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Topic: Modulation

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In the News (Fri 24 May 19)

  modulation, in communications. The Columbia Encyclopedia, Sixth Edition. 2001-07
When the carrier is thus modulated, a fraction of the power is converted to sidebands extending above and below the carrier frequency by an amount equal to the highest modulating frequency.
In frequency modulation (FM), the frequency of the carrier wave is varied in such a way that the change in frequency at any instant is proportional to another signal that varies with time.
The modulation might vary the amplitude (PAM or pulse amplitude modulation), the duration (PDM or pulse duration modulation), or the presence of the pulses (PCM or pulse code modulation).
www.bartleby.com /65/mo/modulat1.html   (690 words)

  Nikon MicroscopyU: Modulation Transfer Function
Modulation of the output signal, the intensity of light waves forming an image of the specimen, corresponds to the formation of image contrast in microscopy.
Modulation is typically less in the image than in the specimen and there is often a slight phase displacement of the image relative to the specimen.
The modulation transfer function is also related to the point spread function, which is the image of a point source of light (commonly referred to as the Airy disk) from the specimen projected by the microscope objective onto the intermediate image plane.
www.microscopyu.com /articles/optics/mtfintro.html   (4055 words)

Modulation is the process where a Radio Frequency or Light Wave's amplitude, frequency, or phase is changed in order to transmit intelligence.
In Pulse Amplitude Modulation, a pulse is generated with an amplitude corresponding to that of the modulating waveform.
Also known as Pulse Time Modulation, PPM is a scheme where the pulses of equal amplitude are generated at a rate controlled by the modulating signal's amplitude.
telecom.tbi.net /mod1.html   (797 words)

This type of modulation is often used to create a sudden change of mood via it's sudden change of tonality.
By preceding a modulation with a harmony that functions both in the old and new keys, the change of tonic becomes smoother and less abrupt.
In works that are not in a chorale style, composers often modulate through the use of a common tone in the melody.
www.smu.edu /totw/modulate.htm   (801 words)

  Modulation - Wikipedia, the free encyclopedia
Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information.
A device that performs modulation is known as a modulator and a device that performs the inverse operation of demodulation is known as a demodulator.
In analog modulation, the change is applied continuously in response to the data signal.
en.wikipedia.org /wiki/Modulation   (801 words)

 Modulation (music) - Wikipedia, the free encyclopedia
Phrase (also called direct or abrupt) modulation is a modulation in which one phrase ends with a cadence in the original key, and begins the next phrase in the destination key without any transition material linking the two keys.
A sequence does not have to modulate; a modulating sequence is known as a rosalia.
Modulation may also occur from a single tonality to a polytonality, often by beginning with a duplicated tonic chord and modulating the chords in contrary motion until the desired polytonality is reached.
en.wikipedia.org /wiki/Modulation_(music)   (1195 words)

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 is frequently used in conjunction with various channel access methods.
www.ebroadcast.com.au /lookup/encyclopedia/mo/Modulator.html   (177 words)

The modulating signal is shown in A. The dashed-line waveforem, in B, is the curve of the reference vector and the solid-line waveform is the carrier.
In amplitude modulation, the amplitude of the carrier is varied in proportion to the amplitude of the modulating wave.
The percentage of modulation of an a-m wave is the percentage ratio of the peak-to-peak amplitude of the modulating voltage to the peak-to-peak amplitude of the carrier.
www.geocities.com /SoHo/Study/8903/fmod1.html   (4685 words)

 Privateline.com: Digital Wireless Basics: Modulation
Frequency modulation, such as analog cell phones use, provides better sound but it needs more bandwidth to achieve that quality and is technically more complex to produce.
Amplitude modulation means a carrier wave is modulated in proportion to the strength of a signal.
Phase modulation is strictly for digital working and is closely related to F.M. Phase in fact enjoys the same capture effect as F.M. First, a note.
www.privateline.com /PCS/modulation.htm   (2492 words)

 Digital Modulation :: Modulation (Communications Toolbox)
To modulate a signal using digital modulation with an alphabet having M symbols, start with a real message signal whose values are integers from 0 to M-1.
This is due to the modulation functions using symbol values instead of the symbol positions.
Modulation is often followed by pulse shaping, and demodulation is often preceded by a filtering or an integrate-and-dump operation.
www.mathworks.com /access/helpdesk/help/toolbox/comm/ug/a1041263435.html   (1179 words)

 Modulation - DSPWiki
Modulation is defined as varying one signal according to changes in a second signal.
In AM Double Sideband Modulation, the carrier is not suppressed, so this type of modulation is useful for radio applications where a receiver has to lock in on the carrier signal in order to tune in a radio station.
When the modulator signal is set to sub-audio frequencies, the increase in its amplitude is heard as an increase in the range of the vibrato caused by the modulator.
www.gersic.com /dspwiki/index.php?title=Modulation   (2378 words)

