5. Key Digital Modulation Techniques

Digital modulation techniques are used to impress binary data (1s and 0s) onto a high-frequency carrier signal for transmission. Each technique alters a different property of the carrier wave—its amplitude, frequency, or phase—to represent the digital information.

• Amplitude Shift Keying (ASK)
  • Definition: ASK is a technique where the binary data is represented by variations in the signal’s amplitude.
  • How it works: A binary LOW (0) input results in a zero-level amplitude (no signal), while a binary HIGH (1) input results in the carrier wave being transmitted at its normal amplitude.
• Frequency Shift Keying (FSK)
  • Definition: FSK is a technique where the carrier signal’s frequency varies based on the digital input.
  • How it works: A binary LOW (0) input results in a low-frequency output (called the “Space” frequency), while a binary HIGH (1) input results in a high-frequency output (called the “Mark” frequency).
• Phase Shift Keying (PSK)
  • Definition: PSK is a technique in which the phase of the carrier signal is changed to represent the digital data.
  • How it works: A common type is Binary Phase Shift Keying (BPSK), where the carrier signal takes on two distinct phase reversals. For example, a 0 might be represented by a 0° phase, and a 1 might be represented by a 180° phase reversal.

Summary of Digital Techniques

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By understanding these fundamental concepts, from the nature of signals to the methods of modulation, you have built a strong foundation in communication principles.

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