Phase modulation (PM) is a form of modulation which represents information as variations in the instantaneous phase of a carrier wave. In telecommunications, modulation is the process of varying a periodic waveform, i. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... A carrier wave, or carrier is a waveform (usually sinusoidal) that is modulated (modified) to represent the information to be transmitted. ...

Unlike its more popular counterpart, frequency modulation (FM), PM is not very widely used (except perhaps in the inappropriately named FM synthesis for musical instruments, introduced by Yamaha around 1982.) This is because it tends to require more complex receiving hardware and there can be ambiguity problems with determining whether, for example, the signal has 0° phase or 180° phase. Frequency modulation (FM) is a form of modulation which represents information as variations in the instantaneous frequency of a carrier wave. ... Frequency modulation synthesis (or FM synthesis) is a form of audio synthesis where the timbre of a simple waveform is changed by frequency modulating it with a modulating frequency that is also in the audio range, resulting in a more complex waveform and a different-sounding tone. ... A degree (in full, a degree of arc, arc degree, or arcdegree), usually symbolized °, is a measurement of plane angle, representing 1／360 of a full rotation. ...

Theory

An example of phase modulation. The top diagram shows the modulating signal superimposed on the carrier wave. The bottom diagram shows the resulting phase-modulated signal.

Suppose that the signal to be sent, the modulating signal with frequency ω_m and phase φ_m, is Image File history File links Phase modulation example. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ...

,

and the carrier onto which the signal is to be modulated is

.

Then the modulated signal,

,

which shows how m(t) modulates the phase. Clearly, it could also be viewed as a change to the frequency of the carrier signal, so PM can be considered a special case of FM where the carrier frequency modulation is the time derivative of the modulating signal. The abbreviations FM, Fm, and fm may refer to: Electrical engineering Frequency modulation (FM) and its most common applications: FM broadcasting, used primarily to broadcast music and speech at VHF frequencies FM synthesis, a sound-generation technique popularized by early digital synthesizers Science Femtometre (fm), an SI measure of length... In mathematics, a derivative is the rate of change of a quantity. ...

The spectral behaviour of Phase-Modulation (PM) is difficult to derive, but the mathematics reveals that there are two regions of particular interest: In applied mathematics and physics, the spectral density is a general concept applied to a signal which may have any physical dimensions or none at all. ...

• For small amplitude signals, PM is similar to amplitude modulation (AM) and exhibits its unfortunate doubling of baseband bandwidth and poor efficiency.
• For a single large sinusoidal signal, PM is similar to FM, and its bandwidth is approximately

Hz,

where f_M = ω_m / 2π and h is the modulation index defined below. This is also known as Carson's Rule for PM.

Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation, that is, magnitude of the maximum disturbance in the medium during one wave cycle. ... [[Amplitude modulation]] (AM) is a technique used in electronic communication, most commonly for transmitting information via a carrier wave wirelessly. ... Baseband is an adjective that describes signals and systems whose range of frequencies is measured from 0 to a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies starting at 0. ... This article or section does not cite its references or sources. ... In mathematics, the trigonometric functions are functions of an angle, important when studying triangles and modeling periodic phenomena. ... The hertz (symbol: Hz) is the SI unit of frequency. ... In telecommunication, Carsons bandwidth rule defines the approximate bandwidth requirements of communications system components for a carrier signal that is frequency modulated by a continuous or broad spectrum of frequencies rather than a single frequency. ...

Modulation index

As with other modulation indices, in PM this quantity indicates by how much the modulated variable varies around its unmodulated level. For PM, it relates to the variations in the phase of the carrier signal: The modulation index (mf) is defined as the ratio of the frequency deviation σ to the modulating signal frequency fi, i. ...

h = Δθ,

where Δθ is the peak phase deviation. Compare to the modulation index for frequency modulation. Frequency modulation (FM) is a form of modulation which represents information as variations in the instantaneous frequency of a carrier wave. ...

See also

• Modulation for a list of other modulation techniques
• Phase-shift keying (PSK), the digital version of PM
• Electro-optic_modulator for Pockel's Effect phase modulation for applying sidebands to a monochromatic wave