UNIT I FUNDAMENTALS OF ANALOG COMMUNICATION

UNIT II DIGITAL COMMUNICATIONINTRODUCTION:

FREQUENCY SHIFT KEYING:

UNIT III DIGITAL TRANSMISSIONINTRODUCTION:

Delta Modulation (DM) :

Delta Modulation (DM) :

The modulator consists of a comparator, a quantizer, and an accumulator. The output of the accumulator is

Differential Pulse-Code Modulation (DPCM):Usually PCM has the sampling rate higher than the Nyquist rate .The encode signal

contains redundant information. DPCM can efficiently remove this redundancy.

Figure 3.28 DPCM system. (a) Transmitter. (b) Receiver.

[ ]

[ ] [ ] [ ][ ] [ ][ ] [ ] [ ]

[ ] [ ][ ] size step theis and , of version quantized the

is ,output quantizer theis where

(3.54) 1

(3.53) ) sgn(

(3.52) 1

is signalerror The

).( of sample a is )( and period sampling theis where

,2,1,0 , )(Let

∆

+−=

∆=

−−=

±±==

ne

nenm

nenmnm

nene

nmnmne

tmnTmT

nnTmnm

qq

qqq

q

q

ss

s

Processing Gain:

[ ] [ ] [ ][ ]

[ ] [ ] [ ][ ]

[ ] [ ] [ ] [ ]

[ ][ ] [ ] [ ] (3.78)

(3.77) ˆ

isinput filter prediction The

error.on quantizati is where

(3.75)

isoutput quantizer The

value.prediction a is ˆ

(3.74) ˆ

nqnmnm

nm

nqnenmnm

nq

nqnene

nm

nmnmne

q

q

q

+=⇒

++=

+=

−=

[ ] [ ]

) (minimize G maximize filter to prediction aDesign

(3.82) G Gain, Processing

(3.81) )SNR(

is ratio noiseon quantizati-to-signal theand

error sprediction theof variance theis where

(3.80))SNR(

))(((SNR)

and 0)]][[( of variancesare and where

(3.79) (SNR)

is system DPCM theof (SNR) The

2

2

2

2

2

2

2

2

2

2

o

22

2

2

o

o

Ep

E

Mp

Q

EQ

E

Qp

Q

E

E

M

QM

Q

M

G

nqnmEnm

σσσ

σσ

σ

σσ

σσ

σσ

σσ

=

=

=

=

=

=