Digital Modulation with introduction to ASK, FSK and PSK

Firstly, what do we mean by digital modulation? Typically the objective of a digital communication system is to transport digital data between two or more nodes. In radio communications this is usually achieved by adjusting a physical characteristic of a sinusoidal carrier, either the frequency, phase, amplitude. This is performed in real systems with a modulator at the transmitting end to impose the physical change to the carrier and a demodulator at the receiving end to detect the resultant modulation on reception. We begin our discussion by three basic types of digital modulations:
  • ASK [Amplitude Shift Keying]
  • FSK [Frequency Shift Keying]
  • PSK [Phase Shift Keying]
All of these techniques vary the parameter of a sinosoid to represent the information we wish to transmit.
A sinusoid has three parameters that can be varied, these are amplitude ,phase and frequency.

  • In FSK we change the frequency in response to information. One particular frequency for ‘1’ and another frequency for ‘0’.

  • In PSK, we change the phase of carrier signal to indicate information.

  • In ASK amplitude of carrier is changed in response to information n all else is kept fixed. Bit ‘1’ is transmitted by a carrier of one particular amplitude.To transmit ‘0’ we change the amplitude

Posted by Sadaf Dilshad Khan on 23:56. Filed under , , , , . You can follow any responses to this entry through the RSS 2.0. Feel free to leave a response


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