 Part16: Modulation
This section briefly discusses modulation, the process a modem uses to convert the digital data into analogue tones which are sent over the dial up connection.
Modulation is the mechanism that a modem uses to convert digital signals to analogue signals for sending across a telephone connection.
The three different type of modulation are amplitude, frequency and phase, although phase amplitude modulation is a combined technique of different phase and relative signal levels that offers the greatest speed of the methods discussed above.
physinfo.ulb.ac.be /cit_courseware/datacomm/dc_016.htm   (674 words)

 Frequency modulation Summary
With amplitude modulation, the amplitude (the distance between the "peak" and " trough") of the radio wave "carrier" is modulated to match the frequency of an audio signal.
(Contrast this with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant.) In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal.
Note that frequency modulation can be regarded as a special case of phase modulation where the carrier phase modulation is the time integral of the FM modulating signal.
www.bookrags.com /Frequency_modulation   (1511 words)

 What is modulation? - a definition from Whatis.com
Modulation can be applied to direct current (mainly by turning it on and off), to alternating current, and to optical signals.
Optical signals are modulated by applying an electromagnetic current to vary the intensity of a laser beam.
In a modem, the modulation processinvolves the conversion of the digital computer signals (high andlow, or logic 1 and 0 states) to analog audio-frequency (AF)tones.
searchnetworking.techtarget.com /sDefinition/0,,sid7_gci212586,00.html   (695 words)

 Wikipedia: Modulation - Wikipedia, the free encyclopedia   (Site not responding. Last check: )
In the case of PSK, ASK and QAM, the modulation alphabet is often conveniently represented on a constellation diagram, showing the amplitude of the I signal at the x-axis, and the amplitude of the Q signal at the y-axis, for each symbol.
Modulate the high-frequency carrier waveform, resulting in that the equivalent low pas signal is frequency shifted into a modulated passband signal or RF signal
The term digital baseband modulation is synonymous to line codes, which are methods to transfer a digital bit stream over an analog lowpass channel using a discrete number of signal levels, by modulating a pulse train (a square wave instead of a sinusoidal waveform).
en.pediax.org /Modulation   (1618 words)

A chromatic pivot-chord modulation is a modulation through the use of a chromatically altered chord, e.g., Neapolitan 6th chord, secondary dominant, secondary diminished 7th chord, and augmented 6th chord.
It is often used in the modulation to chromatically 3rd-related keys, e.g., the use of a sustained note C as a common tone to modulate from C major to Ab major (C is now the 3rd of the new tonic chord).
A sequential modulation by melodic sequences often involves the repetition of a melodic segment, either at the phrase or the sub-phrase level, in a new key a step away from the original key.
music100.music.indiana.edu /som/theory/t511/modulation.html   (513 words)

 Measuring modulation   (Site not responding. Last check: )
The average textbook definition of modulation reads: modulation is a process in which the frequency, phase or amplitude of a carrier wave varies in step with the instantaneous value of the modulating signal.
Modulation measuring equipment has been on the market for a long time, but there are times when a modulation monitor is not available or the monitor's accuracy is in doubt.
As the modulation level increases, the length of the trapezoid's left side decreases as shown in Figure 2b at near 100 percent modulation.
beradio.com /transmission/radio_measuring_modulation   (927 words)

Modulation is the process where a Radio Frequency or Light Wave's amplitude, frequency, or phase is changed in order to transmit intelligence.
In Pulse Amplitude Modulation, a pulse is generated with an amplitude corresponding to that of the modulating waveform.
Also known as Pulse Time Modulation, PPM is a scheme where the pulses of equal amplitude are generated at a rate controlled by the modulating signal's amplitude.
www.k12.hi.us /~telecom/modulation.html   (788 words)

 Amplitude modulation Summary
Amplitude modulation (AM) is a form of modulation in which the amplitude of a carrier wave is varied in direct proportion to that of a modulating signal.
Modulation depth greater than 100% is generally to be avoided - practical transmitter systems will usually incorporate some kind of limiter circuit, such as a VOGAD, to ensure this.
An approach which marries the advantages of low-level modulation with the efficiency of a Class C power amplifier chain is to arrange a feedback system to compensate for the substantial distortion of the AM envelope.
www.bookrags.com /Amplitude_modulation   (1573 words)

Since an FM receiver can only receive--Demodulate--one station at a time (unlike AM which cannot separate interfering stations), that is, two stations on the same frequency, the receiver will only demodulate the stronger of the two [2].
The FM station's signal, as it was entering the receiver's "Front End," was being Modulated by the very strong AM signal.
In effect, the receiver's RF Amplifier was acting as a Detector (rectifier) varying its bias point, which caused the amplifier's gain to change rapidly (at the AM transmitter modulation rate).
www.williamson-labs.com /480_mod.htm   (716 words)

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