2010 CS2204 Subject Notes

UNIT I FUNDAMENTALS OF ANALOG COMMUNICATION

UNIT II DIGITAL COMMUNICATION INTRODUCTION:

FREQUENCY SHIFT KEYING:

UNIT III DIGITAL TRANSMISSION INTRODUCTION:

Delta Modulation (DM) :

Delta Modulation (DM) :

Let m[ n ] = m(nT  s ) , n

= 0,±1,±2,



where T  of  m(t ).  s is the sampling  period and m( nT   s ) is a sample The error  signal is e[ n] = m[ n] −mq [ n −1]

(3.52)

eq [ n] = ∆sgn( e[ n] )

(3.53)

mq [ n ] = mq [ n −1] +eq [ n]

(3.54)

where mq [ n] is the quantizer  the quantized

version

output , eq [ n] is

of  e[ n ] , and

∆is

the step size

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.