() ( )

-

,

.

.

,

,

( ( ):

( )

(Am, A)( )

(f) T = 1/f

(, )

s(t) = A sin(2ft +)s(t) = A sin(2ft +)

( ).

f 3 f (T=1/f)

()

(DC)

( (a

)

.

(Data)

(Signals)

- (Transmission) - (Transmission)

,

,

?

P1 P1 P1 P1 :

PdB = 10log10 (Pa / Pb)

: :

.

NdB=10log (P2/P1) je:

P1 P2

je: NdB = , P1,2 = ,, , log10 = 10.

: NdB=10log (P2/P1) :

(G - Gain) (L - Loss) .

.

P2 = P1*10 **(NdB/10) = 10 log (5/10) = 10 (-0.3) = - 3dB = 10 log (10/5) = 10 (0,3) = 3dB

1: P2=P1 NdB=10log10 (P2/P1) =10 log 10 (P2/P1) = NdB=10 log 10 1 =0

0 100 = 1

(dBW)= 10 log [(W) /1W] (dBW) 10 log [(W) /1W] NdBW=10log10 (P2/ 1W)

(dBmW)= 10 log [(W) /1mW] NdBmW=10log10 (P2/ 1mW)NdBmW 10log10 (P2/ 1mW)

-

P1 = 1 W P1 1 W 1 W.

2: 1 kW (1000 W) 2: 1 kW (1000 W) : NdBW=10log10 (P2/ 1W) =NdBW 10log10 (P2/ 1W) 10log10 (1000/ 1) =10 log10 (103) = 3*10 log10 (10) g ( ) = 30dB

-

3: 1mW (0,001 W) 3: 1mW (0,001 W) : NdBW=10log10 (P2/ 1W) =10log10 (0,001/ 1) =10

log10 (10-3) =(-3)*10 log10 (10)

30d = -30dB

dBi dBi dB(isotropic)

:

: 1 0 0

( )

(

)) -

(Repeaters)(Repeaters) ( ) ( )

LSI/VLSI

(E ti ) (Encryption)

-

+ +

( ) )

2f0 4f0.

( )

.

bps (b/s)

H - Hz

B, 2B

, , B Hz 2B b/s

M

: C= 2B log2M

= 2*tb => f=1/(2*tb) R=1000b/s =>tb=1/1000=1ms, = 2*tb = 2ms, f=1/(2* 10-3) f = 0 5kHz f1 = 0,5kHz

R= 1M b/s => tb=1/ 106 =1s, T = 2*10-6 = 2s, f = 1/(2* 10-6)= f1 = 0,5 MHz

R=1kb/s => f1 = 0,5kHz1 B = 5f1 - f1 = 4 f1 = 4*0,5kHz = 2kHz

R=1Mb/s => f1 = 0,5MHz B = 5f1 - f1 = 4 f1 = 4*0,5kHz = 2MHzB 5f1 f1 4 f1 4 0,5kHz 2MHz

:

, ,

, , ,

, () .

( ) db

db.

SNdB=10 log10 (S/N), dB g10 ( ), S- , N - .

: C = B log2(1+ S/N)C = B log2(1+ S/N)

S/N = 30dB B=3000 Hz S/N = 30dB B=3000 Hz, C=30000 b/s