0195136047.pdf

712 COMMUNICATION SYSTEMS

Output

Output

L − 1

( 2 )

Midriser

(a)

(b)

Midtread

δv

L − 1

( 2 )δv

≈

≈

≈

≈

≈ ≈

≈ ≈

L − 2

2

5 δv

2

3 δv

2

3 δv

2

( )δv

L − 2

( 2 )δv

−

L − 2

( 2 )δv

L − 2

( 2 )δv

−

L − 1

−( 2 )δv

L − 1

−( 2 )δv

−

5 δv

−δv

− 2 δv

δv

2 δv

− 2

L even

L odd

f(t)

f(t)

Figure 15.3.2Uniform quantizer

characteristics.(a)Midriser with

evenL.(b)Midtread with oddL.

EXAMPLE 15.3.1

A uniform quantizer is said to have 16 levels, and hence is called a midriser. The saturation levels

are to correspond to extreme values of the message of 1 V≤f(t)≤17 V. Find the quantum

levels.

Solution

The tread width isδv = ( 17 − 1 )/ 16 = 1 V. The first quantum level is then given by

1 +(δv/ 2 )= 1 .5 V. Other quantum levels, denoted byli, are given by

li= 1. 5 +(i− 1 )δv= 1. 5 +(i− 1 ) 1 ,i= 1 , 2 ,..., 16