In music, the term "modulation" means a key change. This article is about the concept of signal modulation in communications engineering.
Modulation describes a range of techniques for encoding information on a carrier signal, typically a sine-wave signal. A device that performs modulation is known as a modulator.
Modulation techniques include:
- Amplitude modulation (AM)
- Phase modulation (PM)
- Frequency modulation (FM)
- Single-sideband modulation (SSB)
- Vestigial-sideband modulation (VSB, or VSB-AM)
- Quadrature amplitude modulation (QAM)
- Orthogonal frequency division modulation (OFDM), also known as 'Discrete multitone modulation' (DMT)
- Wavelet modulation
- Ring modulation
Pulse modulation techniques include:
- Pulse-code modulation (PCM)
- Pulse-width modulation (PWM)
- Pulse-amplitude modulation (PAM)
- Pulse-position modulation (PPM)
- Frequency-shift keying (FSK) see Frequency modulation
- Phase-shift keying (PSK) see Phase modulation
Where Morse code is used to turn the carrier wave on and off, the term used is not 'amplitude keying', but 'continuous wave' (CW) operation.
Modulation is frequently used in conjunction with various channel access methods.
See also: