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Home > Modulation

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, includes BPSK, QPSK, etc.)
• 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
• Trellis modulation
• Adaptive modulationAdaptive Modulation is a transmission scheme in digital communications where the transmitter adapts its transmission mode in accordance with the channel. Depending on the severity of the channel, the transmitter could be adapting one or more of the follow
• Sigma-delta modulation (∑Δ)

When OFDM is used in conjunction with channel codingIn digital telecommunications, channel coding is a pre-transmission mapping applied to a digital signal or data file, usually designed to make error-correction possible. Error correction is implemented by using more digits ( bits in case of a binary chann techniques, it is described as ' Coded orthogonal frequency division modulation' (COFDM).

Pulse modulation techniques include:

• Pulse-code modulationPulse-code modulation PCM is a modulation technique. It is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals. Every sample is quantized to a series of symbols in a digital code, which (PCM)
• Pulse-width modulationPulse-width modulation is a way to represent data over a communications channel. With pulse-width modulation, the value of a sample of data is represented by the length of a pulse. Pulses of various lengths (the information itself) will be sent at regular (PWM)
• Pulse-amplitude modulationPulse-amplitude modulation acronym PAM is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Example: A two bit modulator (4-PAM) will take two bits at a time and will map the signal amplitu (PAM)
• Pulse-position modulationPulse-position modulation is a form of signal modulation in which the message information is encoded in the temporal spacings between a sequence of signal pulses. This method is not used very frequently, because other methods are usually more suitable for (PPM)
• Pulse-density modulationPulse-density modulation or PDM is a form of modulation used to represent an analog signal in the digital domain. In a PDM signal, specific amplitude values are not encoded into pulses as they would be in PCM or PWM. Instead it is the relative density of (PDM)

Where the signal is a simple low speed on-off indication, as in morse code or radioteletype ( RTTY) transmission, modulation is often known as 'keying' as in the terms

• Frequency-shift keying (FSK) see Frequency modulation
• Phase-shift keying (PSK) see Phase modulation
• Gaussian Minimum Shift Keying (GMSK)

RTTY can also be regarded as a simple kind of pulse code 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:

• Types of radio emissions
• Communications channel
• Channel coding
• Telecommunication
• Modem
• RF modulator
• Codec

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Topics: Modulation Keying Techniques Frequency Channel Signal Amplitude...

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ModulationFor the musical use of "modulation", see modulation (music . 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 techn Modulation factorModulation factor In amplitude modulation, the ratio of the peak variation actually used, to the maximum design variation in a given type of modulation. Note: In conventional amplitude modulation, the maximum design variation is considered that for which Modulation rateIn telecommunication, the term modulation rate has the following meanings: 1. The rate at which a carrier is varied to represent the information in a digital signal. Modulation rate and information transfer rate are not necessarily the same. For modulated Modulation (music)In music, modulation is most commonly the act or process of changing from one key ( tonic, or tonal center) to another, also known as a key change''. This may or may not be accompanied by a change in key signature. Modulations articulate or create the str Modulation indexThe modulation index m''f) is defined as the ratio of the frequency deviation σ to the modulating signal frequency fi i. mf σ fi''.