Digital Modulation

Target:

Make the signal suitable for transmission in channel.

Usual Methods:

Digital Data

 ASK (Amplitude-Shift Keying);  FSK (Frequency-Shift Keying);  PSK (Phase-Shift Keying);

Analog Data

 AM (Amplitude Modulation);  PM (Phase Modulation);  FM (Frequency Modulation);

1. 2ASK

 Spread digital signal through the amplitude of a carrier wave, or on-off-keying.

• Modulate :
  • 1. Analog Modulation.
  • 2. Keying

• Demodulate :
  • 1. Noncoherent.

2. 2FSK

 Spread digital data through the frequency of a carrier wave.

• Modulate:
  • Keying
• Demodulate :

3. 2PSK

 Spread digital signal through the phase of a carrier wave.

• Modulate :
  • 1. Analog Modulation.
  • 2. Keying.
       
• Demodulate :
  • Coherent
    

4.2DPSK(Differential-Phase-Shift Keying)

  Spread digital signal through changing the phase of the carrier wave.   Phase difference: 0 –> stand “1”   ; π –> stand “0”   Or reverse.

• Modulate :
  • 1. Keying.
• Demodulation :