• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Pulse-Code Modulation - 14184_136
Figure 2-49.Binary numbers and pulse-code equivalents.

Neets Module 12-Modulation Principles
Page Navigation
  119    120    121    122    123  124  125    126    127    128    129  
2-49 Figure 2-48A.—Quantization levels. MODULATION. Figure 2-48B.—Quantization levels. TIMING. Figure 2-48C.—Quantization levels. QUANTIZED 5-LEVEL. Figure 2-48D.—Quantization levels. QUANTIZED 10-LEVEL. Although the quantization curves of figure 2-48 are based on 5- and 10-level quantization, in actual practice the levels are usually established at some exponential value of 2, such as 4(22),  8(2 3), 16(24), 32(25) . . . N(2n). The reason for selecting levels at exponential values of 2 will become evident in the discussion of pcm. Quantized fm is similar in every way to quantized AM. That is, the range of frequency deviation is divided into a finite number of standard values of deviation. Each sampling pulse results in a deviation equal to the standard value nearest the actual deviation at the sampling instant. Similarly, for phase modulation, quantization establishes a set of standard values. Quantization is used mostly in amplitude- and frequency-modulated pulse systems. Figure 2-49 shows the relationship between decimal numbers, binary numbers, and a pulse-code waveform that represents the numbers. The table is for a 16-level code; that is, 16 standard values of a quantized wave could be represented by these pulse groups. Only the presence or absence of the pulses are important. The next step up would be a 32-level code, with each decimal number represented by a series of five binary digits, rather than the four digits of figure 2-49. Six-digit groups would provide a 64-level code, seven digits a 128-level code, and so forth. Figure 2-50 shows the application of pulse-coded groups to the standard values of a quantized wave.






Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.