Sideband Modulation - Principles of Communication

What is Sideband Modulation?

In the procedure of Amplitude Modulation or Phase Modulation, the modulated wave comprises of the carrier wave and two sidebands. The modulated signal has the information in the whole band except at the carrier frequency.

Sideband

A Sideband is a band of frequencies, comprising power, which is the lower and higher frequencies of the carrier frequency. Both the sidebands comprise the same information. The demonstration of amplitude modulated wave in the frequency domain is as shown in the resulting figure.


sideband (1)


Both the sidebands in the image contain the same information. The transmission of such a signal which contains a carrier along with two sidebands, can be termed as Double Sideband Full Carrier system, or simply DSB-FC. It is plotted as shown in the resulting figure.

dsbfc_system

On the other hand, such a transmission is ineffective. Two-thirds of the power is being misused in the carrier, which carries no information.
If this carrier is blocked and the power saved is distributed to the two sidebands, such a procedure is called as Double Sideband Suppressed Carrier system, or simply DSBSC. It is plotted as shown in the following figure.

dsbsc_system


Currently, we get an idea that, as the two sidebands carry the same statistics twice, why can’t we suppress one sideband. Yes, this is possible.
The procedure of suppressing one of the sidebands, along with the carrier and transmitting a single sideband is called as Single Sideband Suppressed Carrier system, or simply SSB-SC or SSB. It is plotted as shown in the resulting figure.

ssbsc_system


This SSB-SC or SSB system, which communicates a single sideband, has high power, as the power chosen for both the carrier and the other sideband is utilized in transmitting this Single Sideband (SSB).

Therefore, the modulation done using this SSB technique is called as SSB Modulation.

Sideband Modulation − Advantages


The advantages of SSB modulation are −

  • Bandwidth or spectrum space occupied is lesser than AM and DSB signals.
  • Transmission of more number of signals is allowed.
  • Power is saved.
  • High power signal can be transmitted.
  • Less amount of noise is present.
  • Signal fading is less likely to occur.

Sideband Modulation − Disadvantages

The disadvantages of SSB modulation are −

  • The generation and detection of SSB signal is a complex process.
  • Quality of the signal gets affected unless the SSB transmitter and receiver have an excellent frequency stability.

Sideband Modulation − Applications

The applications of SSB modulation are −

  • For power saving requirements and low bandwidth requirements.
  • In land, air, and maritime mobile communications.
  • In point-to-point communications.
  • In radio communications.
  • In television, telemetry, and radar communications.
  • In military communications, such as amateur radio, etc.

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