Digital Modulation Schemes

next up previous
Next: Pulse Modulation Schemes Up: Modulation Schemes Previous: Frequency Modulation

Digital Modulation Schemes

In these schemes one is interested in preparing a digital signal of 1s and 0s for transmission. This signal arises from several sources, for example:

  1. encoding type written characters (ASCII)
  2. sampling and quantizing speech.
  3. sampling and quantizing a video signal.
The simplest digital modulation scheme is called On Off Keying (OOK): here a signal is turned on in response to a 1 and off in response to a 0. This scheme shown in Figure 6 is a very popular scheme for transmitting signals in fiber optic cables.

Figure 6: Showing OOK modulation

Fancier schemes involve modulation in addition to turning a signal on and off.

S Sastry
Sun Apr 20 16:50:27 PDT 1997