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若以 90 % 能量所包括的谱线宽度作为调频信号的带宽,则可以证明调频信号的带宽为 F m = /2 为调制频率, f m =m f •F m 为调制频偏。

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若以 90 % 能量所包括的谱线宽度作为调频信号的带宽,则可以证明调频信号的带宽为 F m = /2 为调制频率, f m =m f •F m 为调制频偏。 若以 99 % 能量计算调频信号的带宽为. u m (t). u FM (t). 电压振荡器 VCC. 信号的调制框图:. 直接调频. u m (t). u FM (t). 积分器. 调相器. f 0. 间接调频. u m (t). u PM (t). 积分器. 调频器. 间接调相. f 0. u FM (t). 前置放大器 B=2(m f +1)F m. r(t). 低频 - PowerPoint PPT Presentation

Text of 若以 90 %...

  • 2.1

  • (AM)(FM)(PM)

  • 1.2.3.(S/N)

  • 2.2

    Uc0

  • (t)

  • Kf

  • Mf(2-7)

    Jk(mf)k

  • FMmf=2) 2B=2(mf+1) Uc Uc/2 J1(mf) J1(mf) J0(mf) J2(mf) J2(mf)

    c

  • 90%

    Fm=/2fm=mfFm99%

  • um(t)uFM(t)f0um(t)f0 uPM(t)

  • Uc,

    Uc>>V(t)

  • u2m(t)

  • Uc
  • 2.2 2.2.1 (FSK){an}, an=1, n=-~+.

    FSK

  • {an}u(t)FSK2FSK) 1 0 0 1 0 1 u(t)

    S(t)=cos(1t+ 1)

    S(t)=cos(2t+2)

  • g(t)Ts

    s(t)

  • g(t)G()P(a=+1)=P(a=-1)=1/2S(t)

  • FSK B=|2-1|+2s (2-26)0 1-s 1 0 2 2+s 2-1Ps()0=(1+2)/2

  • FSK FSKFSK

    12

  • 3.

    X1(t)X2(t)

  • 4.

  • +1

    -1

  • +1-1

  • +1

    -1

  • P(+1)=p(-1), +1

  • erfc(x)

    FSK

  • 2.2.2 MSKFSK=2-1=1/2Tb 120FSK

    Tb

  • MSKh=0.5;h=0.5

  • MSK

    xk t=kTb

  • t=kTb

    (2-35)2-36

  • {ak}MSK

  • MSK:

  • MSK

    MSK

  • sinxk=0 xk 0 22-37

  • xk 0 2 sinxk-1=0, ak-1-ak=0, 2

  • k=2l, l =0,1,2,.,

    IQ2TbTb dk dk=akdk-1 ak=dkdk-1 MSKdk cosxkakcosxk dk

  • (2-37),(2-38),(2-39)MSK:

    yMSK(t)cosxkakcosxk

  • MSK -1 +1 +1 -1 -1 -1 -1 + +1 +1 +1 -1 +1 -1 -1 -1 +10 0 -2 -3 -3 -3 4 -4-4 -4 7 7 7 -7 -7 9 Tb 2 Tb 3Tb 4 Tb 5Tb 6Tb7Tb 8Tb 9Tb10Tb 11Tb12Tb13Tb14Tb15Tb 16Tb Tb 2 Tb 3Tb 4 Tb 5Tb 6Tb7Tb 8Tb 9Tb10Tb 11Tb12Tb13Tb14Tb15Tb 16Tb k dk ak xk cosxk

    akcosxk

    Cosxkcos(t/2Tb)

    akCosxksin(t/2Tb)

  • MSK

    0-10-20-30-40-50-60MSKQPSK

  • MSKMSK [(-c)Tb]-4 MSK

  • MSK

  • 2.MSKBPF

  • 2c1/2Tb P

    T

  • P

    T

  • I

    Q

  • ILPF

    QLPF

  • Pe=2Ps(1-Ps) (2-43) FSK2Tb,

  • 2.2.3 MSK60dB,GMSKMSK

    GMSK (NRZ) h=0.50FM

  • Bb:3db.Tb

  • g(t)g(t)1.0

    0.80.60.40.2

    BbTb= 0.70.40.3-2Tb Tb 0 Tb 2Tb

  • GMSK

  • GMSK:

    MSKGMSK

  • GMSK

  • GMSKGMSK

    cos(t)sin(t)

  • g(t)(2N+1)Tb

    (kTb), (t) (2N+1) (t)cos (t)sin (t)g(t)an(2N+1)Tb

  • 2-15 2-16GSM(- c)Tb=1.560dBBbTbTb( T b BbTb

  • GMSK ()

  • 1.

    R(t)c(t)GMSK

  • LPF

    cTb=k(2)(k)

    R(t)R(t-Tb) b)Y(t)

  • Y(t)>0 +1 Y(t)0, +1 (t)(Tb) sin
  • 2.

