Modulation

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	To oppose or discuss a nomination, please go to CZ:Proposed for deletion and follow the instructions. For the monthly nomination lists, see Category:Articles for deletion. In electronics and physics, modulation refers to methods of communications that change the characteristics of a periodic waveform, such that the changes represent information to be transmitted over the electromagnetic]] carrier wave]] of the basic waveform. While the term is most often used with radio frequency carrier waves, it can apply to sound wave]]s as well, such as when a basic steady tone from a musical instrument is varied to express a musical theme. There are several basic forms of modulation, which can be divided into basic analog]], signal-processed analog]], and digital]]. The basic analog types impose the information change by: Amplitude modulation]] (AM): Varying the strength of the signal in proportion to the information carried. Pure amplitude modulation transmits a carrier, plus a high and low sideband as an effect of superheterodyne|heterodyning]] Double sideband suppressed carrier: the carrier wave, which does not carry information, is suppressed and both identical sidebands transmitted. Rarely used. Single sideband (SSB): Only one of the sidebands is transmitted; the carrier and other sideband is suppressed. Very common technique for non-entertainment communications radio due to its power efficiency. Frequency modulation]]:Changing the frequency (i.e., the time between peaks of the basic frequency) Phase modulation]]: Shifting the phase of the signal by changing the relative starting point of individual waves with respect to a reference carrier wave. Digital modulation is somewhat more indirect than the analog methods. In digital modulation, the information is first encoded into a set of nonperiodic pulse, such as zero voltage to convey a zero bit and a nonzero voltage to convey a nonzero bit. The pulses are then used to amplitude, frequency, or phase modulate a carrier wave.