balanced modulator 2.
Lower carrier frequency = sin(wct) is fed directly to balanced modulator 1 and shifted 900 = coswct fed to balanced modulator 2.
Outputs are :Output from balanced modulator 1 = (sinwmt) (sinwct) =
1/2cos(wc-wm)t – 1/2cos(wc+wm)t
Output from balanced modulator 2 =(coswmt)(coswct)
And the output from linear summer is
Upper sideband cancelled and we get lower sideband at output.
Advantages of single sideband transmission:-
1. Power conservation:-
Due to the transmission of only one sideband with its carrier suppressed so much less of total power is used to transmit good quality signal to receiver section. Hence, a lot of power remains unused in this transmission so it is better than DSBFC (Double SideBand Full Carrier)
2. Bandwidth conservation:-
Only one sideband is transmitted so it require one third as much bandwidth as needed in conventional AM transmission i.e. bandwidth factor is reduced by more than factor of 2 than DSBFC (Double Sideband Full Carrier) transmission. So Bandwidth will Saved Moreover
So, Noise will also reduced and S/N ratio increases.
3. Noise Reduction:-
Because a single side band requires half bandwidth, the thermal noise is also reduced to half
Using phase shift method at output we get single sideband and suppressed carrier. Now, as a result much less total transmitted power is necessary. Bandwidth requires half as much bandwidth as conventional AMDSB-transmission. This is especially required with an already overcrowded radio-frequency spectrum.