Simulink Tutorial on Digital Modulation Methods - Cengage Learning
Simulink Tutorial on Digital Modulation Methods - Cengage Learning Simulink Tutorial on Digital Modulation Methods - Cengage Learning
600 CHAPTER 13. SIMULINK TUTORIAL ON DIGITAL MODULATION SOLUTION 1. The Butterworth lowpass is a partial response filter that in a causal implementation introduces delay. 2. Depends on the noise variance. 3. • The shape of the eye pattern is determined by filtering with the Butterworth filter. Furthermore, noise is present. • The zero ISI condition is not met due to the Butterworth filter. • Optimum sampling time at maximum vertical eye opening. • Since the zero ISI condition is not met, the received signal-space points scatter even if no noise is present. Now you know how to use the software. In the following sections we will describe only new aspects and point out what should be noticed. 13.5.2 Binary Phase Shift Keying with Raised-Cosine Pulses In this section we investigate BPSK with raised-cosine pulses. Choose BPSK > Raised-Cosine Figure 13.36:
13.5. BINARY PHASE-SHIFT KEYING (BPSK) 601 TUTORIAL PROBLEM Figure 13.37: Source signal a(t) Figure 13.38: Baseband signal s(t) Figure 13.39: Transmitted signal u(t) Problem 13.12 [BPSK with Raised-Cosine Pulses] 1. Are the zero ISI condition and the maximum horizontal eye-opening condition met at the transmitter and receiver? 2. What does the answer to question 1 mean for the detection? Consider the eye pattern at the receiver. Does it make sense to use a raised-cosine filter at the transmitter and a matched filter at the receiver? 3. Why is the signal-space trajectory not limited to the range between +1 and −1? 4. How does the transmitted signal u(t) change compared to NRZ rectangular pulses? What is the effect of bandlimitation on the transmitted signal? 5. Compare the source signal a(t) and the sink signal v(t). Are there errors? (Take the filter delays into consideration!) © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
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600 CHAPTER 13. SIMULINK TUTORIAL ON DIGITAL MODULATION<br />
SOLUTION<br />
1. The Butterworth lowpass is a partial resp<strong>on</strong>se filter that in a causal implementati<strong>on</strong><br />
introduces delay.<br />
2. Depends <strong>on</strong> the noise variance.<br />
3. • The shape of the eye pattern is determined by filtering with the Butterworth<br />
filter. Furthermore, noise is present.<br />
• The zero ISI c<strong>on</strong>diti<strong>on</strong> is not met due to the Butterworth filter.<br />
• Optimum sampling time at maximum vertical eye opening.<br />
• Since the zero ISI c<strong>on</strong>diti<strong>on</strong> is not met, the received signal-space points<br />
scatter even if no noise is present.<br />
Now you know how to use the software. In the following secti<strong>on</strong>s we will describe<br />
<strong>on</strong>ly new aspects and point out what should be noticed.<br />
13.5.2 Binary Phase Shift Keying with Raised-Cosine Pulses<br />
In this secti<strong>on</strong> we investigate BPSK with raised-cosine pulses. Choose<br />
BPSK > Raised-Cosine<br />
Figure 13.36: <str<strong>on</strong>g>Simulink</str<strong>on</strong>g> model for BPSK with raised-cosine pulses and matched filter<br />
Figure 13.36 shows the <str<strong>on</strong>g>Simulink</str<strong>on</strong>g> model. The rolloff factor is set to α = 0.5 and the<br />
filter delay is six symbol durati<strong>on</strong>s, 6T. You should keep these settings throughout the<br />
tutorial. However, you can change the settings using a scrollbar which is opened by a<br />
double-click <strong>on</strong> the blue block Rolloff-Factor.<br />
Set the noise variance to a very small value. The time domain signals, eye patterns,<br />
and scatter plots are depicted in Figures 13.37 to 13.46.<br />
© 2013 <strong>Cengage</strong> <strong>Learning</strong>. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
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