Definition:
Modulation is the process of varying a carrier signal’s properties (amplitude, frequency, or phase) to encode information for transmission.

Working Principle:

• Analog Modulation:
  • AM (Amplitude Modulation): Varies the carrier’s amplitude.
  • FM (Frequency Modulation): Varies the carrier’s frequency.
  • PM (Phase Modulation): Varies the carrier’s phase.
• Digital Modulation:
  • ASK (Amplitude Shift Keying), FSK (Frequency Shift Keying), PSK (Phase Shift Keying).
  • Advanced schemes like QAM (Quadrature Amplitude Modulation) combine amplitude and phase changes.

Functions:

• Allows efficient signal propagation over long distances.
• Reduces interference by shifting signals to different frequency bands.
• Enables multiplexing (multiple signals over one channel).

Use Cases:

• Broadcasting: AM/FM radio, TV signals.
• Telecom: 4G/5G (QAM, OFDM), Wi-Fi (DSSS, OFDM).
• Space Communication: Deep-space probes use PSK for reliable data transfer.

Example : AM, FM, QPSK, QAM