INF 680 Syllabus
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hw 3

Read Chapter 3 in the text and Lesson 3 on this web site.  Then, complete this homework assignment and bring it to class.  Work to understand all problems even though all problems may not be assigned.

1. Explain the difference between 'analog' and 'digital' using your own example.

2. Sketch the graph of the time domain for the following sine wave equations:

    a) y = 33 sin(2p 3000 t)
    b) y = 3 sin(2    p 150,000 t)

3. Sketch the graph of the frequency domain for the following equations:

    a) y = 3sin(2p 100 t) + 10sin(2p 100 t)
    b) y = 10sin(2p 70 t) + 10sin(2p 90 t)

4. Fill in the missing information in the following conversion table.

    radians

    degrees

    2pi

    360

    pi

    		  
     

    48

    1.54

    		  

    pi/4

    		  
     

    180
     

    227

    0.95

    		  

5. What is the sine wave equation for the following time and frequency domains?

 

6. What is the period of the following sine wave?

    y = 900 sin(2p 4x106 t)

7. What happens to a square pulse when attenuation, delay distortion and noise intrude upon its transmission?

8. What is the signal to noise ratio, if:

    a) the received signal power is 0.02 mW and the noise power is 500 nW?

    b) a 10W transmitter sends a signal that attenuates 50% by the time it arrives at the receiver and the noise level at the receiver is 700,000 uW?

9. At what power level must a signal be transmitted, on a 12 km cable, to ensure that a minimum Signal to Noise ratio of 10,000:1 is met?  The background noise is 700 nW and 10% of the power is lost per kilometer.

10. Fill in the missing information in the following table.

    y_absolute

    y_dB

    13,000

    		  
     

    175 dBkm2

    46,500,000 V

    		  
     

    -206 dB
     

    10 dBm

    0.000003 mW

    		  
     

    0.1 dBW

    4.452 x 10-8feet

    		  

11. Complete the following

    a) y_dB = 10 dB + 33 dBm - 15 dB
    b) y_dB = 100 dBW + 10 dBm - 15 dBm
    c) y_dB = 10 dBkm + 10 dBkm - 20 dBkm

12. At what power must a signal be transmitted if a signal to noise ratio of 300 dB is required, 10 dB are lost due to attenuation, and the noise level is -60 dBW?

13. What limits the number of bits per symbol and what limits the symbol rate?

14. The signal to noise ratio on your phone line is 1000:1 and your modem attempts 7000 symbols per second, with each symbol representing 6 bits.

    a) What is the data rate that your modem is attempting?

    b) If the bandwidth on the line is 3000 Hz, what is the maximum theoretical data rate?

    c) Check all three limits, show your work.  Which of the three limits were exceeded?


Get some help on problems 9, 11 and 12.

 
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Used with permission of the Author; Copyright (C) Kevin A. Shaffer 1998 - 2022, all rights reserved.