- Industry: Telecommunications
- Number of terms: 29235
- Number of blossaries: 0
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ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven standards for the information, entertainment and communications industry.
Modulation in which (a) a subcarrier is modulated with an information-bearing signal and (b) the resulting modulated subcarrier is then used to modulate another carrier that has a higher frequency.
Industry:Telecommunications
Modulation in which (a) an audio frequency band is split into two sub-bands, i.e., a higher and a lower band, and (b) the signals in each sub-band are encoded using ADPCM.
Industry:Telecommunications
Modulation in which a signal is sampled, and the magnitude (with respect to a fixed reference) of each sample is quantized and digitized for transmission over a common transmission medium. Note 1: In conventional PCM, before being digitized, the analog data may be processed (e.g., compressed,) but once digitized, the PCM signal is not subjected to further processing (e.g., digital compaction) before being multiplexed into the aggregate data stream. Note 2: PCM pulse trains may be interleaved with pulse trains from other channels.
Industry:Telecommunications
Modulation in which the amplitude of a carrier wave is varied in accordance with some characteristic of the modulating signal. Note: Amplitude modulation implies the modulation of a coherent carrier wave by mixing it in a nonlinear device with the modulating signal to produce discrete upper and lower sidebands, which are the sum and difference frequencies of the carrier and signal. The envelope of the resultant modulated wave is an analog of the modulating signal. The instantaneous value of the resultant modulated wave is the vector sum of the corresponding instantaneous values of the carrier wave, upper sideband, and lower sideband. Recovery of the modulating signal may be by direct detection or by heterodyning.
Industry:Telecommunications
Modulation in which the amplitude of individual, regularly spaced pulses in a pulse train is varied in accordance with some characteristic of the modulating signal. Note: The amplitude of the amplitude-modulated pulses conveys the information.
Industry:Telecommunications
Modulation in which the choice of the significant condition for any signal element is dependent on the significant condition for the previous signal element. Note: An example of differential modulation is delta modulation.
Industry:Telecommunications
Modulation in which the duration of pulses is varied in accordance with some characteristic of the modulating signal. Deprecated synonyms pulse-length modulation, pulse-width modulation.
Industry:Telecommunications
Modulation in which the instantaneous frequency of a sine wave carrier is caused to depart from the center frequency by an amount proportional to the instantaneous value of the modulating signal. Note 1: In FM, the carrier frequency is called the center frequency. Note 2: FM is a form of angle modulation. Note 3: In optical communications, even if the electrical baseband signal is used to frequency-modulate an electrical carrier (an "FM" optical communications system,) it is still the intensity of the lightwave that is varied (modulated) by the electrical FM carrier. In this case, the "information," as far as the lightwave is concerned, is the electrical FM carrier. The lightwave is varied in intensity at an instantaneous rate corresponding to the instantaneous frequency of the electrical FM carrier.
Industry:Telecommunications
Modulation in which the instantaneous phase of the modulated wave is shifted between a set of predetermined discrete values in accordance with the significant conditions of the modulating signal.
Industry:Telecommunications
Modulation in which the phase or frequency of a sinusoidal carrier is varied. Note: Phase and frequency modulation are particular forms of angle modulation.
Industry:Telecommunications
