, . , .
.
2.1.
u(t) = U(t) cos(ω0t+(t)). (2.1)
(t) , .
U(t) . , (AM) () .
()
(2.2)
. (2.3)
(2.4)
ω0 , (t)
(2.5)
(t) w0, a '(t) - wq .
f0 : fx = N f0, N - . , , :
(2.6)
δ .
:
τ
, (2.7)
<...>- τ.
τ
. (2.8)
τ
. (2.9)
(t), '(t) ԛt,τ 't,τ .
(t): s2, , ,
, (2.10)
>> τ .
(2.7) , (2.10) :
, (2.11)
.. (2.5) (2.7) - .
, , , .
|
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() m ωm =2pFm: :
1)
e(t)=Ec[1+mcosωmt]cosωct (2.12)
m=ka Em /Ec, ka - ,
Ec - , .2.1:
.2.1.
() 0,5 ma Ec /Ec =m/2
, , , ( ) .
2)
e(t)=Eccos (ωct+βsin ωm t), (2.13)
β= kf Em/ ωm =Δf /Fm - ,
Δf - . β<<π/2 .2.2:
e(t) ≈ [ cosωct- β/2 s(ωc- ωm)t + β/2 s(ωc+ ωm)t]
, , π .
, , , 0,5 β E / = β/2.
.2.2.
3 )
e(t)=Ecsin (ωct+θdsin ωm t), (2.14)
θd=k E- .
θd= β = Δf /Fm
: , , . ( ) .
, () 10 lg (β /2)2. ..:
10 lg (Δf /2Fm)2=10lg(Δf / √ 2Fm)2 =20lg(Δf / √ 2Fm),. (2.15)
, :
20 lg (θd /2). (2.16)
, :
- - ;
- - , () , .
, (2.1) :
1. , .
2. S(f): - F 1 ( 1/.).
Ÿ 1. , , . AM , . AM , . S(f) , () .
. Sφ(F) sj2 (2.10) F 1 . , , (). Sφ(F) ,
|
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Sφ(F)=2S (F) [2/] (2.17)
4. Sf(F), sf2 (2.11) F 1 . , ().
Sf(F) = F 2 Sφ(F) = 2 F 2S (F) [2/](2.18)
5. Sy(F) fc = f0
Sν(F) = (F/f0)2 Sφ(F). [ -1 ] (2.19)
Sν(F), 1/ , . .
2 .2.
() , .
, S(F) :
(2.20)
ha - , a ;
Fh - S(F).
, 10-20 ( ). , , 300 ( - 3400 ). FH = 0,01 R, FB= R, R -
. (2.20) , a, .. . . 2.3.
. 2.3.
. 2.1 Sy(F) Sφ(F) (2.20), (2.19)
Sφ(F) = fo2 Sν(F) / F2
2.1
Sν(F) | Sφ(F) | |
h-2F-2 | fo2 h-2 F-4 | |
h-1F-1 | fo2 h-1 F-3 | - |
h0 | fo2 h0 F-2 | |
h1F | fo2 h1 F-1 | - |
h2F2 | fo2 h2 F0 |
.
- . o :
- ;
- .
, , .
1. :
- ( F-2 Sν(F)) (t0, , ..).
- - (F-1 ). . , . , .
- (F0 ) , (, ).
2. :
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- - (F-1 Sφ(F)) y, , .
- (F0 Sφ(F)) , , , . .
, , 4.208.012-77,1979 . .
- , , , .
DA(FH,F)=20lg[Ua(FH,F)/U], (2.21)
U - Up(t) -(2.1) ;
.; (2.22)
ΔU(t)
(2.23)
- ( ),
, (2.24)
Δf(t)
(2.25)
( )
, (2.26)
Δφ(t)
, (2.27)
.
, .. ,
(2.28)
N .
.
, , ( ), :
(2.29)
, :
Δfax =2,58 Δf; Δφ =2,58 Δ φ. (2.29')
, , Δfax = .
, .