Modulation

• Modulation is a process of communication through which audio, video, image or text information is added an electrical or optical carrier signal to be transmitted over a telecommunication or electric medium.
• Like TV, radio, Internet etc. Here we need to transmit the information bearing signal from one place to another. To do this we need to strengthen the signal. So that the signal travels for long distances. This is what is called Modulation.





• Modulation enables the transfer of information on an electrical signal to a receiving device that demodulates the signal to extract the blended information.

Advantages of modulation

• With the help of modulation there is no mixing up of signals and the received signals are absolutely perfect.
• We can also decrease the height of the antenna.
• Modulation increase the range of communication.
• Allow the flexibility for adjusting the bandwidth.

Types of modulation

Analog modulation

• Analog modulation refers to the process of transferring an analog baseband (low frequency) signal, like an audio or TV signal over a higher frequency signal such as a radio frequency band.
• There are three types of analog modulation:
  1. Amplitude modulation
  2. Frequency modulation
  3. Phase modulation

Amplitude modulation

• In this the amplitude of carrier signal wave is varied in accordance with the modulating or message signal by keeping the phase and frequency of the signals constant.
• The carrier signal frequency would be greater than the modulating signal frequency.
• It is used for transmitting messages for long distances by the mankind.

Applications:

• AM is used in computer modem.
• AM is used in the aerospace industry is widespread. The radio contact between ground to air and also ground to ground use AM signals.

• Frequency modulation

  • The process of carrier signal frequency is varied according to the message signal or modulation signal frequency by keeping the amplitude constant is called frequency modulation.
  • Frequency modulation is used in audio frequencies to synthesize sound.
  
  
  
  
  Applications:
  • FM radio uses FM because of its larger bandwidth.
  
  
  
  
  
  • Satellite TV
  
  
  
  
  

  Phase modulation

  • In phase modulation the carrier signal varied in accordance with the phase of the modulating signal or message signal by keeping the frequency constant.
  • If the amplitude of message or modulating signal is huge then the phase shift will also be greater.
  • It is used in binary phase shift keying.
  
  
  
  
  Applications:
  • Phase modulation used in wireless technology like GSM, Wifi.
  • Phase modulation is also used in signal transmission system in army.

  Digital modulation

  • In this a message is converted from analog to digital message and then modulated by using a carrier wave.
  • For better quality and efficient communication digital modulation technique is used.
  • Example: PSK, ASK, FSK, QAM
  
  
  
  
  

  My notes