    S1F(t)

  • LPF

  • cTb=k(2)(k)

    {}{} Y(t)> +1 Y(t)< -1

  • (2-55) {}

    sin[(t)-(t-Tb)]kcksin[(t-Tb)-(t-2Tb)]ck-1 ck ck-1 ck ck-1 ck=k ck-1 k =ck ck-1

  • (2-20)(2-21)

  • 2.3 2.3.1 (PSK) {an}, an=1, n=-~+. PSK

  • S(t)

    g(t)TbG(), P(+1)=P(-1), PSK

  • PSK

  • 2.

    0

  • PSK

    1.

    y(t)>0 +1 y(t)

  • 2.

  • y(t)>0 +1 y(t)

  • a

    FSK

  • PSKFSK3dBPSKFSK

    2.3.2 (QPSK) (OQPSK)

  • 1. (QPSK)

    2.(OQPSK)

    an

  • anan-1=+1+1

  • an=+1-1n=2k+1

    k=/4, 3/4

  • QPSKPSKd QPSKPSKPSKQPSKOQPSKQPSKOQPSK-1-1

  • QPSK

    //2QQPSKI

  • QPSKOQPSK OQPSKQOQPSKQPSK/2OQPSKQPSK OQPSK

  • 2.3.3 /4-DQPSK/4-DQPSKQPSK/4-DQPSK(QPSK /4-DQPSK/4-DQPSK

  • /4-DQPSK /4-DQPSK

  • kk-1k k = k-1+ k 2-65

  • Uk=cos k = cos (k-1+ k) =cos k-1cos k -sin k-1sin k (2-66)Vk=sin k = sin (k-1+ k) =sin k-1cos k +cos k-1sin k (2-67)Uk-1 =cos k-1 Vk-1 =sin k-1 Uk= Uk-1 cos k - Vk-1 sin k Vk= Vk-1 cos k - Uk-1 sin k (2-68)

  • /4-DQPSK SI SQ k cos k sin k 1 1 /4 1/ 2 1/ 2 -1 1 3/4 -1/ 2 1/ 2 -1 -1 -3/4 -1/ 2 -1/ 2 1 -1 -/4 -1/ 2 -1/ 2

  • /4-DQPSK2-27UkVk

  • LPF

    g(t)/4-DQPSK

  • H()=H0()+H1( ) H()b H0()H1( ) H1( b b + 1 b - 1 H1( )

  • /4-DQPSK

  • 2.4 1941Hedy Lamarr George Antheil#2.292.387WLAN

  • a.; b.c.PNPN(MAI)

  • 2.4.1 PNPNPseudorandom- Noise) 0 1;

  • PNPNm

  • f(x)m2m-1

    2.4.2 (DS-SS)

    M(t): +1-1Ts

  • p(t)PN, +1-1TcTs/Tcc: S(t)Wss; m(t)cos(ct+)B Wss>>Bp(t)B

  • DS-SSSI(t)

  • SI(t)PSKm(t)

    BPF

  • PGPG

  • 2.4.3 (FH-SSFSK

  • Th

  • (FH)

  • 2.4.4 KTs/Tc=NkPNk(t) cos(ct+k)CDMAk

  • i r(t)PN1(t) 2cos(ct+1)m(t)

  • m1,i=-1Zi(1)>0 P[Zi(1)>0| m1,i=-1]r(t)Zi(1)

    I1

  • K-1

    E[2]=N0Ts/4Ikk

  • IkkN

  • Eb/N0

    Pe

  • 2.4.5 FH-SS2FSK2FSK

  • 0.5

    Ph M1/M

  • (K-1)Ph

  • M

    K=1(2-81)2FSKEb/N0(2-84)

  • FH-SS

    Nb

  • (2-86)2-83

  • DS-SSFH-SS DS-SS

  • 2.5 (FDMA)(TDMA)(CDMA)

  • 2.5.1 (FDMA)

  • 25kH30kHz.|f-F|fF(FDD)fF |f-F|800MHz45MHz

  • 2.5.2 (FDD)(TDD)

  • TDMA

  • GSM4.6ms(8 DECT10ms (24 PACS2.5ms (8

  • FDD TDD

  • 3.

  • 2.5.3 (CDMA)(DS-CDMA);(FH-CDMA).Walsh Walsh646464

  • PNmgold242-1m

  • (a) 1 n 1 2 55(b)

  • (

  • DS-CDMA

  • 1.2.c(c+k)3. mf4.

    B=2(mf+1)Fm3kHz

    2-20um(t)mf

    2-20um(t)mf

    =11;-12FSKg(t)01FSKg(t)022(f2-f1)fs(fs=1/Ts)

    FSKFSK2FSKX1(t)>x2(t)+1-1

    nci(t)nsi(t)0n2erfc(x)