modulation): Digital signal analog signal
Figure 3.23 Bandwidth of a bandpass channel
If the available channel is a bandpass, i.e., the channel lower bound freq., flow, can be any non zero value, we need to convert our digital signal to anal
Figure 3.16 Two digital signals: one with two signal levels and the other
with four signal levels
Bit Rate: non-periodic digital signals are the most used in digital data transfer, hence period or frequency are not used, ins
Composite Signals: Every composite signal is made of many sine waves of different amps, freqs, phases. (Fourier analysis)
A periodic composite signal can be decomposed into a number of signals with discrete frequencies in the frequency domain.
Figure 3.4 Two signals with the same amplitude and phase,
but different frequencies
Figure 3.5 Three sine waves with the same amplitude and frequency,
but different phases
Wave length: It relates the frequency / period of a signal to it
Data and Signals Data must be transformed to electronic signals (why?)
Analog data:Continuous information, e.g., voice has a value at any time. Analog clock have values at any time!
Digital data: Discrete state information. e.g., digital clock.