( )

Slide *Autor:Seyed Mohammad Reza Razavizadeh

Autor:Seyed Mohammad Reza Razavizadeh

Slide * S/N ( )Signal-to-Noise Ratio (Analog) SNR .C/N ( ) Carrier-to-Noise Ratio (Analog and Digital) .BER ( )

Slide *Information to be sentModulatorMixerMixerTransmitterReceiverInformation receivedDemodulator= Wideband (passband) signal with modulation= Baseband signal with raw informationIFIFRFRF

Slide * S/N dB ITU . SNR 50dB .the Signal power is 100,000 > the Noise power

*Perfect channelWhite noisePhase jitter QAM

Slide *DemodulatorUsers Application DeviceOutput S/N C/N .Input C/N SNR CNR S/N (User Perceives) .

Slide * Bit Error Rate . BER . BER=10-6 106 . - BER

Slide * BER C/N BER : BER . .... C . ... . BER

Slide * AWGN ( ) . BW :

10MHz SNR 30dB

C = BW log2 (1 + SNR)

Slide * +A A :A AT+N0) .(0 1 ).AT: .

(1)

Slide * : (2) :

Slide * (3) Q( ) :

Slide * N0=10-7watt/Hz A=20mV : Rb=1 kbps

Rb=10 kbps A

Slide * (1)

Slide * : :

(1) :

Slide * :

:

(2)Kopt=0.5[s01(T)+s02(T)]

Slide *

:

:

3dB() . : ASK

Slide *

FSK

Slide * PSK

: 0

:

:

Slide * - ISI . Inter Symbol Interference .

() 101101 .() .

Pulse Shaping (1)Slide * : ISI .

Slide * Pulse Shaping (2) . Raised Cosine . . w=1/2TS . :

Pulse Shaping (3)

Slide *

*PSK or QAM

Raised Cosine FSK

Slide * 36MHz QPSK . raised cosine =3 : QPSK ( ) .RS=1/2(36MHz)=18Msym./sec :RS=BW=36MSym/sec

=3 :BW=RS(1+)RS=BW/(1+)=27.7MSym/sec

QPSK 2 27.7x2=55.4Mb/sec .

***********************