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[email protected]
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FM(PM)
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FM
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4.1 4.2 4.3 4.5 4.8 FDM4.9
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4.1
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1(PM)f(t) (KPM)()
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2(FM)f(t) (KFM)()()
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()(), , , , , , f(t) f(t) f(t) f(t) 1)2)()()
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f(t)=Amcosmt
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PMFM12
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4-1 AMFMPM
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4 2
(a)
(b)
PM
d()
dt
f(t)
g(t)
FM
sPM(t)
(b)
sPM(t)
f(t)
(a)
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4 -3
(a)
(b)
FM
sFM(t)
f(t)
(a)
()dt
f(t)
g(t)
PM
sFM(t)
(b)
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(-,) FM
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4-2 KFM =2
(1)fc (2) (3) (4)f(t)
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(4) f(t)(3)
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30(NBFM)(NBPM)(WBFM)(WBPM)4.2
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4.2.1 (NBFM, Narrow Band FM)
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(NBFM)(AM): 1,c 2BFMfmBFM=2fm 3cc+mc-m
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(NBFM)(AM) 1NBFM1/(-c)1/(+c) , 2NBFM180 3NBFMAM
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(NBFM)NBFMAM (AM)
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4 4 AMNBFM
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() 4- 6
+
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-90
f(t)
Acosct
sNBFM(t)
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4-5 AMNBFM
m
m
m
m
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*4.2.2 NBPM
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4- 7
+
-
-90
f(t)
Acosct
sNBPM(t)
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4.3 WBFMwide band FM FM
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4.3.1 1
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, Jn(FM)FMnnn(1)(2)(3)n>1
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4-8 Jn(FM)- FM(1)(2)(3)(n>1)
1.0
0.8
0.6
0.4
0.2
0
-0.2
-0.4
Jn(FM )
FM
1
2
3
4
5
6
7
8
9
10
11
J0
J1
J2
J3
J4
J5
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n(012 nnsFM(t),
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1 2n0AJ0(FM) 3n0cncnmmAJn(FM)
- 4n n 5FM
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4 9 FM=5
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
J-2
J-1
J-3
J0
J1
J3
J2
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
J-2
J-1
J-3
J0
J1
J3
J2
c+nm
-c-nm
J6
J6
J-6
J-6
J4
J4
J-4
J-4
J-5
J-5
J5
J5
BFM
c
-c
...
...
...
...
-
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
J-2
J-1
J-3
J0
J1
J3
J2
c+nm
J6
J-6
J4
J-4
J-5
J5
BFM
c
...
...
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2 nJn(FM)n
nmax
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()1+FM
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4-10 (a) fmfmaxFM
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4-10 (b) fmaxfmFM
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3n=0n0
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?1FM0J0(0)1A2/22FM0J0(FM)1A2/2
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3FMFMPC, Pf PFM
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4-3 2MHz10kHz10kHz(1) (2) (3) (4) fm=10kHzfmax=10kHz(1)
BFM=2(fmax+fm)=2(10+10)=40kHz
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(2) FMFM=2 BFM=2(FM+1)fm=2(2+1)10=60kHz(3) fm=20kHz
BFM=2(fmax+fm)=2(10+20)=60kHz(4) FMfm=20kHz
BFM=2(FM+1)fm=2(1+1)20=80kHz
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44 (1)FM=3A(2)FM=0.5: (1)4 J0(3)-0.260 J1(3)0.339 J2(3)0.486
J3(3)0.309 J4(3)0.132 J5(3)0.043(< 0.1)4-11
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4-11 4-4
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4
99.60.4
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(2)FM=0.5J0(0.5)=0.9385, J1(0.5)=0.242, J2(0.5)=0.0306 1
99.9
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FM AM FMAM AMAMAMAMAM1 FM FMFMFMAM
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4.3.2
4.3.4
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*4.3.4 DFMDFMFMfmaxfm
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4.5 4.5.1 1 4-12
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(VCO, Voltage Controlled Oscillator)
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12
1 2
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4-13
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1L1C4C3LC1C2Cj2
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PLL(PLL ------ Phase locked loop)LC 4 14 PLL
PD
LF
VCO
F(t)
FMPM
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2(NBFM) (4-15) NBFM(WBFM) 4 15
N
f(t)
sNBFM(t)
sWBFM(t)
Acosct
f1, f1, 1
nf1, nf1, n1
n
1
f
1
-
4- 16
+
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-90
f(t)
Acosct
sNBFM(t)
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(n2)- si(t)
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2
2,2
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nnn
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fcfrfc+frfc+frfc-fr4-17
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2
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f0
02(t)FM
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4-5 15kHzf1=200kHzf125Hzf275kHzfo90MHznfr
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f1=25Hzf2=75kHz
90MHz
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418Armstrong f1f11fcfFM, FM
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4 - 18Armstrong
FM
NBFM
n1
cos 2f1t
BPF
n2
f(t)
f1
f1
1
n1 f1
n1f1
n11
cos 2frt
n1 f1-fr
n1f1
fFM
fc
sWBFM(t)
n11
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4-6 4-18 fm=15kHzf1=200kHzf125Hzfr=10.9MHzn1=64n2=48 1 2
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1f1fm
2f1, f2, n1, n2
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4.5.2 ----- -----1.
