Editing Signal modulation (section)

==Analog modulation methods{{anchor|Analog}}==
[[File:Amfm3-en-de.gif|thumb|right|200px|A low-frequency message signal (top) may be carried by an AM or FM radio wave.]]
[[File:Waterfall AM.jpg|thumb|[[Waterfall plot]] of a 146.52&nbsp;MHz radio carrier, with amplitude modulation by a 1,000&nbsp;Hz sinusoid. Two strong sidebands at + and - 1&nbsp;kHz from the carrier frequency are shown.]]
[[File:Waterfall FM.jpg|thumb| A carrier, frequency modulated by a 1,000&nbsp;Hz sinusoid. The [[modulation index]] has been adjusted to around 2.4, so the carrier frequency has small amplitude. Several strong sidebands are apparent; in principle an infinite number are produced in FM but the higher-order sidebands are of negligible magnitude.]]

In [[analog signal|analog]] modulation, the modulation is applied continuously in response to the analog information signal. Common analog modulation techniques include:
* [[Amplitude modulation]] (AM) (here the amplitude of the carrier signal is varied in accordance with the instantaneous amplitude of the modulating signal)
** Double-sideband modulation (DSB)
*** Double-sideband modulation with carrier (DSB-WC) (used on the AM radio broadcasting band)
*** [[Double-sideband suppressed-carrier transmission]] (DSB-SC)
*** [[Double-sideband reduced carrier transmission]] (DSB-RC)
** [[Single-sideband modulation]] (SSB, or SSB-AM)
*** Single-sideband modulation with carrier (SSB-WC)
*** Single-sideband modulation suppressed carrier modulation (SSB-SC)
** [[Vestigial sideband modulation]] (VSB, or VSB-AM)
** [[Quadrature amplitude modulation]] (QAM)
* [[Angle modulation]], which is approximately [[constant envelope]]
** [[Frequency modulation]] (FM) (here the frequency of the carrier signal is varied in accordance with the instantaneous amplitude of the modulating signal)
** [[Phase modulation]] (PM) (here the phase shift of the carrier signal is varied in accordance with the instantaneous amplitude of the modulating signal)
** Transpositional Modulation (TM), in which the waveform inflection is modified resulting in a signal where each quarter cycle is transposed in the modulation process. TM is a pseudo-analog modulation (AM). Where an AM carrier also carries a phase variable phase f(ǿ). TM is f(AM,ǿ)
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