Read Chapter 5 in your text and Lesson 5 on this web site. Work to understand all problems even though all problems may not assigned.

1. Using complete sentences written in your own words, explain the meaning of the following:

a) mark

b) bit time

c) duty cycle

d) timing error

2. PCM
A voice signal is measured at 3.21692 V and it resides inside an interval from 3.20 V to 3.30 V.

a)How big is a single interval in volts?

b) If there were 512 levels in the PCM encoder, how many bits would the sample above represent? HINT: L=2ⁿ

c) Receivers have no choice but to decode the the binary sample value at the center of the interval.  So, what would the received voltage of the sample be?

d) If the total range of voltages started at zero and there are 512 intervals, what would the maximum possible voltage be?

e) The original voice signal voltage and the decoded voltage value are different.  What is this "round off error"?

f) What is the ratio of received voltage to round off error in absolute and in dB form?  This is signal to noise ratio for this digital system.

g) In the same system, what would be the value of this ratio for a sample measuring 0.06011 V

h) What would be the data rate of this system if 1500 samples per second are transmitted?

3. Sketch the following bits, 01100, encoded as:

a) ASK

b) FSK

c) PSK

4. Using a combination of ASK, FSK and PSK:

a) Sketch the eight unique signals, one each for 000, 001, 010, 011, 100, 101, 110, and 111.

b) Sketch the transmitted signal for the following bit stream:

10110011 01110100 11000001

c) What would be the data rate of this system if 20,000 signals were sent per second?

d) What would be the effective bit time (not the signal time)?

e) Could this be sent on a channel with a signal to noise ratio of 20 dB and bandwidth of 11,000 Hz?

5. Given the following bit stream, 110010, sketch:

a) Unipolar NRZ with a maximum voltage of +4 V.

b) Bipolar NRZ with a maximum voltage of +5 V.

c) AMI, -3 V to +3 V

d) Manchester from -2 V to +2 V.

6. Encode the following bit stream:

   10000000 00000000 10001100 01110000

a) using HDB3

b) using B8ZS

c) using B6ZS

d) using B3ZS

7. Decode the following bit streams:

a) +000+00- +-00--+- 000-

b) +0+-0-+- 0-+0+-+0 +-0-+

c) +00+-+-0 -+0+-+-0 0-

10. The third sample in the graphic above is 2.3 volts and encoded as a 010.  What range of voltages define the 010 interval?

Used with permission of the Author; Copyright (C) Kevin A. Shaffer 1998 - 2018, all rights reserved.