Pulse Modulation, Encoding Techniques, and Transmission Codes Sept 19, 2002

Announcement Test #1 next week, from 7:30-8:30 PM. There will be a lecture after the test. Free Grammar Workshops for non-native speakers of English sponsored by the University Writing Center and the English Language Institute. All workshops meet on Wednesdays from 12:30-1:20 PM. Please review WAV files in our class web page that illustrate some quantizing effects.

Homework Homework: –Chapter 5: 2, 4, 5 (use 3100 Hz), 11, 13 (use ) –Chapter 6: Convert the following binary numbers to octal, decimal, and hexadecimal A) B)

Class Objectives Quantization –How do we go from continuous to discrete signal? Encoding –How do we prepare the discrete data for serial transmission? Serial Transmission –How do we get the data from point A to B?

Quantization What is Quantization? –We are sampling a signal and forcing the samples to “fit” into a predetermined set of values. Two Key Factors in Quantizing –Sample Rate –Predefined Levels It is the fundamental technique of all digital telecommunications systems.

Why Quantize? Disadvantages –The resulting signal has less resolution. Sampling gives us just a portion of the original signal We introduce errors in the amplitude of the quantized signal –Therefore, a quantized signal is always of inferior quality than the original signal. If that is so, Then why do we market digital systems as being of superior performance?

Why Quantize? (cont) Advantages –Consistency Signal quality and/or degradation can be “controlled” better than continuous/analog –Data Storage –Signal Processing DSP techniques provide powerful mathematical processes. For example, amplification and filtering can be duplicated reliably over a wide variety of equipment.

FIGURE 5-1 Quantization of an analog signal into 16 discrete levels. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-2 Phase-amplitude modulation (PAM): (a) original signal Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-2 Phase-amplitude modulation (PAM): (b) double-polarity PAM Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-3 Block diagram of a PCM system. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-4 Recovered signals for various sampling rates. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-5 Regeneration of a PCM signal with a regenerative repeater. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-6 (b) quantization of analog signal; (c) quantizing error. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-7 (a) Reconstructed voice pattern without compression Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-7 (b) reconstructed voice pattern with compression, which is much closer to the original signal. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-13 Comparison of PWM, PPM, PAM, and PCM. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-15 Waveforms generated by the delta modulator. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 5-16 Standard encoding techniques. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

Chapter 6

Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 6-1 Electrical impulses for the Baudot character F, transmitted by a Teletype terminal: (a) voltage impulses. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 6-1 Electrical impulses for the Baudot character F, transmitted by a Teletype terminal: (b) current impulses. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 6-3 Typical bar code labels. (Courtesy of Benjamin Nelson, Markem Corp., Keene, H.H.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.

FIGURE 6-4 Basic bar code structure. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey All rights reserved.