, . , 11.1, (. . 11.2).
11.2
1 | 2 | (φ) |
00 | ||
900 | ||
1800 | ||
2700 |
- , . N=3, 8 (); N=4 16 .. N =2N . - - (, -4, -8). - 2.
. -4 (, ). 11.15.
: - ; ; ( ); Σ .
11.15 4-
11.16.
bn b(2n) b(2n-1) , . I Q, 11.2
11.16 4-(QPSK)
- .
S(t) = Qcosωt - Isinωt = Scos(ωt + φ)
;
≤ 8, .. ̻ - ().
-4 (-4, Differential Quadrature Phase Shift Keying -DQPSK) 1800 0/0 1/1 1/1 0/0. , , , .
4- π/4 (π/4DQPSK). . 11.15, . 11.17 11.3
11.3
b(2n-1) | b(2n) | Δ φ |
π/4 | ||
3π/4 | ||
-3π/4 | ||
-π/4 |
|
|
4 π/4DQPSK Δφ 0/0, , . 4 450 ( π/4).
11.17 π/4DQPSK
π/4DQPSK 2 , 4-. , .. , 450, . . , 1800 . π/4DQPSK
S(t) = Qcosωt - Isinωt = Scos(ωt + φ-1+Δφ)
φ-1 - Δφ.
, (4-), 0 1800 ( 1800 00). Offset Quadrature Phase Shift Key (OQPSK). OQPSK -4 , Q I , (. .11.18).
11.18
, 11.15 (Q), (I) . , (), , , , -4. 0 1800, OQPSK . 11.19, 1800 QPSK OQPSK.
11.19 QPSK OQPSK c 1800