Simulink Tutorial on Digital Modulation Methods - Cengage Learning

590 CHAPTER 13. SIMULINK TUTORIAL ON DIGITAL MODULATION
2. The maximum horizontal eye opening of T is obtained only for α = 1. The
horizontal eye opening is determined by the transitions +1 →−1 and −1 →+1.
Since for α = 1 the impulse response satisfies
⎧
� � ⎪⎨
1, n = 0
nT
1
g =
2
2 , n =±1
⎪⎩
0, otherwise
the respective lines in the eye pattern are zero at T/2.
3. The bandwidth increases with increasing α. In the time domain the impulse
response is infinite in duration. However, it decreases faster as α decreases.
Now we examine square-root raised-cosine pulses with various roll-off factors (see
Figure 13.18). Choose
from the Pulse Shape menu.
Pulse Shape > Root-RC
Figure 13.18: Impulse response and Fourier transform of a square-root raised-cosine
pulse (α = 0.5)
TUTORIAL PROBLEM
Problem 13.5 [Square-Root RC Pulse]
1. Are the zero ISI condition and the maximum horizontal eye-opening condition
met ?
2. For which rolloff factor are square-root raised-cosine pulses and raised-cosine
pulses identical?
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