. (symbol), (symbol rate) fT=1/T. (binary) , 0 1.
, . , . (- ) . , , , . (keying), .
- , . . , .
. 6.1. - :
u(t) = Um×cos(2pfot),
-
. 6.1. -. . 6.2. -.
, ( ) ( - fo). . 6.2. , - , .
. 6.3. . 6.4.
. 6.3. , . . 6.4 .
. 6.5
, , . . 40-60 . 6.5.
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, , , . , . . , , .
. , , .
, . 0 1
s0(t) = cos wo(t), s1(t) = cos w1(t),
:
B01(0) = s0(t) s1(t) dt = ½ (sin (ω1+ωo)T)/(ω1+ωo) + ½ (sin (ω1-ωo)T)/(ω1-ωo).
(ω1+ωo)T >> 1 , . (ω1+ωo)T = πk, k = 1, 2,... . , :
Dωmin = p/T, Dfmin = 1/2T = fT/2,
fT .
, . , .
6.6 6.3
(, QAM Quadrature Amplitude Modulation) , . . 8-9, ( ) 256512.
. :
, x (t) y (t) .
(. 6.6).
. 6.6.
y x , () (cos ωt) (sin ωt) . x (t) y (t) Um 2 , , , 90, .. . , (0, π) .
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-4 - (Quadrature Phase Shift Keying QPSK). , (QASK Quadrature Amplitude Shift Keying) ().
( 10 01, 00 11) -4 180 (π). . . , .
(OQPSK - Offset QPSK) 180 , , . OQPSK , -4, , x (t) y (t) , ( . 4.2, , ). , , -4. 180 , , , 0, +90 -90.
. 6.7
. , - - .
, . . . .
, . , , x (t) y (t). , , (signal constellation).
, , m , m 2 . , , ( ) , .
. 6.7 ( ) -16, x (t) y (t) 1, 3 (4- ). . 4.3 , 16 , .
. 6.7
4- . (SPM Superposed Modulation).
, , 4- . SPM , , . 6.7
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(1, 3, 5) , , 62=36. ITU-T 32 .
. 6.8 () () -16
, QAM . , 90. . , m m 2 . . 6.9 -64, , .
, . . , . , . . 6.10 -16 -16 .
. 6.10 -16 -16
d L :
: , . , , =16 (L=4) d=0,471 d=0,390, =32 (L=6) d=0,283, d=0,196.
6.7 6.4. - ( )
- (CAP Carrier less Amplitude Phase modulation) DSL (Digital Subscriber Line) . - . . , . , .
- c , .6.11.
. 6.11 -
. 6.11, F, () fc. (.4.7) fc fc. . fc , . , -, . 6.11. , , . 6.12.
. 6.12. -
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. . , . - , , , , : . /. , DSL SDSL VSDSL.
, , . , , DMT.
6.8 6.5. (DMT-)
(DMT Discrete Multi Tone) , xDSL ADSL VDSL. DMT , , DMT-. , DMT, 256 . 4,3 . DMT . 6.13
. 6.13 DMT
. , , DMT, . ( ) , , -64. , , -4. , , . . .
DMT , . . . . DMT- , . . DMT ANSI ADSL VDSL.