; , (. Carrier Wave ( CW) Modulation);

: . , . ( ).

( ) ( ); ;

fc , fm ;

:

. -. : SC (suppressed carrier); (double-sideband SCDSB); single-sideband (SSB); (vestigal-sideband (VSB)).

:

SCDSB (50%). , ;SSB ();VSB , . . .

(FM) () ;

FM ( ). FM . , , 15 kHz 200 kHz. FM . FSK (phase shift keying). GSM . .

(PM) (FM), ; FM; (. binary phase shift keying (BPSK)), 0 ( ) 180 ( );

QPSK 4 : 0 (00), 90 (01), 180 (10) 270 (01);8-PSK 3 8 ;QAM . . 16-QAM 3 12 ;DVB (Digital Video Broadcasting) - 64-QAM; .

BPSK QPSK:

8-PSK 16-QAM:

:

; ( ). , ; ( ). 100 MHz.

, ; , ; . . ( ). r baud/s : B > r/2.

:

sinc(x)=sin(x)/x, (x=t/W, t )

t=nW/2, . W = B. r = 1/ = 2B

. . 4 : 00, 01, 10, 11. sinc ( , ). (bit/s) (baud/s):rb = kr k .

:

Shannon 1948:C = Blog2(1 + S/N) C bit/s, B Hz, S/N /. , . , .

:r < B 16-QAM 16-BPSK.

; , , ; , S/N. . ;

: . , ; ( ); ;

: :

Nonreturn to Zero (NRZ) 0 1. , ;Return to Zero (RZ) . , 0. , ;Alternate Mark Inversion (AMI) 1 ;High-Density Bipolar 3 . 3 , ;Manchester 1 + , 0 +.

:

; . . 3 dB S/N 0.001; .

:

64 Kbit/s PCM :

. ;FDM (Frequency-Division Multiplexing) , . DM (Time-Division Multiplexing) .

FDM TDM

PCM PCM ; 32 , 30 . , 16 ; 2,048 Kbit/s. 50 ppm (50 parts per million); 1/8000 s = 125 s. 8 .

PCM :

PCMa ; : (. frame alignment word (FAW)) (D4, D5, D6, D7, D8 ); cyclic redundancy check 4 (CRC-4) (C- ) FAW ; D2 0-1-0-1-0-1- ... ;

PCMa:

PCMa 1544 Kbit/s. 24 8 ; , 6- . 1 (. S-bit) . () 12 . 6 S-bit , 6 ;

PCM

PDH (Plesiochronous Digital Hierarchy); 4 . -0, -1, -2, -3, -4, 64 Kbit/s, 2, 8, 34, 140 Mbit/s. -2 20 ppm (100 b/s); . , , . justification.

PDH ( ):

PDH ( ):