The carrier wave modulation of digital signal

- 2 ≤ of T ／ ／ of T ≤ T 2; ?

CorrespondingBe 0, ± π ／ 2, the circumstance of π , at this moment () =(1, 0) , (0, 1) , (- 1, 0) , (0, - 1) ?

And whenIt is ± π ／ 4, 3 π of ± ／ 4 when () =(1, 1) , (- 1, 1) , (- 1, - 1) , (1, - 1) ?

WithThe point on 2 dimension plane will express, if pursue 5 - 1 is shown. Among them horizontal axisCall inphase axis, vertical axisCall orthogonal axis. Actually the modulation of chroma signal is orthogonal amplitude modulation, just be to use successive signal to go modulation two orthogonality carrier wave just. Say roughly, because be in,2 bit data can convey inside period, the digital rate below identical bandwidth rose one times. To avert the interference between the code, make pulse expands as a result of passageway character namely leave hour of one court decision and cause interference, signal should have plastic according to particular demand, make each adjudicate the dot does not suffer the interference that photograph adjacent piles up, this kind of processing is called balanced adjust. Use the character that has litre of cosine spectrum commonly, at this moment the bandwidth of signal can expand somewhat, the number that because this is below identical bandwidth,transmits leads summary to be less than one times what original transmission number leads. ? ?

If block diagram of QSPK orthogonality modulator pursues 5 - 2 are shown. It can regard as form by two BSPK modulator, the classics of series of news of serial binary system of the input is strung together - alternate, cent becomes the series of two rate halve, n generator arises respectively bipolar I(t) of 2 n signal and Q(t) , be opposite nextUndertake modulation, addition hind gets QPSK signal namely. The picture in the graph gave typical weaveform

? QPSK modulation method is commonly used at going up, next passageways are alternant of type information deferent. ?

? Modulation of 3 orthogonality amplitude (QAM)

If letItself takes different cost, makes processing is orthogonal amplitude modulation (QMA: Quadrature Ampli Tude Modulation) , graph 5 - the 3 constellation that are 16QAM and 32QAM pursue.
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