GNED-135 Study Guide - Amplitude-Shift Keying, Analog Transmission
Document Summary
Figure 5. 3 gives a conceptual view of binary ask. In analog transmission, the sending device produces a high-frequency signal that acts as a base for the information signal. This base signal is called the carrier signal or carrier frequency. The receiving device is tuned to the frequency of the carrier signal that it expects from the sender. Digital information then changes the carrier signal by modifying one or more of its characteristics (amplitude, frequency, or phase). This kind of modification is called modulation (shift keying). In amplitude shift keying, the amplitude of the carrier signal is varied to create signal elements. Both frequency and phase remain constant while the amplitude changes. Although we can have several levels (kinds) of signal elements, each with a different amplitude, ask is normally implemented using only two levels. This is referred to as binary amplitude shift keying or on-off keying (ook).