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-Kd 4 19
(a)
(b)
fc
Kd
(a)
sFM(t)
sd(t)
so(t)
(b)
- KFMf(t)
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1 ,LCfc4-20
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4-21
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LCf0f0fc A(U2m(U2m f(t)(U2m
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LCu2 4-214-20
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24-22
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If01f02 f01 fc= fc-f02uav1uav2
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f(t)=fcD1D2U1m=U2m, f(t)
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u0=uav1-uav24-22U2m~f 4-23f01 f02 4-23
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3PLL 4 24 PLL
PD
VCO
si(t)
sv(t)
uc(t)
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2 4- 25
sNBFM(t)
si(t)
c(t)
sp(t)
sd(t)
fo(t)
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4.8 FDM Frequency Division Multiplex (FDM)(TDM)
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,
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4.8.1
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4-27
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f1(t)
f2(t)
f3(t)
cos1t
cos2t
cos3t
Y()
0
1
2
3
y(t)
0
-m
m
0
-m
m
0
-m
m
F3()
F2()
F1()
-
2
1
3
P1()
0
1
2
3
p1(t)
p2(t)
p3(t)
cos1t
cos2t
cos3t
0
1
2
3
0
1
2
3
P2()
P3()
y(t)
f1(t)
f2(t)
f3(t)
0
-m
m
0
-m
m
0
-m
m
F3()
F2()
F1()
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BsBg Bs3400HzBg600HzB=4kHz
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: :
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4.8.2 4-32
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nnn2n1
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12 121212 n1=3, n2=4 n1+n2=7n1+n2=7n1n2+n2=16 16
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4.8.3
SSB/FM
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4.9 4.9.1 4-1
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4.9.2 535kHz1605KHz3.9MHz18MHz4.5kHZB9kHz
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4.9.3 .,15 KHz,200KHz87MHz108MHz
4.9.4
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4.9.4 4-44
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4.9.7 900 MHZ 900MHZ
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fH3 kHzfmax5kHz B253Bg20kHzBg25 kHz
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1 2V5kHz,PM5 (1)500HZ1kHZ (2)2kHZ6V4.1 (1) , KPM2, f(t) (2) ,
KFM2, f(t) (3)
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4.4 1GHz10kHz10kHz (1) FM (2) (3) (4) 4.8 1kHz
s(t)=100cos(ct+25cosmt)(1) m5(2) m1/5
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4.11 4.112MHz10kHz300kHz
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2
: (1) (2) FM3 10V
: (1)(2)(3)2103Hz
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4 600~4kHzSSBFM2(1)(2)
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4.5 4-1So/NoSin0fm(4.2-18)(4.2-26)(4.2-39)(4.4-8)AM100%1.
WBFMDSBSSBVSBAMNBFMAM
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4-1
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4-31 DSBSSBAM4.7dBFMmf=6AM22 dBFMmfSSB
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WBFMDSBSSBVSBAMNBFMAM FMFM,SSB,
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2. AM AM DSBAM
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SSBAM, AMSSB
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VSB VSBSSBVSB VSBVSB+C(VSB+C)AM SSBDSBVSB
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FM FMFMFMFMFMFMFM
