Baseband Signal :
If a signal consisting of lower frequencies (up to 10 KHZ) then it is known as Baseband signal.
Ex : Voice,Audio,Video...etc.
Baseband signals can not transmitted directly through an antenna.
Passband signals :
If a signal consisting of significant higher frequencies (more then 100 KHZ) known as Bandpass or Passband signal. It can transmit directly through an antenna.
Modulation :
By Modulation the signal is translated from lower frequency (LF) to higher frequency (HF) region or Baseband signal to Passband signal.
Carrier Signal :
The signal that is used in modulation is known as carrier signal.
Message Signal :
The signal that is used in modulating the carrier signal is known as message signal or data signal.
Types of Modulation :
Amplitude Modulation :
In this modulation the amplitude of the carrier signal is modulated or changed in proportional to the message signal.
Frequency Modulation :
In this modulation the frequency of the carrier signal is modulated or changed in proportional to the message signal.
Advantages Of Modulation :
- Reduction in the height of antenna.
- Avoids mixing of signals.
- Increases the range of communication.
- Multiplexing is possible.